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