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> |
86039bd3 | 32 | |
d0d4730a | 33 | int sysctl_unprivileged_userfaultfd __read_mostly; |
cefdca0a | 34 | |
3004ec9c AA |
35 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
36 | ||
3004ec9c AA |
37 | /* |
38 | * Start with fault_pending_wqh and fault_wqh so they're more likely | |
39 | * to be in the same cacheline. | |
cbcfa130 EB |
40 | * |
41 | * Locking order: | |
42 | * fd_wqh.lock | |
43 | * fault_pending_wqh.lock | |
44 | * fault_wqh.lock | |
45 | * event_wqh.lock | |
46 | * | |
47 | * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, | |
48 | * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's | |
49 | * also taken in IRQ context. | |
3004ec9c | 50 | */ |
86039bd3 | 51 | struct userfaultfd_ctx { |
15b726ef AA |
52 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
53 | wait_queue_head_t fault_pending_wqh; | |
54 | /* waitqueue head for the userfaults */ | |
86039bd3 AA |
55 | wait_queue_head_t fault_wqh; |
56 | /* waitqueue head for the pseudo fd to wakeup poll/read */ | |
57 | wait_queue_head_t fd_wqh; | |
9cd75c3c PE |
58 | /* waitqueue head for events */ |
59 | wait_queue_head_t event_wqh; | |
2c5b7e1b | 60 | /* a refile sequence protected by fault_pending_wqh lock */ |
2ca97ac8 | 61 | seqcount_spinlock_t refile_seq; |
3004ec9c | 62 | /* pseudo fd refcounting */ |
ca880420 | 63 | refcount_t refcount; |
86039bd3 AA |
64 | /* userfaultfd syscall flags */ |
65 | unsigned int flags; | |
9cd75c3c PE |
66 | /* features requested from the userspace */ |
67 | unsigned int features; | |
86039bd3 AA |
68 | /* released */ |
69 | bool released; | |
df2cc96e | 70 | /* memory mappings are changing because of non-cooperative event */ |
a759a909 | 71 | atomic_t mmap_changing; |
86039bd3 AA |
72 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ |
73 | struct mm_struct *mm; | |
74 | }; | |
75 | ||
893e26e6 PE |
76 | struct userfaultfd_fork_ctx { |
77 | struct userfaultfd_ctx *orig; | |
78 | struct userfaultfd_ctx *new; | |
79 | struct list_head list; | |
80 | }; | |
81 | ||
897ab3e0 MR |
82 | struct userfaultfd_unmap_ctx { |
83 | struct userfaultfd_ctx *ctx; | |
84 | unsigned long start; | |
85 | unsigned long end; | |
86 | struct list_head list; | |
87 | }; | |
88 | ||
86039bd3 | 89 | struct userfaultfd_wait_queue { |
a9b85f94 | 90 | struct uffd_msg msg; |
ac6424b9 | 91 | wait_queue_entry_t wq; |
86039bd3 | 92 | struct userfaultfd_ctx *ctx; |
15a77c6f | 93 | bool waken; |
86039bd3 AA |
94 | }; |
95 | ||
96 | struct userfaultfd_wake_range { | |
97 | unsigned long start; | |
98 | unsigned long len; | |
99 | }; | |
100 | ||
22e5fe2a NA |
101 | /* internal indication that UFFD_API ioctl was successfully executed */ |
102 | #define UFFD_FEATURE_INITIALIZED (1u << 31) | |
103 | ||
104 | static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx) | |
105 | { | |
106 | return ctx->features & UFFD_FEATURE_INITIALIZED; | |
107 | } | |
108 | ||
ac6424b9 | 109 | static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, |
86039bd3 AA |
110 | int wake_flags, void *key) |
111 | { | |
112 | struct userfaultfd_wake_range *range = key; | |
113 | int ret; | |
114 | struct userfaultfd_wait_queue *uwq; | |
115 | unsigned long start, len; | |
116 | ||
117 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
118 | ret = 0; | |
86039bd3 AA |
119 | /* len == 0 means wake all */ |
120 | start = range->start; | |
121 | len = range->len; | |
a9b85f94 AA |
122 | if (len && (start > uwq->msg.arg.pagefault.address || |
123 | start + len <= uwq->msg.arg.pagefault.address)) | |
86039bd3 | 124 | goto out; |
