Commit | Line | Data |
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20c8ccb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
86039bd3 AA |
2 | /* |
3 | * fs/userfaultfd.c | |
4 | * | |
5 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
6 | * Copyright (C) 2008-2009 Red Hat, Inc. | |
7 | * Copyright (C) 2015 Red Hat, Inc. | |
8 | * | |
86039bd3 AA |
9 | * Some part derived from fs/eventfd.c (anon inode setup) and |
10 | * mm/ksm.c (mm hashing). | |
11 | */ | |
12 | ||
9cd75c3c | 13 | #include <linux/list.h> |
86039bd3 | 14 | #include <linux/hashtable.h> |
174cd4b1 | 15 | #include <linux/sched/signal.h> |
6e84f315 | 16 | #include <linux/sched/mm.h> |
86039bd3 | 17 | #include <linux/mm.h> |
17fca131 | 18 | #include <linux/mm_inline.h> |
6dfeaff9 | 19 | #include <linux/mmu_notifier.h> |
86039bd3 AA |
20 | #include <linux/poll.h> |
21 | #include <linux/slab.h> | |
22 | #include <linux/seq_file.h> | |
23 | #include <linux/file.h> | |
24 | #include <linux/bug.h> | |
25 | #include <linux/anon_inodes.h> | |
26 | #include <linux/syscalls.h> | |
27 | #include <linux/userfaultfd_k.h> | |
28 | #include <linux/mempolicy.h> | |
29 | #include <linux/ioctl.h> | |
30 | #include <linux/security.h> | |
cab350af | 31 | #include <linux/hugetlb.h> |
5c041f5d | 32 | #include <linux/swapops.h> |
2d5de004 | 33 | #include <linux/miscdevice.h> |
86039bd3 | 34 | |
d0d4730a | 35 | int sysctl_unprivileged_userfaultfd __read_mostly; |
cefdca0a | 36 | |
3004ec9c AA |
37 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
38 | ||
3004ec9c AA |
39 | /* |
40 | * Start with fault_pending_wqh and fault_wqh so they're more likely | |
41 | * to be in the same cacheline. | |
cbcfa130 EB |
42 | * |
43 | * Locking order: | |
44 | * fd_wqh.lock | |
45 | * fault_pending_wqh.lock | |
46 | * fault_wqh.lock | |
47 | * event_wqh.lock | |
48 | * | |
49 | * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, | |
50 | * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's | |
51 | * also taken in IRQ context. | |
3004ec9c | 52 | */ |
86039bd3 | 53 | struct userfaultfd_ctx { |
15b726ef AA |
54 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
55 | wait_queue_head_t fault_pending_wqh; | |
56 | /* waitqueue head for the userfaults */ | |
86039bd3 AA |
57 | wait_queue_head_t fault_wqh; |
58 | /* waitqueue head for the pseudo fd to wakeup poll/read */ | |
59 | wait_queue_head_t fd_wqh; | |
9cd75c3c PE |
60 | /* waitqueue head for events */ |
61 | wait_queue_head_t event_wqh; | |
2c5b7e1b | 62 | /* a refile sequence protected by fault_pending_wqh lock */ |
2ca97ac8 | 63 | seqcount_spinlock_t refile_seq; |
3004ec9c | 64 | /* pseudo fd refcounting */ |
ca880420 | 65 | refcount_t refcount; |
86039bd3 AA |
66 | /* userfaultfd syscall flags */ |
67 | unsigned int flags; | |
9cd75c3c PE |
68 | /* features requested from the userspace */ |
69 | unsigned int features; | |
86039bd3 AA |
70 | /* released */ |
71 | bool released; | |
df2cc96e | 72 | /* memory mappings are changing because of non-cooperative event */ |
a759a909 | 73 | atomic_t mmap_changing; |
86039bd3 AA |
74 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
75 | struct mm_struct *mm; | |
76 | }; | |
77 | ||
893e26e6 PE |
78 | struct userfaultfd_fork_ctx { |
79 | struct userfaultfd_ctx *orig; | |
80 | struct userfaultfd_ctx *new; | |
81 | struct list_head list; | |
82 | }; | |
83 | ||
897ab3e0 MR |
84 | struct userfaultfd_unmap_ctx { |
85 | struct userfaultfd_ctx *ctx; | |
86 | unsigned long start; | |
87 | unsigned long end; | |
88 | struct list_head list; | |
89 | }; | |
90 | ||
86039bd3 | 91 | struct userfaultfd_wait_queue { |
a9b85f94 | 92 | struct uffd_msg msg; |
ac6424b9 | 93 | wait_queue_entry_t wq; |
86039bd3 | 94 | struct userfaultfd_ctx *ctx; |
15a77c6f | 95 | bool waken; |
86039bd3 AA |
96 | }; |
97 | ||
98 | struct userfaultfd_wake_range { | |
99 | unsigned long start; | |
100 | unsigned long len; | |
101 | }; | |
102 | ||
22e5fe2a NA |
103 | /* internal indication that UFFD_API ioctl was successfully executed */ |
104 | #define UFFD_FEATURE_INITIALIZED (1u << 31) | |
105 | ||
106 | static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx) | |
107 | { | |
108 | return ctx->features & UFFD_FEATURE_INITIALIZED; | |
109 | } | |
110 | ||
51d3d5eb DH |
111 | static void userfaultfd_set_vm_flags(struct vm_area_struct *vma, |
112 | vm_flags_t flags) | |
113 | { | |
114 | const bool uffd_wp_changed = (vma->vm_flags ^ flags) & VM_UFFD_WP; | |
115 | ||
116 | vma->vm_flags = flags; | |
117 | /* | |
118 | * For shared mappings, we want to enable writenotify while | |
119 | * userfaultfd-wp is enabled (see vma_wants_writenotify()). We'll simply | |
120 | * recalculate vma->vm_page_prot whenever userfaultfd-wp changes. | |
121 | */ | |
122 | if ((vma->vm_flags & VM_SHARED) && uffd_wp_changed) | |
123 | vma_set_page_prot(vma); | |
124 | } | |
125 | ||
ac6424b9 | 126 | static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, |
86039bd3 AA |
127 | int wake_flags, void *key) |
128 | { | |
129 | struct userfaultfd_wake_range *range = key; | |
130 | int ret; | |
131 | struct userfaultfd_wait_queue *uwq; | |
132 | unsigned long start, len; | |
133 | ||
134 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
135 | ret = 0; | |
86039bd3 AA |
136 | /* len == 0 means wake all */ |
137 | start = range->start; | |
138 | len = range->len; | |
a9b85f94 AA |
139 | if (len && (start > uwq->msg.arg.pagefault.address || |
140 | start + len <= uwq->msg.arg.pagefault.address)) | |
86039bd3 | 141 | goto out; |
15a77c6f AA |
142 | WRITE_ONCE(uwq->waken, true); |
143 | /* | |
a9668cd6 PZ |
144 | * The Program-Order guarantees provided by the scheduler |
145 | * ensure uwq->waken is visible before the task is woken. | |
15a77c6f | 146 | */ |
86039bd3 | 147 | ret = wake_up_state(wq->private, mode); |
a9668cd6 | 148 | if (ret) { |
86039bd3 AA |
149 | /* |
150 | * Wake only once, autoremove behavior. | |
151 | * | |
a9668cd6 PZ |
152 | * After the effect of list_del_init is visible to the other |
153 | * CPUs, the waitqueue may disappear from under us, see the | |
154 | * !list_empty_careful() in handle_userfault(). | |
155 | * | |
156 | * try_to_wake_up() has an implicit smp_mb(), and the | |
157 | * wq->private is read before calling the extern function | |
158 | * "wake_up_state" (which in turns calls try_to_wake_up). | |
86039bd3 | 159 | */ |
2055da97 | 160 | list_del_init(&wq->entry); |
a9668cd6 | 161 | } |
86039bd3 AA |
162 | out: |
163 | return ret; | |
164 | } | |
165 | ||
166 | /** | |
167 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd | |
168 | * context. | |
169 | * @ctx: [in] Pointer to the userfaultfd context. | |
86039bd3 AA |
170 | */ |
171 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) | |
172 | { | |
ca880420 | 173 | refcount_inc(&ctx->refcount); |
86039bd3 AA |
174 | } |
175 | ||
176 | /** | |
177 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd | |
178 | * context. | |
179 | * @ctx: [in] Pointer to userfaultfd context. | |
180 | * | |
181 | * The userfaultfd context reference must have been previously acquired either | |
182 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). | |
183 | */ | |
184 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) | |
185 | { | |
ca880420 | 186 | if (refcount_dec_and_test(&ctx->refcount)) { |
86039bd3 AA |
187 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
188 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); | |
189 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); | |
190 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); | |
9cd75c3c PE |
191 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
192 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); | |
86039bd3 AA |
193 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
194 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); | |
d2005e3f | 195 | mmdrop(ctx->mm); |
3004ec9c | 196 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
86039bd3 AA |
197 | } |
198 | } | |
199 | ||
a9b85f94 | 200 | static inline void msg_init(struct uffd_msg *msg) |
86039bd3 | 201 | { |
a9b85f94 AA |
202 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
203 | /* | |
204 | * Must use memset to zero out the paddings or kernel data is | |
205 | * leaked to userland. | |
206 | */ | |
207 | memset(msg, 0, sizeof(struct uffd_msg)); | |
208 | } | |
209 | ||
210 | static inline struct uffd_msg userfault_msg(unsigned long address, | |
d172b1a3 | 211 | unsigned long real_address, |
a9b85f94 | 212 | unsigned int flags, |
9d4ac934 AP |
213 | unsigned long reason, |
214 | unsigned int features) | |
a9b85f94 AA |
215 | { |
216 | struct uffd_msg msg; | |
d172b1a3 | 217 | |
a9b85f94 AA |
218 | msg_init(&msg); |
219 | msg.event = UFFD_EVENT_PAGEFAULT; | |
824ddc60 | 220 | |
d172b1a3 NA |
221 | msg.arg.pagefault.address = (features & UFFD_FEATURE_EXACT_ADDRESS) ? |
222 | real_address : address; | |
223 | ||
7677f7fd AR |
224 | /* |
225 | * These flags indicate why the userfault occurred: | |
226 | * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault. | |
227 | * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault. | |
228 | * - Neither of these flags being set indicates a MISSING fault. | |
229 | * | |
230 | * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write | |
231 | * fault. Otherwise, it was a read fault. | |
232 | */ | |
86039bd3 | 233 | if (flags & FAULT_FLAG_WRITE) |
a9b85f94 | 234 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
86039bd3 | 235 | if (reason & VM_UFFD_WP) |
a9b85f94 | 236 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
7677f7fd AR |
237 | if (reason & VM_UFFD_MINOR) |
238 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR; | |
9d4ac934 | 239 | if (features & UFFD_FEATURE_THREAD_ID) |
a36985d3 | 240 | msg.arg.pagefault.feat.ptid = task_pid_vnr(current); |
a9b85f94 | 241 | return msg; |
86039bd3 AA |
242 | } |
243 | ||
369cd212 MK |
244 | #ifdef CONFIG_HUGETLB_PAGE |
245 | /* | |
246 | * Same functionality as userfaultfd_must_wait below with modifications for | |
247 | * hugepmd ranges. | |
248 | */ | |
249 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 250 | struct vm_area_struct *vma, |
369cd212 MK |
251 | unsigned long address, |
252 | unsigned long flags, | |
253 | unsigned long reason) | |
254 | { | |
1e2c0436 | 255 | pte_t *ptep, pte; |
369cd212 MK |
256 | bool ret = true; |
257 | ||
9c67a207 | 258 | mmap_assert_locked(ctx->mm); |
1e2c0436 | 259 | |
9c67a207 | 260 | ptep = hugetlb_walk(vma, address, vma_mmu_pagesize(vma)); |