15a77c6f AA |
125 | WRITE_ONCE(uwq->waken, true); |
126 | /* | |
a9668cd6 PZ |
127 | * The Program-Order guarantees provided by the scheduler |
128 | * ensure uwq->waken is visible before the task is woken. | |
15a77c6f | 129 | */ |
86039bd3 | 130 | ret = wake_up_state(wq->private, mode); |
a9668cd6 | 131 | if (ret) { |
86039bd3 AA |
132 | /* |
133 | * Wake only once, autoremove behavior. | |
134 | * | |
a9668cd6 PZ |
135 | * After the effect of list_del_init is visible to the other |
136 | * CPUs, the waitqueue may disappear from under us, see the | |
137 | * !list_empty_careful() in handle_userfault(). | |
138 | * | |
139 | * try_to_wake_up() has an implicit smp_mb(), and the | |
140 | * wq->private is read before calling the extern function | |
141 | * "wake_up_state" (which in turns calls try_to_wake_up). | |
86039bd3 | 142 | */ |
2055da97 | 143 | list_del_init(&wq->entry); |
a9668cd6 | 144 | } |
86039bd3 AA |
145 | out: |
146 | return ret; | |
147 | } | |
148 | ||
149 | /** | |
150 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd | |
151 | * context. | |
152 | * @ctx: [in] Pointer to the userfaultfd context. | |
86039bd3 AA |
153 | */ |
154 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) | |
155 | { | |
ca880420 | 156 | refcount_inc(&ctx->refcount); |
86039bd3 AA |
157 | } |
158 | ||
159 | /** | |
160 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd | |
161 | * context. | |
162 | * @ctx: [in] Pointer to userfaultfd context. | |
163 | * | |
164 | * The userfaultfd context reference must have been previously acquired either | |
165 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). | |
166 | */ | |
167 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) | |
168 | { | |
ca880420 | 169 | if (refcount_dec_and_test(&ctx->refcount)) { |
86039bd3 AA |
170 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); |
171 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); | |
172 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); | |
173 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); | |
9cd75c3c PE |
174 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
175 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); | |
86039bd3 AA |
176 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
177 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); | |
d2005e3f | 178 | mmdrop(ctx->mm); |
3004ec9c | 179 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
86039bd3 AA |
180 | } |
181 | } | |
182 | ||
a9b85f94 | 183 | static inline void msg_init(struct uffd_msg *msg) |
86039bd3 | 184 | { |
a9b85f94 AA |
185 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
186 | /* | |
187 | * Must use memset to zero out the paddings or kernel data is | |
188 | * leaked to userland. | |
189 | */ | |
190 | memset(msg, 0, sizeof(struct uffd_msg)); | |
191 | } | |
192 | ||
193 | static inline struct uffd_msg userfault_msg(unsigned long address, | |
194 | unsigned int flags, | |
9d4ac934 AP |
195 | unsigned long reason, |
196 | unsigned int features) | |
a9b85f94 AA |
197 | { |
198 | struct uffd_msg msg; | |
199 | msg_init(&msg); | |
200 | msg.event = UFFD_EVENT_PAGEFAULT; | |
201 | msg.arg.pagefault.address = address; | |
7677f7fd AR |
202 | /* |
203 | * These flags indicate why the userfault occurred: | |
204 | * - UFFD_PAGEFAULT_FLAG_WP indicates a write protect fault. | |
205 | * - UFFD_PAGEFAULT_FLAG_MINOR indicates a minor fault. | |
206 | * - Neither of these flags being set indicates a MISSING fault. | |
207 | * | |
208 | * Separately, UFFD_PAGEFAULT_FLAG_WRITE indicates it was a write | |