1e2c0436 | 261 | if (!ptep) |
369cd212 MK |
262 | goto out; |
263 | ||
264 | ret = false; | |
1e2c0436 | 265 | pte = huge_ptep_get(ptep); |
369cd212 MK |
266 | |
267 | /* | |
268 | * Lockless access: we're in a wait_event so it's ok if it | |
5c041f5d PX |
269 | * changes under us. PTE markers should be handled the same as none |
270 | * ptes here. | |
369cd212 | 271 | */ |
5c041f5d | 272 | if (huge_pte_none_mostly(pte)) |
369cd212 | 273 | ret = true; |
1e2c0436 | 274 | if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) |
369cd212 MK |
275 | ret = true; |
276 | out: | |
277 | return ret; | |
278 | } | |
279 | #else | |
280 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 281 | struct vm_area_struct *vma, |
369cd212 MK |
282 | unsigned long address, |
283 | unsigned long flags, | |
284 | unsigned long reason) | |
285 | { | |
286 | return false; /* should never get here */ | |
287 | } | |
288 | #endif /* CONFIG_HUGETLB_PAGE */ | |
289 | ||
8d2afd96 AA |
290 | /* |
291 | * Verify the pagetables are still not ok after having reigstered into | |
292 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any | |
293 | * userfault that has already been resolved, if userfaultfd_read and | |
294 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different | |
295 | * threads. | |
296 | */ | |
297 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, | |
298 | unsigned long address, | |
299 | unsigned long flags, | |
300 | unsigned long reason) | |
301 | { | |
302 | struct mm_struct *mm = ctx->mm; | |
303 | pgd_t *pgd; | |
c2febafc | 304 | p4d_t *p4d; |
8d2afd96 AA |
305 | pud_t *pud; |
306 | pmd_t *pmd, _pmd; | |
307 | pte_t *pte; | |
308 | bool ret = true; | |
309 | ||
42fc5414 | 310 | mmap_assert_locked(mm); |
8d2afd96 AA |
311 | |
312 | pgd = pgd_offset(mm, address); | |
313 | if (!pgd_present(*pgd)) | |
314 | goto out; | |
c2febafc KS |
315 | p4d = p4d_offset(pgd, address); |
316 | if (!p4d_present(*p4d)) | |
317 | goto out; | |
318 | pud = pud_offset(p4d, address); | |
8d2afd96 AA |
319 | if (!pud_present(*pud)) |
320 | goto out; | |
321 | pmd = pmd_offset(pud, address); | |
322 | /* | |
323 | * READ_ONCE must function as a barrier with narrower scope | |
324 | * and it must be equivalent to: | |
325 | * _pmd = *pmd; barrier(); | |
326 | * | |
327 | * This is to deal with the instability (as in | |
328 | * pmd_trans_unstable) of the pmd. | |
329 | */ | |
330 | _pmd = READ_ONCE(*pmd); | |
a365ac09 | 331 | if (pmd_none(_pmd)) |
8d2afd96 AA |
332 | goto out; |
333 | ||
334 | ret = false; | |
a365ac09 HY |
335 | if (!pmd_present(_pmd)) |
336 | goto out; | |
337 | ||
63b2d417 AA |
338 | if (pmd_trans_huge(_pmd)) { |
339 | if (!pmd_write(_pmd) && (reason & VM_UFFD_WP)) | |
340 | ret = true; | |
8d2afd96 | 341 | goto out; |
63b2d417 | 342 | } |
8d2afd96 AA |
343 | |
344 | /* | |
345 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it | |
346 | * and use the standard pte_offset_map() instead of parsing _pmd. | |
347 | */ | |
348 | pte = pte_offset_map(pmd, address); | |
349 | /* | |
350 | * Lockless access: we're in a wait_event so it's ok if it | |
5c041f5d PX |
351 | * changes under us. PTE markers should be handled the same as none |
352 | * ptes here. | |
8d2afd96 | 353 | */ |
5c041f5d | 354 | if (pte_none_mostly(*pte)) |
8d2afd96 | 355 | ret = true; |
63b2d417 AA |
356 | if (!pte_write(*pte) && (reason & VM_UFFD_WP)) |
357 | ret = true; | |
8d2afd96 AA |
358 | pte_unmap(pte); |
359 | ||
360 | out: | |
361 | return ret; | |
362 | } | |
363 | ||
2f064a59 | 364 | static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags) |
3e69ad08 PX |
365 | { |
366 | if (flags & FAULT_FLAG_INTERRUPTIBLE) | |
367 | return TASK_INTERRUPTIBLE; | |
368 | ||
369 | if (flags & FAULT_FLAG_KILLABLE) | |
370 | return TASK_KILLABLE; | |
371 | ||
372 | return TASK_UNINTERRUPTIBLE; | |
373 | } | |
374 | ||
86039bd3 AA |
375 | /* |
376 | * The locking rules involved in returning VM_FAULT_RETRY depending on | |
377 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and | |
378 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" | |
379 | * recommendation in __lock_page_or_retry is not an understatement. | |
380 | * | |
c1e8d7c6 | 381 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_lock must be released |
86039bd3 AA |
382 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
383 | * not set. | |
384 | * | |
385 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not | |
386 | * set, VM_FAULT_RETRY can still be returned if and only if there are | |
c1e8d7c6 | 387 | * fatal_signal_pending()s, and the mmap_lock must be released before |
86039bd3 AA |
388 | * returning it. |
389 | */ | |
2b740303 | 390 | vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) |
86039bd3 | 391 | { |
b8da2e46 PX |
392 | struct vm_area_struct *vma = vmf->vma; |
393 | struct mm_struct *mm = vma->vm_mm; | |
86039bd3 AA |
394 | struct userfaultfd_ctx *ctx; |
395 | struct userfaultfd_wait_queue uwq; | |
2b740303 | 396 | vm_fault_t ret = VM_FAULT_SIGBUS; |
3e69ad08 | 397 | bool must_wait; |
2f064a59 | 398 | unsigned int blocking_state; |
86039bd3 | 399 | |
64c2b203 AA |
400 | /* |
401 | * We don't do userfault handling for the final child pid update. | |
402 | * | |
403 | * We also don't do userfault handling during | |
404 | * coredumping. hugetlbfs has the special | |
405 | * follow_hugetlb_page() to skip missing pages in the | |
406 | * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with | |
407 | * the no_page_table() helper in follow_page_mask(), but the | |
408 | * shmem_vm_ops->fault method is invoked even during | |
c1e8d7c6 | 409 | * coredumping without mmap_lock and it ends up here. |
64c2b203 AA |
410 | */ |
411 | if (current->flags & (PF_EXITING|PF_DUMPCORE)) | |
412 | goto out; | |
413 | ||
414 | /* | |
c1e8d7c6 ML |
415 | * Coredumping runs without mmap_lock so we can only check that |
416 | * the mmap_lock is held, if PF_DUMPCORE was not set. | |
64c2b203 | 417 | */ |
42fc5414 | 418 | mmap_assert_locked(mm); |
64c2b203 | 419 | |
b8da2e46 | 420 | ctx = vma->vm_userfaultfd_ctx.ctx; |
86039bd3 | 421 | if (!ctx) |
ba85c702 | 422 | goto out; |
86039bd3 AA |
423 | |
424 | BUG_ON(ctx->mm != mm); | |
425 | ||
7677f7fd AR |
426 | /* Any unrecognized flag is a bug. */ |
427 | VM_BUG_ON(reason & ~__VM_UFFD_FLAGS); | |
428 | /* 0 or > 1 flags set is a bug; we expect exactly 1. */ | |
429 | VM_BUG_ON(!reason || (reason & (reason - 1))); | |
86039bd3 | 430 | |
2d6d6f5a PS |
431 | if (ctx->features & UFFD_FEATURE_SIGBUS) |
432 | goto out; | |
2d5de004 | 433 | if (!(vmf->flags & FAULT_FLAG_USER) && (ctx->flags & UFFD_USER_MODE_ONLY)) |
37cd0575 | 434 | goto out; |
2d6d6f5a | 435 | |
86039bd3 AA |
436 | /* |
437 | * If it's already released don't get it. This avoids to loop | |
438 | * in __get_user_pages if userfaultfd_release waits on the | |
c1e8d7c6 | 439 | * caller of handle_userfault to release the mmap_lock. |
86039bd3 | 440 | */ |
6aa7de05 | 441 | if (unlikely(READ_ONCE(ctx->released))) { |
656710a6 AA |
442 | /* |
443 | * Don't return VM_FAULT_SIGBUS in this case, so a non | |
444 | * cooperative manager can close the uffd after the | |
445 | * last UFFDIO_COPY, without risking to trigger an | |
446 | * involuntary SIGBUS if the process was starting the | |
447 | * userfaultfd while the userfaultfd was still armed | |
448 | * (but after the last UFFDIO_COPY). If the uffd | |
449 | * wasn't already closed when the userfault reached | |
450 | * this point, that would normally be solved by | |
451 | * userfaultfd_must_wait returning 'false'. | |
452 | * | |
453 | * If we were to return VM_FAULT_SIGBUS here, the non | |
454 | * cooperative manager would be instead forced to | |
455 | * always call UFFDIO_UNREGISTER before it can safely | |
456 | * close the uffd. | |
457 | */ | |
458 | ret = VM_FAULT_NOPAGE; | |
ba85c702 | 459 | goto out; |
656710a6 | 460 | } |
86039bd3 AA |
461 | |
462 | /* | |
463 | * Check that we can return VM_FAULT_RETRY. | |
464 | * | |
465 | * NOTE: it should become possible to return VM_FAULT_RETRY | |
466 | * even if FAULT_FLAG_TRIED is set without leading to gup() | |
467 | * -EBUSY failures, if the userfaultfd is to be extended for | |
468 | * VM_UFFD_WP tracking and we intend to arm the userfault | |
469 | * without first stopping userland access to the memory. For | |
470 | * VM_UFFD_MISSING userfaults this is enough for now. | |
471 | */ | |
82b0f8c3 | 472 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
86039bd3 AA |
473 | /* |
474 | * Validate the invariant that nowait must allow retry | |
475 | * to be sure not to return SIGBUS erroneously on | |
476 | * nowait invocations. | |
477 | */ | |
82b0f8c3 | 478 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
86039bd3 AA |
479 | #ifdef CONFIG_DEBUG_VM |
480 | if (printk_ratelimit()) { | |
481 | printk(KERN_WARNING | |
82b0f8c3 JK |
482 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
483 | vmf->flags); | |
86039bd3 AA |
484 | dump_stack(); |
485 | } | |
486 | #endif | |
ba85c702 | 487 | goto out; |
86039bd3 AA |
488 | } |
489 | ||
490 | /* | |
491 | * Handle nowait, not much to do other than tell it to retry | |
492 | * and wait. | |
493 | */ | |
ba85c702 | 494 | ret = VM_FAULT_RETRY; |
82b0f8c3 | 495 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
ba85c702 | 496 | goto out; |
86039bd3 | 497 | |
c1e8d7c6 | 498 | /* take the reference before dropping the mmap_lock */ |
86039bd3 AA |
499 | userfaultfd_ctx_get(ctx); |
500 | ||
86039bd3 AA |
501 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
502 | uwq.wq.private = current; | |
d172b1a3 NA |
503 | uwq.msg = userfault_msg(vmf->address, vmf->real_address, vmf->flags, |
504 | reason, ctx->features); | |
86039bd3 | 505 | uwq.ctx = ctx; |
15a77c6f | 506 | uwq.waken = false; |
86039bd3 | 507 | |
3e69ad08 | 508 | blocking_state = userfaultfd_get_blocking_state(vmf->flags); |
dfa37dc3 | 509 | |
b8da2e46 PX |
510 | /* |
511 | * Take the vma lock now, in order to safely call | |
512 | * userfaultfd_huge_must_wait() later. Since acquiring the | |
513 | * (sleepable) vma lock can modify the current task state, that | |
514 | * must be before explicitly calling set_current_state(). | |
515 | */ | |
516 | if (is_vm_hugetlb_page(vma)) | |
517 | hugetlb_vma_lock_read(vma); | |
518 | ||
cbcfa130 | 519 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
520 | /* |
521 | * After the __add_wait_queue the uwq is visible to userland | |
522 | * through poll/read(). | |
523 | */ | |
15b726ef AA |
524 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
525 | /* | |
526 | * The smp_mb() after __set_current_state prevents the reads | |
527 | * following the spin_unlock to happen before the list_add in | |
528 | * __add_wait_queue. | |
529 | */ | |
15a77c6f | 530 | set_current_state(blocking_state); |
cbcfa130 | 531 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 532 | |
b8da2e46 | 533 | if (!is_vm_hugetlb_page(vma)) |
369cd212 MK |
534 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
535 | reason); | |
536 | else | |
b8da2e46 | 537 | must_wait = userfaultfd_huge_must_wait(ctx, vma, |
7868a208 | 538 | vmf->address, |
369cd212 | 539 | vmf->flags, reason); |
b8da2e46 PX |
540 | if (is_vm_hugetlb_page(vma)) |
541 | hugetlb_vma_unlock_read(vma); | |
d8ed45c5 | 542 | mmap_read_unlock(mm); |
8d2afd96 | 543 | |
f9bf3522 | 544 | if (likely(must_wait && !READ_ONCE(ctx->released))) { |
a9a08845 | 545 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
86039bd3 | 546 | schedule(); |
ba85c702 | 547 | } |
86039bd3 | 548 | |
ba85c702 | 549 | __set_current_state(TASK_RUNNING); |
15b726ef AA |
550 | |
551 | /* | |
552 | * Here we race with the list_del; list_add in | |
553 | * userfaultfd_ctx_read(), however because we don't ever run | |
554 | * list_del_init() to refile across the two lists, the prev | |
555 | * and next pointers will never point to self. list_add also | |
556 | * would never let any of the two pointers to point to | |
557 | * self. So list_empty_careful won't risk to see both pointers | |
558 | * pointing to self at any time during the list refile. The | |
559 | * only case where list_del_init() is called is the full | |
560 | * removal in the wake function and there we don't re-list_add | |
561 | * and it's fine not to block on the spinlock. The uwq on this | |
562 | * kernel stack can be released after the list_del_init. | |
563 | */ | |
2055da97 | 564 | if (!list_empty_careful(&uwq.wq.entry)) { |
cbcfa130 | 565 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
15b726ef AA |
566 | /* |
567 | * No need of list_del_init(), the uwq on the stack | |
568 | * will be freed shortly anyway. | |
569 | */ | |
2055da97 | 570 | list_del(&uwq.wq.entry); |
cbcfa130 | 571 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 572 | } |
86039bd3 AA |
573 | |
574 | /* | |
575 | * ctx may go away after this if the userfault pseudo fd is | |
576 | * already released. | |
577 | */ | |
578 | userfaultfd_ctx_put(ctx); | |
579 | ||
ba85c702 AA |
580 | out: |
581 | return ret; | |
86039bd3 AA |
582 | } |
583 | ||
8c9e7bb7 AA |
584 | static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
585 | struct userfaultfd_wait_queue *ewq) | |
9cd75c3c | 586 | { |
0cbb4b4f AA |
587 | struct userfaultfd_ctx *release_new_ctx; |
588 | ||
9a69a829 AA |
589 | if (WARN_ON_ONCE(current->flags & PF_EXITING)) |
590 | goto out; | |
9cd75c3c PE |
591 | |
592 | ewq->ctx = ctx; | |
593 | init_waitqueue_entry(&ewq->wq, current); | |
0cbb4b4f | 594 | release_new_ctx = NULL; |
9cd75c3c | 595 | |
cbcfa130 | 596 | spin_lock_irq(&ctx->event_wqh.lock); |
9cd75c3c PE |
597 | /* |
598 | * After the __add_wait_queue the uwq is visible to userland | |
599 | * through poll/read(). | |
600 | */ | |
601 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); | |
602 | for (;;) { | |
603 | set_current_state(TASK_KILLABLE); | |
604 | if (ewq->msg.event == 0) | |
605 | break; | |
6aa7de05 | 606 | if (READ_ONCE(ctx->released) || |
9cd75c3c | 607 | fatal_signal_pending(current)) { |
384632e6 AA |
608 | /* |
609 | * &ewq->wq may be queued in fork_event, but | |
610 | * __remove_wait_queue ignores the head | |
611 | * parameter. It would be a problem if it | |
612 | * didn't. | |
613 | */ | |
9cd75c3c | 614 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
7eb76d45 MR |
615 | if (ewq->msg.event == UFFD_EVENT_FORK) { |
616 | struct userfaultfd_ctx *new; | |
617 | ||
618 | new = (struct userfaultfd_ctx *) | |
619 | (unsigned long) | |
620 | ewq->msg.arg.reserved.reserved1; | |
0cbb4b4f | 621 | release_new_ctx = new; |
7eb76d45 | 622 | } |
9cd75c3c PE |
623 | break; |
624 | } | |
625 | ||
cbcfa130 | 626 | spin_unlock_irq(&ctx->event_wqh.lock); |
9cd75c3c | 627 | |
a9a08845 | 628 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
9cd75c3c PE |
629 | schedule(); |
630 | ||
cbcfa130 | 631 | spin_lock_irq(&ctx->event_wqh.lock); |
9cd75c3c PE |
632 | } |
633 | __set_current_state(TASK_RUNNING); | |
cbcfa130 | 634 | spin_unlock_irq(&ctx->event_wqh.lock); |
9cd75c3c | 635 | |
0cbb4b4f AA |
636 | if (release_new_ctx) { |
637 | struct vm_area_struct *vma; | |
638 | struct mm_struct *mm = release_new_ctx->mm; | |
69dbe6da | 639 | VMA_ITERATOR(vmi, mm, 0); |
0cbb4b4f AA |
640 | |
641 | /* the various vma->vm_userfaultfd_ctx still points to it */ | |
d8ed45c5 | 642 | mmap_write_lock(mm); |
69dbe6da | 643 | for_each_vma(vmi, vma) { |
31e810aa | 644 | if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { |
0cbb4b4f | 645 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
51d3d5eb DH |
646 | userfaultfd_set_vm_flags(vma, |
647 | vma->vm_flags & ~__VM_UFFD_FLAGS); | |
31e810aa | 648 | } |
69dbe6da | 649 | } |
d8ed45c5 | 650 | mmap_write_unlock(mm); |
0cbb4b4f AA |
651 | |
652 | userfaultfd_ctx_put(release_new_ctx); | |
653 | } | |
654 | ||
9cd75c3c PE |
655 | /* |
656 | * ctx may go away after this if the userfault pseudo fd is | |
657 | * already released. | |
658 | */ | |
9a69a829 | 659 | out: |
a759a909 NA |
660 | atomic_dec(&ctx->mmap_changing); |
661 | VM_BUG_ON(atomic_read(&ctx->mmap_changing) < 0); | |
9cd75c3c | 662 | userfaultfd_ctx_put(ctx); |
9cd75c3c PE |
663 | } |
664 | ||
665 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, | |
666 | struct userfaultfd_wait_queue *ewq) | |
667 | { | |
668 | ewq->msg.event = 0; | |
669 | wake_up_locked(&ctx->event_wqh); | |
670 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
671 | } | |
672 | ||
893e26e6 PE |
673 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
674 | { | |
675 | struct userfaultfd_ctx *ctx = NULL, *octx; | |
676 | struct userfaultfd_fork_ctx *fctx; | |
677 | ||
678 | octx = vma->vm_userfaultfd_ctx.ctx; | |
679 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { | |
680 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
51d3d5eb | 681 | userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS); |
893e26e6 PE |
682 | return 0; |
683 | } | |
684 | ||
685 | list_for_each_entry(fctx, fcs, list) | |
686 | if (fctx->orig == octx) { | |
687 | ctx = fctx->new; | |
688 | break; | |
689 | } | |
690 | ||
691 | if (!ctx) { | |
692 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); | |
693 | if (!fctx) | |
694 | return -ENOMEM; | |
695 | ||
696 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); | |
697 | if (!ctx) { | |
698 | kfree(fctx); | |
699 | return -ENOMEM; | |
700 | } | |
701 | ||
ca880420 | 702 | refcount_set(&ctx->refcount, 1); |
893e26e6 | 703 | ctx->flags = octx->flags; |
893e26e6 PE |
704 | ctx->features = octx->features; |
705 | ctx->released = false; | |
a759a909 | 706 | atomic_set(&ctx->mmap_changing, 0); |
893e26e6 | 707 | ctx->mm = vma->vm_mm; |
00bb31fa | 708 | mmgrab(ctx->mm); |
893e26e6 PE |
709 | |
710 | userfaultfd_ctx_get(octx); | |
a759a909 | 711 | atomic_inc(&octx->mmap_changing); |
893e26e6 PE |
712 | fctx->orig = octx; |
713 | fctx->new = ctx; | |
714 | list_add_tail(&fctx->list, fcs); | |
715 | } | |
716 | ||
717 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
718 | return 0; | |
719 | } | |
720 | ||
8c9e7bb7 | 721 | static void dup_fctx(struct userfaultfd_fork_ctx *fctx) |
893e26e6 PE |
722 | { |
723 | struct userfaultfd_ctx *ctx = fctx->orig; | |
724 | struct userfaultfd_wait_queue ewq; | |
725 | ||
726 | msg_init(&ewq.msg); | |
727 | ||
728 | ewq.msg.event = UFFD_EVENT_FORK; | |
729 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; | |
730 | ||
8c9e7bb7 | 731 | userfaultfd_event_wait_completion(ctx, &ewq); |
893e26e6 PE |
732 | } |
733 | ||
734 | void dup_userfaultfd_complete(struct list_head *fcs) | |
735 | { | |
893e26e6 PE |
736 | struct userfaultfd_fork_ctx *fctx, *n; |
737 | ||
738 | list_for_each_entry_safe(fctx, n, fcs, list) { | |
8c9e7bb7 | 739 | dup_fctx(fctx); |
893e26e6 PE |
740 | list_del(&fctx->list); |
741 | kfree(fctx); | |
742 | } | |
743 | } | |
744 | ||
72f87654 PE |
745 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
746 | struct vm_userfaultfd_ctx *vm_ctx) | |
747 | { | |
748 | struct userfaultfd_ctx *ctx; | |
749 | ||
750 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
3cfd22be PX |
751 | |
752 | if (!ctx) | |
753 | return; | |
754 | ||
755 | if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { | |
72f87654 PE |
756 | vm_ctx->ctx = ctx; |
757 | userfaultfd_ctx_get(ctx); | |
a759a909 | 758 | atomic_inc(&ctx->mmap_changing); |
3cfd22be PX |
759 | } else { |
760 | /* Drop uffd context if remap feature not enabled */ | |
761 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
51d3d5eb | 762 | userfaultfd_set_vm_flags(vma, vma->vm_flags & ~__VM_UFFD_FLAGS); |
72f87654 PE |
763 | } |
764 | } | |
765 | ||
90794bf1 | 766 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
72f87654 PE |
767 | unsigned long from, unsigned long to, |
768 | unsigned long len) | |
769 | { | |
90794bf1 | 770 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
72f87654 PE |
771 | struct userfaultfd_wait_queue ewq; |
772 | ||
773 | if (!ctx) | |
774 | return; | |
775 | ||
776 | if (to & ~PAGE_MASK) { | |
777 | userfaultfd_ctx_put(ctx); | |
778 | return; | |
779 | } | |
780 | ||
781 | msg_init(&ewq.msg); | |
782 | ||
783 | ewq.msg.event = UFFD_EVENT_REMAP; | |
784 | ewq.msg.arg.remap.from = from; | |
785 | ewq.msg.arg.remap.to = to; | |
786 | ewq.msg.arg.remap.len = len; | |
787 | ||
788 | userfaultfd_event_wait_completion(ctx, &ewq); | |
789 | } | |
790 | ||
70ccb92f | 791 | bool userfaultfd_remove(struct vm_area_struct *vma, |
d811914d | 792 | unsigned long start, unsigned long end) |
05ce7724 PE |
793 | { |
794 | struct mm_struct *mm = vma->vm_mm; | |
795 | struct userfaultfd_ctx *ctx; | |
796 | struct userfaultfd_wait_queue ewq; | |
797 | ||
798 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
d811914d | 799 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
70ccb92f | 800 | return true; |
05ce7724 PE |
801 | |
802 | userfaultfd_ctx_get(ctx); | |
a759a909 | 803 | atomic_inc(&ctx->mmap_changing); |
d8ed45c5 | 804 | mmap_read_unlock(mm); |
05ce7724 | 805 | |
05ce7724 PE |
806 | msg_init(&ewq.msg); |
807 | ||