209 | * fault. Otherwise, it was a read fault. | |
210 | */ | |
86039bd3 | 211 | if (flags & FAULT_FLAG_WRITE) |
a9b85f94 | 212 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
86039bd3 | 213 | if (reason & VM_UFFD_WP) |
a9b85f94 | 214 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
7677f7fd AR |
215 | if (reason & VM_UFFD_MINOR) |
216 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_MINOR; | |
9d4ac934 | 217 | if (features & UFFD_FEATURE_THREAD_ID) |
a36985d3 | 218 | msg.arg.pagefault.feat.ptid = task_pid_vnr(current); |
a9b85f94 | 219 | return msg; |
86039bd3 AA |
220 | } |
221 | ||
369cd212 MK |
222 | #ifdef CONFIG_HUGETLB_PAGE |
223 | /* | |
224 | * Same functionality as userfaultfd_must_wait below with modifications for | |
225 | * hugepmd ranges. | |
226 | */ | |
227 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 228 | struct vm_area_struct *vma, |
369cd212 MK |
229 | unsigned long address, |
230 | unsigned long flags, | |
231 | unsigned long reason) | |
232 | { | |
233 | struct mm_struct *mm = ctx->mm; | |
1e2c0436 | 234 | pte_t *ptep, pte; |
369cd212 MK |
235 | bool ret = true; |
236 | ||
42fc5414 | 237 | mmap_assert_locked(mm); |
369cd212 | 238 | |
1e2c0436 JF |
239 | ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma)); |
240 | ||
241 | if (!ptep) | |
369cd212 MK |
242 | goto out; |
243 | ||
244 | ret = false; | |
1e2c0436 | 245 | pte = huge_ptep_get(ptep); |
369cd212 MK |
246 | |
247 | /* | |
248 | * Lockless access: we're in a wait_event so it's ok if it | |
249 | * changes under us. | |
250 | */ | |
1e2c0436 | 251 | if (huge_pte_none(pte)) |
369cd212 | 252 | ret = true; |
1e2c0436 | 253 | if (!huge_pte_write(pte) && (reason & VM_UFFD_WP)) |
369cd212 MK |
254 | ret = true; |
255 | out: | |
256 | return ret; | |
257 | } | |
258 | #else | |
259 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 260 | struct vm_area_struct *vma, |
369cd212 MK |
261 | unsigned long address, |
262 | unsigned long flags, | |
263 | unsigned long reason) | |
264 | { | |
265 | return false; /* should never get here */ | |
266 | } | |
267 | #endif /* CONFIG_HUGETLB_PAGE */ | |
268 | ||
8d2afd96 AA |
269 | /* |
270 | * Verify the pagetables are still not ok after having reigstered into | |
271 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any | |
272 | * userfault that has already been resolved, if userfaultfd_read and | |
273 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different | |
274 | * threads. | |
275 | */ | |
276 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, | |
277 | unsigned long address, | |
278 | unsigned long flags, | |
279 | unsigned long reason) | |
280 | { | |
281 | struct mm_struct *mm = ctx->mm; | |
282 | pgd_t *pgd; | |
c2febafc | 283 | p4d_t *p4d; |
8d2afd96 AA |
284 | pud_t *pud; |
285 | pmd_t *pmd, _pmd; | |
286 | pte_t *pte; | |
287 | bool ret = true; | |
288 | ||
42fc5414 | 289 | mmap_assert_locked(mm); |
8d2afd96 AA |
290 | |
291 | pgd = pgd_offset(mm, address); | |
292 | if (!pgd_present(*pgd)) | |
293 | goto out; | |
c2febafc KS |
294 | p4d = p4d_offset(pgd, address); |
295 | if (!p4d_present(*p4d)) | |
296 | goto out; | |
297 | pud = pud_offset(p4d, address); | |
8d2afd96 AA |
298 | if (!pud_present(*pud)) |
299 | goto out; | |
300 | pmd = pmd_offset(pud, address); | |
301 | /* | |
302 | * READ_ONCE must function as a barrier with narrower scope | |
303 | * and it must be equivalent to: | |
304 | * _pmd = *pmd; barrier(); | |
305 | * | |
306 | * This is to deal with the instability (as in | |
307 | * pmd_trans_unstable) of the pmd. | |
308 | */ | |
309 | _pmd = READ_ONCE(*pmd); | |