d811914d MR |
808 | ewq.msg.event = UFFD_EVENT_REMOVE; |
809 | ewq.msg.arg.remove.start = start; | |
810 | ewq.msg.arg.remove.end = end; | |
05ce7724 PE |
811 | |
812 | userfaultfd_event_wait_completion(ctx, &ewq); | |
813 | ||
70ccb92f | 814 | return false; |
05ce7724 PE |
815 | } |
816 | ||
897ab3e0 MR |
817 | static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
818 | unsigned long start, unsigned long end) | |
819 | { | |
820 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
821 | ||
822 | list_for_each_entry(unmap_ctx, unmaps, list) | |
823 | if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && | |
824 | unmap_ctx->end == end) | |
825 | return true; | |
826 | ||
827 | return false; | |
828 | } | |
829 | ||
69dbe6da LH |
830 | int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start, |
831 | unsigned long end, struct list_head *unmaps) | |
897ab3e0 | 832 | { |
69dbe6da LH |
833 | VMA_ITERATOR(vmi, mm, start); |
834 | struct vm_area_struct *vma; | |
835 | ||
836 | for_each_vma_range(vmi, vma, end) { | |
897ab3e0 MR |
837 | struct userfaultfd_unmap_ctx *unmap_ctx; |
838 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; | |
839 | ||
840 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || | |
841 | has_unmap_ctx(ctx, unmaps, start, end)) | |
842 | continue; | |
843 | ||
844 | unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); | |
845 | if (!unmap_ctx) | |
846 | return -ENOMEM; | |
847 | ||
848 | userfaultfd_ctx_get(ctx); | |
a759a909 | 849 | atomic_inc(&ctx->mmap_changing); |
897ab3e0 MR |
850 | unmap_ctx->ctx = ctx; |
851 | unmap_ctx->start = start; | |
852 | unmap_ctx->end = end; | |
853 | list_add_tail(&unmap_ctx->list, unmaps); | |
854 | } | |
855 | ||
856 | return 0; | |
857 | } | |
858 | ||
859 | void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) | |
860 | { | |
861 | struct userfaultfd_unmap_ctx *ctx, *n; | |
862 | struct userfaultfd_wait_queue ewq; | |
863 | ||
864 | list_for_each_entry_safe(ctx, n, uf, list) { | |
865 | msg_init(&ewq.msg); | |
866 | ||
867 | ewq.msg.event = UFFD_EVENT_UNMAP; | |
868 | ewq.msg.arg.remove.start = ctx->start; | |
869 | ewq.msg.arg.remove.end = ctx->end; | |
870 | ||
871 | userfaultfd_event_wait_completion(ctx->ctx, &ewq); | |
872 | ||
873 | list_del(&ctx->list); | |
874 | kfree(ctx); | |
875 | } | |
876 | } | |
877 | ||
86039bd3 AA |
878 | static int userfaultfd_release(struct inode *inode, struct file *file) |
879 | { | |
880 | struct userfaultfd_ctx *ctx = file->private_data; | |
881 | struct mm_struct *mm = ctx->mm; | |
882 | struct vm_area_struct *vma, *prev; | |
883 | /* len == 0 means wake all */ | |
884 | struct userfaultfd_wake_range range = { .len = 0, }; | |
885 | unsigned long new_flags; | |
69dbe6da | 886 | MA_STATE(mas, &mm->mm_mt, 0, 0); |
86039bd3 | 887 | |
6aa7de05 | 888 | WRITE_ONCE(ctx->released, true); |
86039bd3 | 889 | |
d2005e3f ON |
890 | if (!mmget_not_zero(mm)) |
891 | goto wakeup; | |
892 | ||
86039bd3 AA |
893 | /* |
894 | * Flush page faults out of all CPUs. NOTE: all page faults | |
895 | * must be retried without returning VM_FAULT_SIGBUS if | |
896 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx | |
c1e8d7c6 | 897 | * changes while handle_userfault released the mmap_lock. So |
86039bd3 | 898 | * it's critical that released is set to true (above), before |
c1e8d7c6 | 899 | * taking the mmap_lock for writing. |
86039bd3 | 900 | */ |
d8ed45c5 | 901 | mmap_write_lock(mm); |
86039bd3 | 902 | prev = NULL; |
69dbe6da | 903 | mas_for_each(&mas, vma, ULONG_MAX) { |
86039bd3 AA |
904 | cond_resched(); |
905 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 906 | !!(vma->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
907 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
908 | prev = vma; | |
909 | continue; | |
910 | } | |
7677f7fd | 911 | new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; |
4d45e75a JH |
912 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
913 | new_flags, vma->anon_vma, | |
914 | vma->vm_file, vma->vm_pgoff, | |
915 | vma_policy(vma), | |
5c26f6ac | 916 | NULL_VM_UFFD_CTX, anon_vma_name(vma)); |
69dbe6da LH |
917 | if (prev) { |
918 | mas_pause(&mas); | |
4d45e75a | 919 | vma = prev; |
69dbe6da | 920 | } else { |
4d45e75a | 921 | prev = vma; |
69dbe6da LH |
922 | } |
923 | ||
51d3d5eb | 924 | userfaultfd_set_vm_flags(vma, new_flags); |
86039bd3 AA |
925 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
926 | } | |
d8ed45c5 | 927 | mmap_write_unlock(mm); |
d2005e3f ON |
928 | mmput(mm); |
929 | wakeup: | |
86039bd3 | 930 | /* |
15b726ef | 931 | * After no new page faults can wait on this fault_*wqh, flush |
86039bd3 | 932 | * the last page faults that may have been already waiting on |
15b726ef | 933 | * the fault_*wqh. |
86039bd3 | 934 | */ |
cbcfa130 | 935 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
ac5be6b4 | 936 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
c430d1e8 | 937 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); |
cbcfa130 | 938 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 939 | |
5a18b64e MR |
940 | /* Flush pending events that may still wait on event_wqh */ |
941 | wake_up_all(&ctx->event_wqh); | |
942 | ||
a9a08845 | 943 | wake_up_poll(&ctx->fd_wqh, EPOLLHUP); |
86039bd3 AA |
944 | userfaultfd_ctx_put(ctx); |
945 | return 0; | |
946 | } | |
947 | ||
15b726ef | 948 | /* fault_pending_wqh.lock must be hold by the caller */ |
6dcc27fd PE |
949 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
950 | wait_queue_head_t *wqh) | |
86039bd3 | 951 | { |
ac6424b9 | 952 | wait_queue_entry_t *wq; |
15b726ef | 953 | struct userfaultfd_wait_queue *uwq; |
86039bd3 | 954 | |
456a7378 | 955 | lockdep_assert_held(&wqh->lock); |
86039bd3 | 956 | |
15b726ef | 957 | uwq = NULL; |
6dcc27fd | 958 | if (!waitqueue_active(wqh)) |
15b726ef AA |
959 | goto out; |
960 | /* walk in reverse to provide FIFO behavior to read userfaults */ | |
2055da97 | 961 | wq = list_last_entry(&wqh->head, typeof(*wq), entry); |
15b726ef AA |
962 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
963 | out: | |
964 | return uwq; | |
86039bd3 | 965 | } |
6dcc27fd PE |
966 | |
967 | static inline struct userfaultfd_wait_queue *find_userfault( | |
968 | struct userfaultfd_ctx *ctx) | |
969 | { | |
970 | return find_userfault_in(&ctx->fault_pending_wqh); | |
971 | } | |
86039bd3 | 972 | |
9cd75c3c PE |
973 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
974 | struct userfaultfd_ctx *ctx) | |
975 | { | |
976 | return find_userfault_in(&ctx->event_wqh); | |
977 | } | |
978 | ||
076ccb76 | 979 | static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) |
86039bd3 AA |
980 | { |
981 | struct userfaultfd_ctx *ctx = file->private_data; | |
076ccb76 | 982 | __poll_t ret; |
86039bd3 AA |
983 | |
984 | poll_wait(file, &ctx->fd_wqh, wait); | |
985 | ||
22e5fe2a | 986 | if (!userfaultfd_is_initialized(ctx)) |
a9a08845 | 987 | return EPOLLERR; |
9cd75c3c | 988 | |
22e5fe2a NA |
989 | /* |
990 | * poll() never guarantees that read won't block. | |
991 | * userfaults can be waken before they're read(). | |
992 | */ | |
993 | if (unlikely(!(file->f_flags & O_NONBLOCK))) | |
a9a08845 | 994 | return EPOLLERR; |
22e5fe2a NA |
995 | /* |
996 | * lockless access to see if there are pending faults | |
997 | * __pollwait last action is the add_wait_queue but | |
998 | * the spin_unlock would allow the waitqueue_active to | |
999 | * pass above the actual list_add inside | |
1000 | * add_wait_queue critical section. So use a full | |
1001 | * memory barrier to serialize the list_add write of | |
1002 | * add_wait_queue() with the waitqueue_active read | |
1003 | * below. | |
1004 | */ | |
1005 | ret = 0; | |
1006 | smp_mb(); | |
1007 | if (waitqueue_active(&ctx->fault_pending_wqh)) | |
1008 | ret = EPOLLIN; | |
1009 | else if (waitqueue_active(&ctx->event_wqh)) | |
1010 | ret = EPOLLIN; | |
1011 | ||
1012 | return ret; | |
86039bd3 AA |
1013 | } |
1014 | ||
893e26e6 PE |
1015 | static const struct file_operations userfaultfd_fops; |
1016 | ||
b537900f DC |
1017 | static int resolve_userfault_fork(struct userfaultfd_ctx *new, |
1018 | struct inode *inode, | |
893e26e6 PE |
1019 | struct uffd_msg *msg) |
1020 | { | |
1021 | int fd; | |
893e26e6 | 1022 | |
b537900f | 1023 | fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new, |
abec3d01 | 1024 | O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); |
893e26e6 PE |
1025 | if (fd < 0) |
1026 | return fd; | |
1027 | ||
893e26e6 PE |
1028 | msg->arg.reserved.reserved1 = 0; |
1029 | msg->arg.fork.ufd = fd; | |
893e26e6 PE |
1030 | return 0; |
1031 | } | |
1032 | ||
86039bd3 | 1033 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
b537900f | 1034 | struct uffd_msg *msg, struct inode *inode) |
86039bd3 AA |
1035 | { |
1036 | ssize_t ret; | |
1037 | DECLARE_WAITQUEUE(wait, current); | |
15b726ef | 1038 | struct userfaultfd_wait_queue *uwq; |
893e26e6 PE |
1039 | /* |
1040 | * Handling fork event requires sleeping operations, so | |
1041 | * we drop the event_wqh lock, then do these ops, then | |
1042 | * lock it back and wake up the waiter. While the lock is | |
1043 | * dropped the ewq may go away so we keep track of it | |
1044 | * carefully. | |
1045 | */ | |
1046 | LIST_HEAD(fork_event); | |
1047 | struct userfaultfd_ctx *fork_nctx = NULL; | |
86039bd3 | 1048 | |
15b726ef | 1049 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
ae62c16e | 1050 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1051 | __add_wait_queue(&ctx->fd_wqh, &wait); |
1052 | for (;;) { | |
1053 | set_current_state(TASK_INTERRUPTIBLE); | |
15b726ef AA |
1054 | spin_lock(&ctx->fault_pending_wqh.lock); |
1055 | uwq = find_userfault(ctx); | |
1056 | if (uwq) { | |
2c5b7e1b AA |
1057 | /* |
1058 | * Use a seqcount to repeat the lockless check | |
1059 | * in wake_userfault() to avoid missing | |
1060 | * wakeups because during the refile both | |
1061 | * waitqueue could become empty if this is the | |
1062 | * only userfault. | |
1063 | */ | |
1064 | write_seqcount_begin(&ctx->refile_seq); | |
1065 | ||
86039bd3 | 1066 | /* |
15b726ef AA |
1067 | * The fault_pending_wqh.lock prevents the uwq |
1068 | * to disappear from under us. | |
1069 | * | |
1070 | * Refile this userfault from | |
1071 | * fault_pending_wqh to fault_wqh, it's not | |
1072 | * pending anymore after we read it. | |
1073 | * | |
1074 | * Use list_del() by hand (as | |
1075 | * userfaultfd_wake_function also uses | |
1076 | * list_del_init() by hand) to be sure nobody | |