a365ac09 | 310 | if (pmd_none(_pmd)) |
8d2afd96 AA |
311 | goto out; |
312 | ||
313 | ret = false; | |
a365ac09 HY |
314 | if (!pmd_present(_pmd)) |
315 | goto out; | |
316 | ||
63b2d417 AA |
317 | if (pmd_trans_huge(_pmd)) { |
318 | if (!pmd_write(_pmd) && (reason & VM_UFFD_WP)) | |
319 | ret = true; | |
8d2afd96 | 320 | goto out; |
63b2d417 | 321 | } |
8d2afd96 AA |
322 | |
323 | /* | |
324 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it | |
325 | * and use the standard pte_offset_map() instead of parsing _pmd. | |
326 | */ | |
327 | pte = pte_offset_map(pmd, address); | |
328 | /* | |
329 | * Lockless access: we're in a wait_event so it's ok if it | |
330 | * changes under us. | |
331 | */ | |
332 | if (pte_none(*pte)) | |
333 | ret = true; | |
63b2d417 AA |
334 | if (!pte_write(*pte) && (reason & VM_UFFD_WP)) |
335 | ret = true; | |
8d2afd96 AA |
336 | pte_unmap(pte); |
337 | ||
338 | out: | |
339 | return ret; | |
340 | } | |
341 | ||
2f064a59 | 342 | static inline unsigned int userfaultfd_get_blocking_state(unsigned int flags) |
3e69ad08 PX |
343 | { |
344 | if (flags & FAULT_FLAG_INTERRUPTIBLE) | |
345 | return TASK_INTERRUPTIBLE; | |
346 | ||
347 | if (flags & FAULT_FLAG_KILLABLE) | |
348 | return TASK_KILLABLE; | |
349 | ||
350 | return TASK_UNINTERRUPTIBLE; | |
351 | } | |
352 | ||
86039bd3 AA |
353 | /* |
354 | * The locking rules involved in returning VM_FAULT_RETRY depending on | |
355 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and | |
356 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" | |
357 | * recommendation in __lock_page_or_retry is not an understatement. | |
358 | * | |
c1e8d7c6 | 359 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_lock must be released |
86039bd3 AA |
360 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is |
361 | * not set. | |
362 | * | |
363 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not | |
364 | * set, VM_FAULT_RETRY can still be returned if and only if there are | |
c1e8d7c6 | 365 | * fatal_signal_pending()s, and the mmap_lock must be released before |
86039bd3 AA |
366 | * returning it. |
367 | */ | |
2b740303 | 368 | vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) |
86039bd3 | 369 | { |
82b0f8c3 | 370 | struct mm_struct *mm = vmf->vma->vm_mm; |
86039bd3 AA |
371 | struct userfaultfd_ctx *ctx; |
372 | struct userfaultfd_wait_queue uwq; | |
2b740303 | 373 | vm_fault_t ret = VM_FAULT_SIGBUS; |
3e69ad08 | 374 | bool must_wait; |
2f064a59 | 375 | unsigned int blocking_state; |
86039bd3 | 376 | |
64c2b203 AA |
377 | /* |
378 | * We don't do userfault handling for the final child pid update. | |
379 | * | |
380 | * We also don't do userfault handling during | |
381 | * coredumping. hugetlbfs has the special | |
382 | * follow_hugetlb_page() to skip missing pages in the | |
383 | * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with | |
384 | * the no_page_table() helper in follow_page_mask(), but the | |
385 | * shmem_vm_ops->fault method is invoked even during | |
c1e8d7c6 | 386 | * coredumping without mmap_lock and it ends up here. |
64c2b203 AA |
387 | */ |
388 | if (current->flags & (PF_EXITING|PF_DUMPCORE)) | |
389 | goto out; | |
390 | ||
391 | /* | |
c1e8d7c6 ML |
392 | * Coredumping runs without mmap_lock so we can only check that |
393 | * the mmap_lock is held, if PF_DUMPCORE was not set. | |
64c2b203 | 394 | */ |
42fc5414 | 395 | mmap_assert_locked(mm); |
64c2b203 | 396 | |
82b0f8c3 | 397 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
86039bd3 | 398 | if (!ctx) |
ba85c702 | 399 | goto out; |
86039bd3 AA |
400 | |