1077 | * changes __remove_wait_queue() to use | |
1078 | * list_del_init() in turn breaking the | |
1079 | * !list_empty_careful() check in | |
2055da97 | 1080 | * handle_userfault(). The uwq->wq.head list |
15b726ef AA |
1081 | * must never be empty at any time during the |
1082 | * refile, or the waitqueue could disappear | |
1083 | * from under us. The "wait_queue_head_t" | |
1084 | * parameter of __remove_wait_queue() is unused | |
1085 | * anyway. | |
86039bd3 | 1086 | */ |
2055da97 | 1087 | list_del(&uwq->wq.entry); |
c430d1e8 | 1088 | add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
15b726ef | 1089 | |
2c5b7e1b AA |
1090 | write_seqcount_end(&ctx->refile_seq); |
1091 | ||
a9b85f94 AA |
1092 | /* careful to always initialize msg if ret == 0 */ |
1093 | *msg = uwq->msg; | |
15b726ef | 1094 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1095 | ret = 0; |
1096 | break; | |
1097 | } | |
15b726ef | 1098 | spin_unlock(&ctx->fault_pending_wqh.lock); |
9cd75c3c PE |
1099 | |
1100 | spin_lock(&ctx->event_wqh.lock); | |
1101 | uwq = find_userfault_evt(ctx); | |
1102 | if (uwq) { | |
1103 | *msg = uwq->msg; | |
1104 | ||
893e26e6 PE |
1105 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
1106 | fork_nctx = (struct userfaultfd_ctx *) | |
1107 | (unsigned long) | |
1108 | uwq->msg.arg.reserved.reserved1; | |
2055da97 | 1109 | list_move(&uwq->wq.entry, &fork_event); |
384632e6 AA |
1110 | /* |
1111 | * fork_nctx can be freed as soon as | |
1112 | * we drop the lock, unless we take a | |
1113 | * reference on it. | |
1114 | */ | |
1115 | userfaultfd_ctx_get(fork_nctx); | |
893e26e6 PE |
1116 | spin_unlock(&ctx->event_wqh.lock); |
1117 | ret = 0; | |
1118 | break; | |
1119 | } | |
1120 | ||
9cd75c3c PE |
1121 | userfaultfd_event_complete(ctx, uwq); |
1122 | spin_unlock(&ctx->event_wqh.lock); | |
1123 | ret = 0; | |
1124 | break; | |
1125 | } | |
1126 | spin_unlock(&ctx->event_wqh.lock); | |
1127 | ||
86039bd3 AA |
1128 | if (signal_pending(current)) { |
1129 | ret = -ERESTARTSYS; | |
1130 | break; | |
1131 | } | |
1132 | if (no_wait) { | |
1133 | ret = -EAGAIN; | |
1134 | break; | |
1135 | } | |
ae62c16e | 1136 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1137 | schedule(); |
ae62c16e | 1138 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1139 | } |
1140 | __remove_wait_queue(&ctx->fd_wqh, &wait); | |
1141 | __set_current_state(TASK_RUNNING); | |
ae62c16e | 1142 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1143 | |
893e26e6 | 1144 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
b537900f | 1145 | ret = resolve_userfault_fork(fork_nctx, inode, msg); |
cbcfa130 | 1146 | spin_lock_irq(&ctx->event_wqh.lock); |
384632e6 AA |
1147 | if (!list_empty(&fork_event)) { |
1148 | /* | |
1149 | * The fork thread didn't abort, so we can | |
1150 | * drop the temporary refcount. | |
1151 | */ | |
1152 | userfaultfd_ctx_put(fork_nctx); | |
1153 | ||
1154 | uwq = list_first_entry(&fork_event, | |
1155 | typeof(*uwq), | |
1156 | wq.entry); | |
1157 | /* | |
1158 | * If fork_event list wasn't empty and in turn | |
1159 | * the event wasn't already released by fork | |
1160 | * (the event is allocated on fork kernel | |
1161 | * stack), put the event back to its place in | |
1162 | * the event_wq. fork_event head will be freed | |
1163 | * as soon as we return so the event cannot | |
1164 | * stay queued there no matter the current | |
1165 | * "ret" value. | |
1166 | */ | |
1167 | list_del(&uwq->wq.entry); | |
1168 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); | |
893e26e6 | 1169 | |
384632e6 AA |
1170 | /* |
1171 | * Leave the event in the waitqueue and report | |
1172 | * error to userland if we failed to resolve | |
1173 | * the userfault fork. | |
1174 | */ | |
1175 | if (likely(!ret)) | |
893e26e6 | 1176 | userfaultfd_event_complete(ctx, uwq); |
384632e6 AA |
1177 | } else { |
1178 | /* | |
1179 | * Here the fork thread aborted and the | |
1180 | * refcount from the fork thread on fork_nctx | |
1181 | * has already been released. We still hold | |
1182 | * the reference we took before releasing the | |
1183 | * lock above. If resolve_userfault_fork | |
1184 | * failed we've to drop it because the | |
1185 | * fork_nctx has to be freed in such case. If | |
1186 | * it succeeded we'll hold it because the new | |
1187 | * uffd references it. | |
1188 | */ | |
1189 | if (ret) | |
1190 | userfaultfd_ctx_put(fork_nctx); | |
893e26e6 | 1191 | } |
cbcfa130 | 1192 | spin_unlock_irq(&ctx->event_wqh.lock); |
893e26e6 PE |
1193 | } |
1194 | ||
86039bd3 AA |
1195 | return ret; |
1196 | } | |
1197 | ||
1198 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, | |
1199 | size_t count, loff_t *ppos) | |
1200 | { | |
1201 | struct userfaultfd_ctx *ctx = file->private_data; | |
1202 | ssize_t _ret, ret = 0; | |
a9b85f94 | 1203 | struct uffd_msg msg; |
86039bd3 | 1204 | int no_wait = file->f_flags & O_NONBLOCK; |
b537900f | 1205 | struct inode *inode = file_inode(file); |
86039bd3 | 1206 | |
22e5fe2a | 1207 | if (!userfaultfd_is_initialized(ctx)) |
86039bd3 | 1208 | return -EINVAL; |
86039bd3 AA |
1209 | |
1210 | for (;;) { | |
a9b85f94 | 1211 | if (count < sizeof(msg)) |
86039bd3 | 1212 | return ret ? ret : -EINVAL; |
b537900f | 1213 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode); |
86039bd3 AA |
1214 | if (_ret < 0) |
1215 | return ret ? ret : _ret; | |
a9b85f94 | 1216 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
86039bd3 | 1217 | return ret ? ret : -EFAULT; |
a9b85f94 AA |
1218 | ret += sizeof(msg); |
1219 | buf += sizeof(msg); | |
1220 | count -= sizeof(msg); | |
86039bd3 AA |
1221 | /* |
1222 | * Allow to read more than one fault at time but only | |
1223 | * block if waiting for the very first one. | |
1224 | */ | |
1225 | no_wait = O_NONBLOCK; | |
1226 | } | |
1227 | } | |
1228 | ||
1229 | static void __wake_userfault(struct userfaultfd_ctx *ctx, | |
1230 | struct userfaultfd_wake_range *range) | |
1231 | { | |
cbcfa130 | 1232 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 1233 | /* wake all in the range and autoremove */ |
15b726ef | 1234 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
ac5be6b4 | 1235 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
15b726ef AA |
1236 | range); |
1237 | if (waitqueue_active(&ctx->fault_wqh)) | |
c430d1e8 | 1238 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); |
cbcfa130 | 1239 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1240 | } |
1241 | ||
1242 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, | |
1243 | struct userfaultfd_wake_range *range) | |
1244 | { | |
2c5b7e1b AA |
1245 | unsigned seq; |
1246 | bool need_wakeup; | |
1247 | ||
86039bd3 AA |
1248 | /* |
1249 | * To be sure waitqueue_active() is not reordered by the CPU | |
1250 | * before the pagetable update, use an explicit SMP memory | |
3e4e28c5 | 1251 | * barrier here. PT lock release or mmap_read_unlock(mm) still |
86039bd3 AA |
1252 | * have release semantics that can allow the |
1253 | * waitqueue_active() to be reordered before the pte update. | |
1254 | */ | |
1255 | smp_mb(); | |
1256 | ||
1257 | /* | |
1258 | * Use waitqueue_active because it's very frequent to | |
1259 | * change the address space atomically even if there are no | |
1260 | * userfaults yet. So we take the spinlock only when we're | |
1261 | * sure we've userfaults to wake. | |
1262 | */ | |
2c5b7e1b AA |
1263 | do { |
1264 | seq = read_seqcount_begin(&ctx->refile_seq); | |
1265 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || | |
1266 | waitqueue_active(&ctx->fault_wqh); | |
1267 | cond_resched(); | |
1268 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); | |
1269 | if (need_wakeup) | |
86039bd3 AA |
1270 | __wake_userfault(ctx, range); |
1271 | } | |
1272 | ||
1273 | static __always_inline int validate_range(struct mm_struct *mm, | |
e71e2ace | 1274 | __u64 start, __u64 len) |
86039bd3 AA |
1275 | { |
1276 | __u64 task_size = mm->task_size; | |
1277 | ||
e71e2ace | 1278 | if (start & ~PAGE_MASK) |
86039bd3 AA |
1279 | return -EINVAL; |
1280 | if (len & ~PAGE_MASK) | |
1281 | return -EINVAL; | |
1282 | if (!len) | |
1283 | return -EINVAL; | |
e71e2ace | 1284 | if (start < mmap_min_addr) |
86039bd3 | 1285 | return -EINVAL; |
e71e2ace | 1286 | if (start >= task_size) |
86039bd3 | 1287 | return -EINVAL; |
e71e2ace | 1288 | if (len > task_size - start) |
86039bd3 AA |
1289 | return -EINVAL; |
1290 | return 0; | |
1291 | } | |
1292 | ||
1293 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, | |
1294 | unsigned long arg) | |
1295 | { | |
1296 | struct mm_struct *mm = ctx->mm; | |
1297 | struct vm_area_struct *vma, *prev, *cur; | |
1298 | int ret; | |
1299 | struct uffdio_register uffdio_register; | |
1300 | struct uffdio_register __user *user_uffdio_register; | |
1301 | unsigned long vm_flags, new_flags; | |
1302 | bool found; | |
ce53e8e6 | 1303 | bool basic_ioctls; |
86039bd3 | 1304 | unsigned long start, end, vma_end; |
69dbe6da | 1305 | MA_STATE(mas, &mm->mm_mt, 0, 0); |
86039bd3 AA |
1306 | |
1307 | user_uffdio_register = (struct uffdio_register __user *) arg; | |
1308 | ||
1309 | ret = -EFAULT; | |
1310 | if (copy_from_user(&uffdio_register, user_uffdio_register, | |
1311 | sizeof(uffdio_register)-sizeof(__u64))) | |
1312 | goto out; | |
1313 | ||
1314 | ret = -EINVAL; | |
1315 | if (!uffdio_register.mode) | |
1316 | goto out; | |
7677f7fd | 1317 | if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES) |
86039bd3 AA |
1318 | goto out; |
1319 | vm_flags = 0; | |
1320 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) | |
1321 | vm_flags |= VM_UFFD_MISSING; | |
00b151f2 PX |
1322 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
1323 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP | |
1324 | goto out; | |
1325 | #endif | |
86039bd3 | 1326 | vm_flags |= VM_UFFD_WP; |
00b151f2 | 1327 | } |
7677f7fd AR |
1328 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { |
1329 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR | |
1330 | goto out; | |
1331 | #endif | |
1332 | vm_flags |= VM_UFFD_MINOR; | |
1333 | } | |
86039bd3 | 1334 | |
e71e2ace | 1335 | ret = validate_range(mm, uffdio_register.range.start, |
86039bd3 AA |
1336 | uffdio_register.range.len); |
1337 | if (ret) | |
1338 | goto out; | |
1339 | ||
1340 | start = uffdio_register.range.start; | |
1341 | end = start + uffdio_register.range.len; | |
1342 | ||
d2005e3f ON |
1343 | ret = -ENOMEM; |
1344 | if (!mmget_not_zero(mm)) | |
1345 | goto out; | |
1346 | ||
d8ed45c5 | 1347 | mmap_write_lock(mm); |
69dbe6da LH |
1348 | mas_set(&mas, start); |
1349 | vma = mas_find(&mas, ULONG_MAX); | |
86039bd3 AA |
1350 | if (!vma) |
1351 | goto out_unlock; | |
1352 | ||
1353 | /* check that there's at least one vma in the range */ | |
1354 | ret = -EINVAL; | |
1355 | if (vma->vm_start >= end) | |
1356 | goto out_unlock; | |
1357 | ||
cab350af MK |
1358 | /* |
1359 | * If the first vma contains huge pages, make sure start address | |
1360 | * is aligned to huge page size. | |
1361 | */ | |
1362 | if (is_vm_hugetlb_page(vma)) { | |
1363 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1364 | ||
1365 | if (start & (vma_hpagesize - 1)) | |
1366 | goto out_unlock; | |
1367 | } | |
1368 | ||
86039bd3 AA |
1369 | /* |
1370 | * Search for not compatible vmas. | |
86039bd3 AA |
1371 | */ |
1372 | found = false; | |
ce53e8e6 | 1373 | basic_ioctls = false; |
69dbe6da | 1374 | for (cur = vma; cur; cur = mas_next(&mas, end - 1)) { |
86039bd3 AA |
1375 | cond_resched(); |
1376 | ||
1377 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 1378 | !!(cur->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
1379 | |
1380 | /* check not compatible vmas */ | |
1381 | ret = -EINVAL; | |
63b2d417 | 1382 | if (!vma_can_userfault(cur, vm_flags)) |
86039bd3 | 1383 | goto out_unlock; |
29ec9066 AA |
1384 | |
1385 | /* | |
1386 | * UFFDIO_COPY will fill file holes even without | |
1387 | * PROT_WRITE. This check enforces that if this is a | |
1388 | * MAP_SHARED, the process has write permission to the backing | |
1389 | * file. If VM_MAYWRITE is set it also enforces that on a | |
1390 | * MAP_SHARED vma: there is no F_WRITE_SEAL and no further | |
1391 | * F_WRITE_SEAL can be taken until the vma is destroyed. | |
1392 | */ | |
1393 | ret = -EPERM; | |
1394 | if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) | |
1395 | goto out_unlock; | |
1396 | ||
cab350af MK |
1397 | /* |
1398 | * If this vma contains ending address, and huge pages | |
1399 | * check alignment. | |
1400 | */ | |
1401 | if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && | |
1402 | end > cur->vm_start) { | |
1403 | unsigned long vma_hpagesize = vma_kernel_pagesize(cur); | |
1404 | ||
1405 | ret = -EINVAL; | |
1406 | ||
1407 | if (end & (vma_hpagesize - 1)) | |
1408 | goto out_unlock; | |
1409 | } | |
63b2d417 AA |
1410 | if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) |
1411 | goto out_unlock; | |
86039bd3 AA |
1412 | |
1413 | /* | |
1414 | * Check that this vma isn't already owned by a | |
1415 | * different userfaultfd. We can't allow more than one | |
1416 | * userfaultfd to own a single vma simultaneously or we | |
1417 | * wouldn't know which one to deliver the userfaults to. | |
1418 | */ | |
1419 | ret = -EBUSY; | |
1420 | if (cur->vm_userfaultfd_ctx.ctx && | |
1421 | cur->vm_userfaultfd_ctx.ctx != ctx) | |
1422 | goto out_unlock; | |
1423 | ||
cab350af MK |
1424 | /* |
1425 | * Note vmas containing huge pages | |
1426 | */ | |
ce53e8e6 MR |
1427 | if (is_vm_hugetlb_page(cur)) |
1428 | basic_ioctls = true; | |
cab350af | 1429 | |
86039bd3 AA |
1430 | found = true; |
1431 | } | |
1432 | BUG_ON(!found); | |
1433 | ||
69dbe6da LH |
1434 | mas_set(&mas, start); |
1435 | prev = mas_prev(&mas, 0); | |
1436 | if (prev != vma) | |
1437 | mas_next(&mas, ULONG_MAX); | |
86039bd3 AA |
1438 | |
1439 | ret = 0; | |
1440 | do { | |
1441 | cond_resched(); | |
1442 | ||
63b2d417 | 1443 | BUG_ON(!vma_can_userfault(vma, vm_flags)); |
86039bd3 AA |
1444 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
1445 | vma->vm_userfaultfd_ctx.ctx != ctx); | |
29ec9066 | 1446 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
86039bd3 AA |
1447 | |
1448 | /* | |
1449 | * Nothing to do: this vma is already registered into this | |
1450 | * userfaultfd and with the right tracking mode too. | |
1451 | */ | |
1452 | if (vma->vm_userfaultfd_ctx.ctx == ctx && | |
1453 | (vma->vm_flags & vm_flags) == vm_flags) | |
1454 | goto skip; | |
1455 | ||
1456 | if (vma->vm_start > start) | |
1457 | start = vma->vm_start; | |
1458 | vma_end = min(end, vma->vm_end); | |
1459 | ||
7677f7fd | 1460 | new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags; |
86039bd3 AA |
1461 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
1462 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1463 | vma_policy(vma), | |
9a10064f | 1464 | ((struct vm_userfaultfd_ctx){ ctx }), |
5c26f6ac | 1465 | anon_vma_name(vma)); |
86039bd3 | 1466 | if (prev) { |
69dbe6da LH |
1467 | /* vma_merge() invalidated the mas */ |
1468 | mas_pause(&mas); | |
86039bd3 AA |
1469 | vma = prev; |
1470 | goto next; | |
1471 | } | |
1472 | if (vma->vm_start < start) { | |
1473 | ret = split_vma(mm, vma, start, 1); | |
1474 | if (ret) | |
1475 | break; | |
69dbe6da LH |
1476 | /* split_vma() invalidated the mas */ |
1477 | mas_pause(&mas); | |
86039bd3 AA |
1478 | } |
1479 | if (vma->vm_end > end) { | |
1480 | ret = split_vma(mm, vma, end, 0); | |
1481 | if (ret) | |
1482 | break; | |
69dbe6da LH |
1483 | /* split_vma() invalidated the mas */ |
1484 | mas_pause(&mas); | |
86039bd3 AA |
1485 | } |
1486 | next: | |
1487 | /* | |
1488 | * In the vma_merge() successful mprotect-like case 8: | |
1489 | * the next vma was merged into the current one and | |
1490 | * the current one has not been updated yet. | |
1491 | */ | |
51d3d5eb | 1492 | userfaultfd_set_vm_flags(vma, new_flags); |
86039bd3 AA |
1493 | vma->vm_userfaultfd_ctx.ctx = ctx; |
1494 | ||
6dfeaff9 PX |
1495 | if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) |
1496 | hugetlb_unshare_all_pmds(vma); | |
1497 | ||
86039bd3 AA |
1498 | skip: |
1499 | prev = vma; | |
1500 | start = vma->vm_end; | |
69dbe6da LH |
1501 | vma = mas_next(&mas, end - 1); |
1502 | } while (vma); | |
86039bd3 | 1503 | out_unlock: |
d8ed45c5 | 1504 | mmap_write_unlock(mm); |
d2005e3f | 1505 | mmput(mm); |
86039bd3 | 1506 | if (!ret) { |
14819305 PX |
1507 | __u64 ioctls_out; |
1508 | ||
1509 | ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : | |
1510 | UFFD_API_RANGE_IOCTLS; | |
1511 | ||
1512 | /* | |
1513 | * Declare the WP ioctl only if the WP mode is | |
1514 | * specified and all checks passed with the range | |
1515 | */ | |
1516 | if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) | |
1517 | ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); | |
1518 | ||
f6191471 AR |
1519 | /* CONTINUE ioctl is only supported for MINOR ranges. */ |
1520 | if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR)) | |
1521 | ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE); | |
1522 | ||
86039bd3 AA |
1523 | /* |
1524 | * Now that we scanned all vmas we can already tell | |
1525 | * userland which ioctls methods are guaranteed to | |
1526 | * succeed on this range. | |
1527 | */ | |
14819305 | 1528 | if (put_user(ioctls_out, &user_uffdio_register->ioctls)) |
86039bd3 AA |
1529 | ret = -EFAULT; |
1530 | } | |
1531 | out: | |
1532 | return ret; | |
1533 | } | |
1534 | ||
1535 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, | |
1536 | unsigned long arg) | |
1537 | { | |
1538 | struct mm_struct *mm = ctx->mm; | |
1539 | struct vm_area_struct *vma, *prev, *cur; | |
1540 | int ret; | |
1541 | struct uffdio_range uffdio_unregister; | |
1542 | unsigned long new_flags; | |
1543 | bool found; | |
1544 | unsigned long start, end, vma_end; | |
1545 | const void __user *buf = (void __user *)arg; | |
69dbe6da | 1546 | MA_STATE(mas, &mm->mm_mt, 0, 0); |
86039bd3 AA |
1547 | |
1548 | ret = -EFAULT; | |
1549 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) | |
1550 | goto out; | |
1551 | ||
e71e2ace | 1552 | ret = validate_range(mm, uffdio_unregister.start, |
86039bd3 AA |
1553 | uffdio_unregister.len); |
1554 | if (ret) | |
1555 | goto out; | |
1556 | ||
1557 | start = uffdio_unregister.start; | |
1558 | end = start + uffdio_unregister.len; | |
1559 | ||
d2005e3f ON |
1560 | ret = -ENOMEM; |
1561 | if (!mmget_not_zero(mm)) | |
1562 | goto out; | |
1563 | ||
d8ed45c5 | 1564 | mmap_write_lock(mm); |
69dbe6da LH |
1565 | mas_set(&mas, start); |
1566 | vma = mas_find(&mas, ULONG_MAX); | |
86039bd3 AA |
1567 | if (!vma) |
1568 | goto out_unlock; | |
1569 | ||
1570 | /* check that there's at least one vma in the range */ | |
1571 | ret = -EINVAL; | |
1572 | if (vma->vm_start >= end) | |
1573 | goto out_unlock; | |
1574 | ||
cab350af MK |
1575 | /* |
1576 | * If the first vma contains huge pages, make sure start address | |
1577 | * is aligned to huge page size. | |
1578 | */ | |
1579 | if (is_vm_hugetlb_page(vma)) { | |
1580 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1581 | ||
1582 | if (start & (vma_hpagesize - 1)) | |
1583 | goto out_unlock; | |
1584 | } | |
1585 | ||
86039bd3 AA |
1586 | /* |
1587 | * Search for not compatible vmas. | |
86039bd3 AA |
1588 | */ |
1589 | found = false; | |
1590 | ret = -EINVAL; | |
69dbe6da | 1591 | for (cur = vma; cur; cur = mas_next(&mas, end - 1)) { |
86039bd3 AA |
1592 | cond_resched(); |
1593 | ||
1594 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 1595 | !!(cur->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
1596 | |
1597 | /* | |
1598 | * Check not compatible vmas, not strictly required | |
1599 | * here as not compatible vmas cannot have an | |
1600 | * userfaultfd_ctx registered on them, but this | |
1601 | * provides for more strict behavior to notice | |
1602 | * unregistration errors. | |
1603 | */ | |
63b2d417 | 1604 | if (!vma_can_userfault(cur, cur->vm_flags)) |
86039bd3 AA |
1605 | goto out_unlock; |
1606 | ||
1607 | found = true; | |
1608 | } | |
1609 | BUG_ON(!found); | |
1610 | ||
69dbe6da LH |
1611 | mas_set(&mas, start); |
1612 | prev = mas_prev(&mas, 0); | |
1613 | if (prev != vma) | |
1614 | mas_next(&mas, ULONG_MAX); | |
86039bd3 AA |
1615 | |
1616 | ret = 0; | |
1617 | do { | |
1618 | cond_resched(); | |
1619 | ||
63b2d417 | 1620 | BUG_ON(!vma_can_userfault(vma, vma->vm_flags)); |
86039bd3 AA |
1621 | |
1622 | /* | |
1623 | * Nothing to do: this vma is already registered into this | |
1624 | * userfaultfd and with the right tracking mode too. | |
1625 | */ | |
1626 | if (!vma->vm_userfaultfd_ctx.ctx) | |
1627 | goto skip; | |
1628 | ||
01e881f5 AA |
1629 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
1630 | ||
86039bd3 AA |
1631 | if (vma->vm_start > start) |
1632 | start = vma->vm_start; | |
1633 | vma_end = min(end, vma->vm_end); | |
1634 | ||
09fa5296 AA |
1635 | if (userfaultfd_missing(vma)) { |
1636 | /* | |
1637 | * Wake any concurrent pending userfault while | |