401 | BUG_ON(ctx->mm != mm); | |
402 | ||
7677f7fd AR |
403 | /* Any unrecognized flag is a bug. */ |
404 | VM_BUG_ON(reason & ~__VM_UFFD_FLAGS); | |
405 | /* 0 or > 1 flags set is a bug; we expect exactly 1. */ | |
406 | VM_BUG_ON(!reason || (reason & (reason - 1))); | |
86039bd3 | 407 | |
2d6d6f5a PS |
408 | if (ctx->features & UFFD_FEATURE_SIGBUS) |
409 | goto out; | |
37cd0575 LG |
410 | if ((vmf->flags & FAULT_FLAG_USER) == 0 && |
411 | ctx->flags & UFFD_USER_MODE_ONLY) { | |
412 | printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd " | |
413 | "sysctl knob to 1 if kernel faults must be handled " | |
414 | "without obtaining CAP_SYS_PTRACE capability\n"); | |
415 | goto out; | |
416 | } | |
2d6d6f5a | 417 | |
86039bd3 AA |
418 | /* |
419 | * If it's already released don't get it. This avoids to loop | |
420 | * in __get_user_pages if userfaultfd_release waits on the | |
c1e8d7c6 | 421 | * caller of handle_userfault to release the mmap_lock. |
86039bd3 | 422 | */ |
6aa7de05 | 423 | if (unlikely(READ_ONCE(ctx->released))) { |
656710a6 AA |
424 | /* |
425 | * Don't return VM_FAULT_SIGBUS in this case, so a non | |
426 | * cooperative manager can close the uffd after the | |
427 | * last UFFDIO_COPY, without risking to trigger an | |
428 | * involuntary SIGBUS if the process was starting the | |
429 | * userfaultfd while the userfaultfd was still armed | |
430 | * (but after the last UFFDIO_COPY). If the uffd | |
431 | * wasn't already closed when the userfault reached | |
432 | * this point, that would normally be solved by | |
433 | * userfaultfd_must_wait returning 'false'. | |
434 | * | |
435 | * If we were to return VM_FAULT_SIGBUS here, the non | |
436 | * cooperative manager would be instead forced to | |
437 | * always call UFFDIO_UNREGISTER before it can safely | |
438 | * close the uffd. | |
439 | */ | |
440 | ret = VM_FAULT_NOPAGE; | |
ba85c702 | 441 | goto out; |
656710a6 | 442 | } |
86039bd3 AA |
443 | |
444 | /* | |
445 | * Check that we can return VM_FAULT_RETRY. | |
446 | * | |
447 | * NOTE: it should become possible to return VM_FAULT_RETRY | |
448 | * even if FAULT_FLAG_TRIED is set without leading to gup() | |
449 | * -EBUSY failures, if the userfaultfd is to be extended for | |
450 | * VM_UFFD_WP tracking and we intend to arm the userfault | |
451 | * without first stopping userland access to the memory. For | |
452 | * VM_UFFD_MISSING userfaults this is enough for now. | |
453 | */ | |
82b0f8c3 | 454 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
86039bd3 AA |
455 | /* |
456 | * Validate the invariant that nowait must allow retry | |
457 | * to be sure not to return SIGBUS erroneously on | |
458 | * nowait invocations. | |
459 | */ | |
82b0f8c3 | 460 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
86039bd3 AA |
461 | #ifdef CONFIG_DEBUG_VM |
462 | if (printk_ratelimit()) { | |
463 | printk(KERN_WARNING | |
82b0f8c3 JK |
464 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
465 | vmf->flags); | |
86039bd3 AA |
466 | dump_stack(); |
467 | } | |
468 | #endif | |
ba85c702 | 469 | goto out; |
86039bd3 AA |
470 | } |
471 | ||
472 | /* | |
473 | * Handle nowait, not much to do other than tell it to retry | |
474 | * and wait. | |
475 | */ | |
ba85c702 | 476 | ret = VM_FAULT_RETRY; |
82b0f8c3 | 477 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
ba85c702 | 478 | goto out; |
86039bd3 | 479 | |
c1e8d7c6 | 480 | /* take the reference before dropping the mmap_lock */ |
86039bd3 AA |
481 | userfaultfd_ctx_get(ctx); |
482 | ||
86039bd3 AA |
483 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
484 | uwq.wq.private = current; | |
9d4ac934 AP |
485 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason, |
486 | ctx->features); | |
86039bd3 | 487 | uwq.ctx = ctx; |
15a77c6f | 488 | uwq.waken = false; |
86039bd3 | 489 | |
3e69ad08 | 490 | blocking_state = userfaultfd_get_blocking_state(vmf->flags); |
dfa37dc3 | 491 | |
cbcfa130 | 492 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
493 | /* |
494 | * After the __add_wait_queue the uwq is visible to userland | |
495 | * through poll/read(). | |
496 | */ | |
15b726ef AA |
497 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
498 | /* | |
499 | * The smp_mb() after __set_current_state prevents the reads | |
500 | * following the spin_unlock to happen before the list_add in | |
501 | * __add_wait_queue. | |
502 | */ | |
15a77c6f | 503 | set_current_state(blocking_state); |
cbcfa130 | 504 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 505 | |
369cd212 MK |
506 | if (!is_vm_hugetlb_page(vmf->vma)) |
507 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, | |
508 | reason); | |
509 | else | |
7868a208 PA |
510 | must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma, |
511 | vmf->address, | |
369cd212 | 512 | vmf->flags, reason); |
d8ed45c5 | 513 | mmap_read_unlock(mm); |
8d2afd96 | 514 | |
f9bf3522 | 515 | if (likely(must_wait && !READ_ONCE(ctx->released))) { |
a9a08845 | 516 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
86039bd3 | 517 | schedule(); |
ba85c702 | 518 | } |
86039bd3 | 519 | |
ba85c702 | 520 | __set_current_state(TASK_RUNNING); |
15b726ef AA |
521 | |
522 | /* | |
523 | * Here we race with the list_del; list_add in | |
524 | * userfaultfd_ctx_read(), however because we don't ever run | |
525 | * list_del_init() to refile across the two lists, the prev | |
526 | * and next pointers will never point to self. list_add also | |
527 | * would never let any of the two pointers to point to | |
528 | * self. So list_empty_careful won't risk to see both pointers | |
529 | * pointing to self at any time during the list refile. The | |
530 | * only case where list_del_init() is called is the full | |
531 | * removal in the wake function and there we don't re-list_add | |
532 | * and it's fine not to block on the spinlock. The uwq on this | |
533 | * kernel stack can be released after the list_del_init. | |
534 | */ | |
2055da97 | 535 | if (!list_empty_careful(&uwq.wq.entry)) { |
cbcfa130 | 536 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
15b726ef AA |
537 | /* |
538 | * No need of list_del_init(), the uwq on the stack | |
539 | * will be freed shortly anyway. | |
540 | */ | |
2055da97 | 541 | list_del(&uwq.wq.entry); |
cbcfa130 | 542 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 543 | } |
86039bd3 AA |
544 | |
545 | /* | |
546 | * ctx may go away after this if the userfault pseudo fd is | |
547 | * already released. | |
548 | */ | |
549 | userfaultfd_ctx_put(ctx); | |
550 | ||
ba85c702 AA |
551 | out: |
552 | return ret; | |
86039bd3 AA |
553 | } |
554 | ||
8c9e7bb7 AA |
555 | static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
556 | struct userfaultfd_wait_queue *ewq) | |
9cd75c3c | 557 | { |
0cbb4b4f AA |
558 | struct userfaultfd_ctx *release_new_ctx; |
559 | ||
9a69a829 AA |
560 | if (WARN_ON_ONCE(current->flags & PF_EXITING)) |
561 | goto out; | |
9cd75c3c PE |
562 | |
563 | ewq->ctx = ctx; | |
564 | init_waitqueue_entry(&ewq->wq, current); | |
0cbb4b4f | 565 | release_new_ctx = NULL; |
9cd75c3c | 566 | |
cbcfa130 | 567 | spin_lock_irq(&ctx->event_wqh.lock); |
9cd75c3c PE |
568 | /* |
569 | * After the __add_wait_queue the uwq is visible to userland | |