1638 | * we unregister, so they will not hang | |
1639 | * permanently and it avoids userland to call | |
1640 | * UFFDIO_WAKE explicitly. | |
1641 | */ | |
1642 | struct userfaultfd_wake_range range; | |
1643 | range.start = start; | |
1644 | range.len = vma_end - start; | |
1645 | wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); | |
1646 | } | |
1647 | ||
f369b07c PX |
1648 | /* Reset ptes for the whole vma range if wr-protected */ |
1649 | if (userfaultfd_wp(vma)) | |
1650 | uffd_wp_range(mm, vma, start, vma_end - start, false); | |
1651 | ||
7677f7fd | 1652 | new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; |
86039bd3 AA |
1653 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
1654 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1655 | vma_policy(vma), | |
5c26f6ac | 1656 | NULL_VM_UFFD_CTX, anon_vma_name(vma)); |
86039bd3 AA |
1657 | if (prev) { |
1658 | vma = prev; | |
59f2f4b8 | 1659 | mas_pause(&mas); |
86039bd3 AA |
1660 | goto next; |
1661 | } | |
1662 | if (vma->vm_start < start) { | |
1663 | ret = split_vma(mm, vma, start, 1); | |
1664 | if (ret) | |
1665 | break; | |
59f2f4b8 | 1666 | mas_pause(&mas); |
86039bd3 AA |
1667 | } |
1668 | if (vma->vm_end > end) { | |
1669 | ret = split_vma(mm, vma, end, 0); | |
1670 | if (ret) | |
1671 | break; | |
59f2f4b8 | 1672 | mas_pause(&mas); |
86039bd3 AA |
1673 | } |
1674 | next: | |
1675 | /* | |
1676 | * In the vma_merge() successful mprotect-like case 8: | |
1677 | * the next vma was merged into the current one and | |
1678 | * the current one has not been updated yet. | |
1679 | */ | |
51d3d5eb | 1680 | userfaultfd_set_vm_flags(vma, new_flags); |
86039bd3 AA |
1681 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
1682 | ||
1683 | skip: | |
1684 | prev = vma; | |
1685 | start = vma->vm_end; | |
69dbe6da LH |
1686 | vma = mas_next(&mas, end - 1); |
1687 | } while (vma); | |
86039bd3 | 1688 | out_unlock: |
d8ed45c5 | 1689 | mmap_write_unlock(mm); |
d2005e3f | 1690 | mmput(mm); |
86039bd3 AA |
1691 | out: |
1692 | return ret; | |
1693 | } | |
1694 | ||
1695 | /* | |
ba85c702 AA |
1696 | * userfaultfd_wake may be used in combination with the |
1697 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. | |
86039bd3 AA |
1698 | */ |
1699 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, | |
1700 | unsigned long arg) | |
1701 | { | |
1702 | int ret; | |
1703 | struct uffdio_range uffdio_wake; | |
1704 | struct userfaultfd_wake_range range; | |
1705 | const void __user *buf = (void __user *)arg; | |
1706 | ||
1707 | ret = -EFAULT; | |
1708 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) | |
1709 | goto out; | |
1710 | ||
e71e2ace | 1711 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); |
86039bd3 AA |
1712 | if (ret) |
1713 | goto out; | |
1714 | ||
1715 | range.start = uffdio_wake.start; | |
1716 | range.len = uffdio_wake.len; | |
1717 | ||
1718 | /* | |
1719 | * len == 0 means wake all and we don't want to wake all here, | |
1720 | * so check it again to be sure. | |
1721 | */ | |
1722 | VM_BUG_ON(!range.len); | |
1723 | ||
1724 | wake_userfault(ctx, &range); | |
1725 | ret = 0; | |
1726 | ||
1727 | out: | |
1728 | return ret; | |
1729 | } | |
1730 | ||
ad465cae AA |
1731 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
1732 | unsigned long arg) | |
1733 | { | |
1734 | __s64 ret; | |
1735 | struct uffdio_copy uffdio_copy; | |
1736 | struct uffdio_copy __user *user_uffdio_copy; | |
1737 | struct userfaultfd_wake_range range; | |
1738 | ||
1739 | user_uffdio_copy = (struct uffdio_copy __user *) arg; | |
1740 | ||
df2cc96e | 1741 | ret = -EAGAIN; |
a759a909 | 1742 | if (atomic_read(&ctx->mmap_changing)) |
df2cc96e MR |
1743 | goto out; |
1744 | ||
ad465cae AA |
1745 | ret = -EFAULT; |
1746 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, | |
1747 | /* don't copy "copy" last field */ | |
1748 | sizeof(uffdio_copy)-sizeof(__s64))) | |
1749 | goto out; | |
1750 | ||
e71e2ace | 1751 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); |
ad465cae AA |
1752 | if (ret) |
1753 | goto out; | |
1754 | /* | |
1755 | * double check for wraparound just in case. copy_from_user() | |
1756 | * will later check uffdio_copy.src + uffdio_copy.len to fit | |
1757 | * in the userland range. | |
1758 | */ | |
1759 | ret = -EINVAL; | |
1760 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) | |
1761 | goto out; | |
72981e0e | 1762 | if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) |
ad465cae | 1763 | goto out; |
d2005e3f ON |
1764 | if (mmget_not_zero(ctx->mm)) { |
1765 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, | |
72981e0e AA |
1766 | uffdio_copy.len, &ctx->mmap_changing, |
1767 | uffdio_copy.mode); | |
d2005e3f | 1768 | mmput(ctx->mm); |
96333187 | 1769 | } else { |
e86b298b | 1770 | return -ESRCH; |
d2005e3f | 1771 | } |
ad465cae AA |
1772 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
1773 | return -EFAULT; | |
1774 | if (ret < 0) | |
1775 | goto out; | |
1776 | BUG_ON(!ret); | |
1777 | /* len == 0 would wake all */ | |
1778 | range.len = ret; | |
1779 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { | |
1780 | range.start = uffdio_copy.dst; | |
1781 | wake_userfault(ctx, &range); | |
1782 | } | |
1783 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; | |
1784 | out: | |
1785 | return ret; | |
1786 | } | |
1787 | ||
1788 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, | |
1789 | unsigned long arg) | |
1790 | { | |
1791 | __s64 ret; | |
1792 | struct uffdio_zeropage uffdio_zeropage; | |
1793 | struct uffdio_zeropage __user *user_uffdio_zeropage; | |
1794 | struct userfaultfd_wake_range range; | |
1795 | ||
1796 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; | |
1797 | ||
df2cc96e | 1798 | ret = -EAGAIN; |
a759a909 | 1799 | if (atomic_read(&ctx->mmap_changing)) |
df2cc96e MR |
1800 | goto out; |
1801 | ||
ad465cae AA |
1802 | ret = -EFAULT; |
1803 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, | |
1804 | /* don't copy "zeropage" last field */ | |
1805 | sizeof(uffdio_zeropage)-sizeof(__s64))) | |
1806 | goto out; | |
1807 | ||
e71e2ace | 1808 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, |
ad465cae AA |
1809 | uffdio_zeropage.range.len); |
1810 | if (ret) | |
1811 | goto out; | |
1812 | ret = -EINVAL; | |
1813 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) | |
1814 | goto out; | |
1815 | ||
d2005e3f ON |
1816 | if (mmget_not_zero(ctx->mm)) { |
1817 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, | |
df2cc96e MR |
1818 | uffdio_zeropage.range.len, |
1819 | &ctx->mmap_changing); | |
d2005e3f | 1820 | mmput(ctx->mm); |
9d95aa4b | 1821 | } else { |
e86b298b | 1822 | return -ESRCH; |
d2005e3f | 1823 | } |
ad465cae AA |
1824 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
1825 | return -EFAULT; | |
1826 | if (ret < 0) | |
1827 | goto out; | |
1828 | /* len == 0 would wake all */ | |
1829 | BUG_ON(!ret); | |
1830 | range.len = ret; | |
1831 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { | |
1832 | range.start = uffdio_zeropage.range.start; | |
1833 | wake_userfault(ctx, &range); | |
1834 | } | |
1835 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; | |
1836 | out: | |
1837 | return ret; | |
1838 | } | |
1839 | ||
63b2d417 AA |
1840 | static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, |
1841 | unsigned long arg) | |
1842 | { | |
1843 | int ret; | |
1844 | struct uffdio_writeprotect uffdio_wp; | |
1845 | struct uffdio_writeprotect __user *user_uffdio_wp; | |
1846 | struct userfaultfd_wake_range range; | |
23080e27 | 1847 | bool mode_wp, mode_dontwake; |
63b2d417 | 1848 | |
a759a909 | 1849 | if (atomic_read(&ctx->mmap_changing)) |
63b2d417 AA |
1850 | return -EAGAIN; |
1851 | ||
1852 | user_uffdio_wp = (struct uffdio_writeprotect __user *) arg; | |
1853 | ||
1854 | if (copy_from_user(&uffdio_wp, user_uffdio_wp, | |
1855 | sizeof(struct uffdio_writeprotect))) | |
1856 | return -EFAULT; | |
1857 | ||
e71e2ace | 1858 | ret = validate_range(ctx->mm, uffdio_wp.range.start, |
63b2d417 AA |
1859 | uffdio_wp.range.len); |
1860 | if (ret) | |
1861 | return ret; | |
1862 | ||
1863 | if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | | |
1864 | UFFDIO_WRITEPROTECT_MODE_WP)) | |
1865 | return -EINVAL; | |
23080e27 PX |
1866 | |
1867 | mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; | |
1868 | mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; | |
1869 | ||
1870 | if (mode_wp && mode_dontwake) | |
63b2d417 AA |
1871 | return -EINVAL; |
1872 | ||
cb185d5f NA |
1873 | if (mmget_not_zero(ctx->mm)) { |
1874 | ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, | |
1875 | uffdio_wp.range.len, mode_wp, | |
1876 | &ctx->mmap_changing); | |
1877 | mmput(ctx->mm); | |
1878 | } else { | |
1879 | return -ESRCH; | |
1880 | } | |
1881 | ||
63b2d417 AA |
1882 | if (ret) |
1883 | return ret; | |
1884 | ||
23080e27 | 1885 | if (!mode_wp && !mode_dontwake) { |
63b2d417 AA |
1886 | range.start = uffdio_wp.range.start; |
1887 | range.len = uffdio_wp.range.len; | |
1888 | wake_userfault(ctx, &range); | |
1889 | } | |
1890 | return ret; | |
1891 | } | |
1892 | ||
f6191471 AR |
1893 | static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) |
1894 | { | |
1895 | __s64 ret; | |
1896 | struct uffdio_continue uffdio_continue; | |
1897 | struct uffdio_continue __user *user_uffdio_continue; | |
1898 | struct userfaultfd_wake_range range; | |
1899 | ||
1900 | user_uffdio_continue = (struct uffdio_continue __user *)arg; | |
1901 | ||
1902 | ret = -EAGAIN; | |
a759a909 | 1903 | if (atomic_read(&ctx->mmap_changing)) |
f6191471 AR |
1904 | goto out; |
1905 | ||
1906 | ret = -EFAULT; | |
1907 | if (copy_from_user(&uffdio_continue, user_uffdio_continue, | |
1908 | /* don't copy the output fields */ | |
1909 | sizeof(uffdio_continue) - (sizeof(__s64)))) | |
1910 | goto out; | |
1911 | ||
e71e2ace | 1912 | ret = validate_range(ctx->mm, uffdio_continue.range.start, |
f6191471 AR |
1913 | uffdio_continue.range.len); |
1914 | if (ret) | |
1915 | goto out; | |
1916 | ||
1917 | ret = -EINVAL; | |
1918 | /* double check for wraparound just in case. */ | |
1919 | if (uffdio_continue.range.start + uffdio_continue.range.len <= | |
1920 | uffdio_continue.range.start) { | |
1921 | goto out; | |
1922 | } | |
1923 | if (uffdio_continue.mode & ~UFFDIO_CONTINUE_MODE_DONTWAKE) | |
1924 | goto out; | |
1925 | ||
1926 | if (mmget_not_zero(ctx->mm)) { | |
1927 | ret = mcopy_continue(ctx->mm, uffdio_continue.range.start, | |
1928 | uffdio_continue.range.len, | |