570 | * through poll/read(). | |
571 | */ | |
572 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); | |
573 | for (;;) { | |
574 | set_current_state(TASK_KILLABLE); | |
575 | if (ewq->msg.event == 0) | |
576 | break; | |
6aa7de05 | 577 | if (READ_ONCE(ctx->released) || |
9cd75c3c | 578 | fatal_signal_pending(current)) { |
384632e6 AA |
579 | /* |
580 | * &ewq->wq may be queued in fork_event, but | |
581 | * __remove_wait_queue ignores the head | |
582 | * parameter. It would be a problem if it | |
583 | * didn't. | |
584 | */ | |
9cd75c3c | 585 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
7eb76d45 MR |
586 | if (ewq->msg.event == UFFD_EVENT_FORK) { |
587 | struct userfaultfd_ctx *new; | |
588 | ||
589 | new = (struct userfaultfd_ctx *) | |
590 | (unsigned long) | |
591 | ewq->msg.arg.reserved.reserved1; | |
0cbb4b4f | 592 | release_new_ctx = new; |
7eb76d45 | 593 | } |
9cd75c3c PE |
594 | break; |
595 | } | |
596 | ||
cbcfa130 | 597 | spin_unlock_irq(&ctx->event_wqh.lock); |
9cd75c3c | 598 | |
a9a08845 | 599 | wake_up_poll(&ctx->fd_wqh, EPOLLIN); |
9cd75c3c PE |
600 | schedule(); |
601 | ||
cbcfa130 | 602 | spin_lock_irq(&ctx->event_wqh.lock); |
9cd75c3c PE |
603 | } |
604 | __set_current_state(TASK_RUNNING); | |
cbcfa130 | 605 | spin_unlock_irq(&ctx->event_wqh.lock); |
9cd75c3c | 606 | |
0cbb4b4f AA |
607 | if (release_new_ctx) { |
608 | struct vm_area_struct *vma; | |
609 | struct mm_struct *mm = release_new_ctx->mm; | |
610 | ||
611 | /* the various vma->vm_userfaultfd_ctx still points to it */ | |
d8ed45c5 | 612 | mmap_write_lock(mm); |
0cbb4b4f | 613 | for (vma = mm->mmap; vma; vma = vma->vm_next) |
31e810aa | 614 | if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) { |
0cbb4b4f | 615 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; |
7677f7fd | 616 | vma->vm_flags &= ~__VM_UFFD_FLAGS; |
31e810aa | 617 | } |
d8ed45c5 | 618 | mmap_write_unlock(mm); |
0cbb4b4f AA |
619 | |
620 | userfaultfd_ctx_put(release_new_ctx); | |
621 | } | |
622 | ||
9cd75c3c PE |
623 | /* |
624 | * ctx may go away after this if the userfault pseudo fd is | |
625 | * already released. | |
626 | */ | |
9a69a829 | 627 | out: |
a759a909 NA |
628 | atomic_dec(&ctx->mmap_changing); |
629 | VM_BUG_ON(atomic_read(&ctx->mmap_changing) < 0); | |
9cd75c3c | 630 | userfaultfd_ctx_put(ctx); |
9cd75c3c PE |
631 | } |
632 | ||
633 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, | |
634 | struct userfaultfd_wait_queue *ewq) | |
635 | { | |
636 | ewq->msg.event = 0; | |
637 | wake_up_locked(&ctx->event_wqh); | |
638 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
639 | } | |
640 | ||
893e26e6 PE |
641 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
642 | { | |
643 | struct userfaultfd_ctx *ctx = NULL, *octx; | |
644 | struct userfaultfd_fork_ctx *fctx; | |
645 | ||
646 | octx = vma->vm_userfaultfd_ctx.ctx; | |
647 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { | |
648 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
7677f7fd | 649 | vma->vm_flags &= ~__VM_UFFD_FLAGS; |
893e26e6 PE |
650 | return 0; |
651 | } | |
652 | ||
653 | list_for_each_entry(fctx, fcs, list) | |
654 | if (fctx->orig == octx) { | |
655 | ctx = fctx->new; | |
656 | break; | |
657 | } | |
658 | ||
659 | if (!ctx) { | |
660 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); | |
661 | if (!fctx) | |
662 | return -ENOMEM; | |
663 | ||
664 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); | |
665 | if (!ctx) { | |
666 | kfree(fctx); | |
667 | return -ENOMEM; | |
668 | } | |
669 | ||
ca880420 | 670 | refcount_set(&ctx->refcount, 1); |