1929 | &ctx->mmap_changing); | |
1930 | mmput(ctx->mm); | |
1931 | } else { | |
1932 | return -ESRCH; | |
1933 | } | |
1934 | ||
1935 | if (unlikely(put_user(ret, &user_uffdio_continue->mapped))) | |
1936 | return -EFAULT; | |
1937 | if (ret < 0) | |
1938 | goto out; | |
1939 | ||
1940 | /* len == 0 would wake all */ | |
1941 | BUG_ON(!ret); | |
1942 | range.len = ret; | |
1943 | if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) { | |
1944 | range.start = uffdio_continue.range.start; | |
1945 | wake_userfault(ctx, &range); | |
1946 | } | |
1947 | ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN; | |
1948 | ||
1949 | out: | |
1950 | return ret; | |
1951 | } | |
1952 | ||
9cd75c3c PE |
1953 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
1954 | { | |
1955 | /* | |
22e5fe2a NA |
1956 | * For the current set of features the bits just coincide. Set |
1957 | * UFFD_FEATURE_INITIALIZED to mark the features as enabled. | |
9cd75c3c | 1958 | */ |
22e5fe2a | 1959 | return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; |
9cd75c3c PE |
1960 | } |
1961 | ||
86039bd3 AA |
1962 | /* |
1963 | * userland asks for a certain API version and we return which bits | |
1964 | * and ioctl commands are implemented in this kernel for such API | |
1965 | * version or -EINVAL if unknown. | |
1966 | */ | |
1967 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, | |
1968 | unsigned long arg) | |
1969 | { | |
1970 | struct uffdio_api uffdio_api; | |
1971 | void __user *buf = (void __user *)arg; | |
22e5fe2a | 1972 | unsigned int ctx_features; |
86039bd3 | 1973 | int ret; |
65603144 | 1974 | __u64 features; |
86039bd3 | 1975 | |
86039bd3 | 1976 | ret = -EFAULT; |
a9b85f94 | 1977 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
86039bd3 | 1978 | goto out; |
914eedcb AR |
1979 | /* Ignore unsupported features (userspace built against newer kernel) */ |
1980 | features = uffdio_api.features & UFFD_API_FEATURES; | |
3c1c24d9 MR |
1981 | ret = -EPERM; |
1982 | if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) | |
1983 | goto err_out; | |
65603144 AA |
1984 | /* report all available features and ioctls to userland */ |
1985 | uffdio_api.features = UFFD_API_FEATURES; | |
7677f7fd | 1986 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR |
964ab004 AR |
1987 | uffdio_api.features &= |
1988 | ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); | |
00b151f2 PX |
1989 | #endif |
1990 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP | |
1991 | uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; | |
b1f9e876 PX |
1992 | #endif |
1993 | #ifndef CONFIG_PTE_MARKER_UFFD_WP | |
1994 | uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM; | |
7677f7fd | 1995 | #endif |
86039bd3 AA |
1996 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
1997 | ret = -EFAULT; | |
1998 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1999 | goto out; | |
22e5fe2a | 2000 | |
65603144 | 2001 | /* only enable the requested features for this uffd context */ |
22e5fe2a NA |
2002 | ctx_features = uffd_ctx_features(features); |
2003 | ret = -EINVAL; | |
2004 | if (cmpxchg(&ctx->features, 0, ctx_features) != 0) | |
2005 | goto err_out; | |
2006 | ||
86039bd3 AA |
2007 | ret = 0; |
2008 | out: | |
2009 | return ret; | |
3c1c24d9 MR |
2010 | err_out: |
2011 | memset(&uffdio_api, 0, sizeof(uffdio_api)); | |
2012 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
2013 | ret = -EFAULT; | |
2014 | goto out; | |
86039bd3 AA |
2015 | } |
2016 | ||
2017 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, | |
2018 | unsigned long arg) | |
2019 | { | |
2020 | int ret = -EINVAL; | |
2021 | struct userfaultfd_ctx *ctx = file->private_data; | |
2022 | ||
22e5fe2a | 2023 | if (cmd != UFFDIO_API && !userfaultfd_is_initialized(ctx)) |
e6485a47 AA |
2024 | return -EINVAL; |
2025 | ||
86039bd3 AA |
2026 | switch(cmd) { |
2027 | case UFFDIO_API: | |
2028 | ret = userfaultfd_api(ctx, arg); | |
2029 | break; | |
2030 | case UFFDIO_REGISTER: | |
2031 | ret = userfaultfd_register(ctx, arg); | |
2032 | break; | |
2033 | case UFFDIO_UNREGISTER: | |
2034 | ret = userfaultfd_unregister(ctx, arg); | |
2035 | break; | |
2036 | case UFFDIO_WAKE: | |
2037 | ret = userfaultfd_wake(ctx, arg); | |
2038 | break; | |
ad465cae AA |
2039 | case UFFDIO_COPY: |
2040 | ret = userfaultfd_copy(ctx, arg); | |
2041 | break; | |
2042 | case UFFDIO_ZEROPAGE: | |
2043 | ret = userfaultfd_zeropage(ctx, arg); | |
2044 | break; | |
63b2d417 AA |
2045 | case UFFDIO_WRITEPROTECT: |
2046 | ret = userfaultfd_writeprotect(ctx, arg); | |
2047 | break; | |
f6191471 AR |
2048 | case UFFDIO_CONTINUE: |
2049 | ret = userfaultfd_continue(ctx, arg); | |
2050 | break; | |
86039bd3 AA |
2051 | } |
2052 | return ret; | |
2053 | } | |
2054 | ||
2055 | #ifdef CONFIG_PROC_FS | |
2056 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) | |
2057 | { | |
2058 | struct userfaultfd_ctx *ctx = f->private_data; | |
ac6424b9 | 2059 | wait_queue_entry_t *wq; |
86039bd3 AA |
2060 | unsigned long pending = 0, total = 0; |
2061 | ||
cbcfa130 | 2062 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
2055da97 | 2063 | list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { |
15b726ef AA |
2064 | pending++; |
2065 | total++; | |
2066 | } | |
2055da97 | 2067 | list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { |
86039bd3 AA |
2068 | total++; |
2069 | } | |
cbcfa130 | 2070 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
2071 | |
2072 | /* | |
2073 | * If more protocols will be added, there will be all shown | |
2074 | * separated by a space. Like this: | |
2075 | * protocols: aa:... bb:... | |
2076 | */ | |
2077 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", | |
045098e9 | 2078 | pending, total, UFFD_API, ctx->features, |
86039bd3 AA |
2079 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
2080 | } | |
2081 | #endif | |
2082 | ||
2083 | static const struct file_operations userfaultfd_fops = { | |
2084 | #ifdef CONFIG_PROC_FS | |
2085 | .show_fdinfo = userfaultfd_show_fdinfo, | |
2086 | #endif | |
2087 | .release = userfaultfd_release, | |
2088 | .poll = userfaultfd_poll, | |
2089 | .read = userfaultfd_read, | |
2090 | .unlocked_ioctl = userfaultfd_ioctl, | |
1832f2d8 | 2091 | .compat_ioctl = compat_ptr_ioctl, |
86039bd3 AA |
2092 | .llseek = noop_llseek, |
2093 | }; | |
2094 | ||
3004ec9c AA |
2095 | static void init_once_userfaultfd_ctx(void *mem) |
2096 | { | |
2097 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; | |
2098 | ||
2099 | init_waitqueue_head(&ctx->fault_pending_wqh); | |
2100 | init_waitqueue_head(&ctx->fault_wqh); | |
9cd75c3c | 2101 | init_waitqueue_head(&ctx->event_wqh); |
3004ec9c | 2102 | init_waitqueue_head(&ctx->fd_wqh); |
2ca97ac8 | 2103 | seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock); |
3004ec9c AA |
2104 | } |
2105 | ||
2d5de004 | 2106 | static int new_userfaultfd(int flags) |
86039bd3 | 2107 | { |
86039bd3 | 2108 | struct userfaultfd_ctx *ctx; |
284cd241 | 2109 | int fd; |
86039bd3 AA |
2110 | |
2111 | BUG_ON(!current->mm); | |
2112 | ||
2113 | /* Check the UFFD_* constants for consistency. */ | |
37cd0575 | 2114 | BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS); |
86039bd3 AA |
2115 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
2116 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); | |
2117 | ||
37cd0575 | 2118 | if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY)) |
284cd241 | 2119 | return -EINVAL; |
86039bd3 | 2120 | |
3004ec9c | 2121 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
86039bd3 | 2122 | if (!ctx) |
284cd241 | 2123 | return -ENOMEM; |
86039bd3 | 2124 | |
ca880420 | 2125 | refcount_set(&ctx->refcount, 1); |
86039bd3 | 2126 | ctx->flags = flags; |
9cd75c3c | 2127 | ctx->features = 0; |
86039bd3 | 2128 | ctx->released = false; |
a759a909 | 2129 | atomic_set(&ctx->mmap_changing, 0); |
86039bd3 AA |
2130 | ctx->mm = current->mm; |
2131 | /* prevent the mm struct to be freed */ | |
f1f10076 | 2132 | mmgrab(ctx->mm); |
86039bd3 | 2133 | |
b537900f | 2134 | fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx, |
abec3d01 | 2135 | O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); |
284cd241 | 2136 | if (fd < 0) { |
d2005e3f | 2137 | mmdrop(ctx->mm); |
3004ec9c | 2138 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
c03e946f | 2139 | } |
86039bd3 | 2140 | return fd; |
86039bd3 | 2141 | } |
3004ec9c | 2142 | |
2d5de004 AR |
2143 | static inline bool userfaultfd_syscall_allowed(int flags) |
2144 | { | |
2145 | /* Userspace-only page faults are always allowed */ | |
2146 | if (flags & UFFD_USER_MODE_ONLY) | |
2147 | return true; | |
2148 | ||
2149 | /* | |
2150 | * The user is requesting a userfaultfd which can handle kernel faults. | |
2151 | * Privileged users are always allowed to do this. | |
2152 | */ | |
2153 | if (capable(CAP_SYS_PTRACE)) | |
2154 | return true; | |
2155 | ||
2156 | /* Otherwise, access to kernel fault handling is sysctl controlled. */ | |
2157 | return sysctl_unprivileged_userfaultfd; | |
2158 | } | |
2159 | ||
2160 | SYSCALL_DEFINE1(userfaultfd, int, flags) | |
2161 | { | |
2162 | if (!userfaultfd_syscall_allowed(flags)) | |
2163 | return -EPERM; | |
2164 | ||
2165 | return new_userfaultfd(flags); | |
2166 | } | |
2167 | ||
2168 | static long userfaultfd_dev_ioctl(struct file *file, unsigned int cmd, unsigned long flags) | |
2169 | { | |
2170 | if (cmd != USERFAULTFD_IOC_NEW) | |
2171 | return -EINVAL; | |
2172 | ||
2173 | return new_userfaultfd(flags); | |
2174 | } | |
2175 | ||
2176 | static const struct file_operations userfaultfd_dev_fops = { | |
2177 | .unlocked_ioctl = userfaultfd_dev_ioctl, | |
2178 | .compat_ioctl = userfaultfd_dev_ioctl, | |
2179 | .owner = THIS_MODULE, | |
2180 | .llseek = noop_llseek, | |
2181 | }; | |
2182 | ||
2183 | static struct miscdevice userfaultfd_misc = { | |
2184 | .minor = MISC_DYNAMIC_MINOR, | |
2185 | .name = "userfaultfd", | |
2186 | .fops = &userfaultfd_dev_fops | |
2187 | }; | |
2188 | ||
3004ec9c AA |
2189 | static int __init userfaultfd_init(void) |
2190 | { | |
2d5de004 AR |
2191 | int ret; |
2192 | ||
2193 | ret = misc_register(&userfaultfd_misc); | |
2194 | if (ret) | |
2195 | return ret; | |
2196 | ||
3004ec9c AA |
2197 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", |
2198 | sizeof(struct userfaultfd_ctx), | |
2199 | 0, | |
2200 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, | |
2201 | init_once_userfaultfd_ctx); | |
2202 | return 0; | |
2203 | } | |
2204 | __initcall(userfaultfd_init); |