893e26e6 | 671 | ctx->flags = octx->flags; |
893e26e6 PE |
672 | ctx->features = octx->features; |
673 | ctx->released = false; | |
a759a909 | 674 | atomic_set(&ctx->mmap_changing, 0); |
893e26e6 | 675 | ctx->mm = vma->vm_mm; |
00bb31fa | 676 | mmgrab(ctx->mm); |
893e26e6 PE |
677 | |
678 | userfaultfd_ctx_get(octx); | |
a759a909 | 679 | atomic_inc(&octx->mmap_changing); |
893e26e6 PE |
680 | fctx->orig = octx; |
681 | fctx->new = ctx; | |
682 | list_add_tail(&fctx->list, fcs); | |
683 | } | |
684 | ||
685 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
686 | return 0; | |
687 | } | |
688 | ||
8c9e7bb7 | 689 | static void dup_fctx(struct userfaultfd_fork_ctx *fctx) |
893e26e6 PE |
690 | { |
691 | struct userfaultfd_ctx *ctx = fctx->orig; | |
692 | struct userfaultfd_wait_queue ewq; | |
693 | ||
694 | msg_init(&ewq.msg); | |
695 | ||
696 | ewq.msg.event = UFFD_EVENT_FORK; | |
697 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; | |
698 | ||
8c9e7bb7 | 699 | userfaultfd_event_wait_completion(ctx, &ewq); |
893e26e6 PE |
700 | } |
701 | ||
702 | void dup_userfaultfd_complete(struct list_head *fcs) | |
703 | { | |
893e26e6 PE |
704 | struct userfaultfd_fork_ctx *fctx, *n; |
705 | ||
706 | list_for_each_entry_safe(fctx, n, fcs, list) { | |
8c9e7bb7 | 707 | dup_fctx(fctx); |
893e26e6 PE |
708 | list_del(&fctx->list); |
709 | kfree(fctx); | |
710 | } | |
711 | } | |
712 | ||
72f87654 PE |
713 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
714 | struct vm_userfaultfd_ctx *vm_ctx) | |
715 | { | |
716 | struct userfaultfd_ctx *ctx; | |
717 | ||
718 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
3cfd22be PX |
719 | |
720 | if (!ctx) | |
721 | return; | |
722 | ||
723 | if (ctx->features & UFFD_FEATURE_EVENT_REMAP) { | |
72f87654 PE |
724 | vm_ctx->ctx = ctx; |
725 | userfaultfd_ctx_get(ctx); | |
a759a909 | 726 | atomic_inc(&ctx->mmap_changing); |
3cfd22be PX |
727 | } else { |
728 | /* Drop uffd context if remap feature not enabled */ | |
729 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
7677f7fd | 730 | vma->vm_flags &= ~__VM_UFFD_FLAGS; |
72f87654 PE |
731 | } |
732 | } | |
733 | ||
90794bf1 | 734 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
72f87654 PE |
735 | unsigned long from, unsigned long to, |
736 | unsigned long len) | |
737 | { | |
90794bf1 | 738 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
72f87654 PE |
739 | struct userfaultfd_wait_queue ewq; |
740 | ||
741 | if (!ctx) | |
742 | return; | |
743 | ||
744 | if (to & ~PAGE_MASK) { | |
745 | userfaultfd_ctx_put(ctx); | |
746 | return; | |
747 | } | |
748 | ||
749 | msg_init(&ewq.msg); | |
750 | ||
751 | ewq.msg.event = UFFD_EVENT_REMAP; | |
752 | ewq.msg.arg.remap.from = from; | |
753 | ewq.msg.arg.remap.to = to; | |
754 | ewq.msg.arg.remap.len = len; | |
755 | ||
756 | userfaultfd_event_wait_completion(ctx, &ewq); | |
757 | } | |
758 | ||
70ccb92f | 759 | bool userfaultfd_remove(struct vm_area_struct *vma, |
d811914d | 760 | unsigned long start, unsigned long end) |
05ce7724 PE |
761 | { |
762 | struct mm_struct *mm = vma->vm_mm; | |
763 | struct userfaultfd_ctx *ctx; | |
764 | struct userfaultfd_wait_queue ewq; | |
765 | ||
766 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
d811914d | 767 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
70ccb92f | 768 | return true; |
05ce7724 PE |
769 | |
770 | userfaultfd_ctx_get(ctx); | |
a759a909 | 771 | atomic_inc(&ctx->mmap_changing); |
d8ed45c5 | 772 | mmap_read_unlock(mm); |
05ce7724 | 773 | |
05ce7724 PE |
774 | msg_init(&ewq.msg); |
775 | ||
d811914d MR |
776 | ewq.msg.event = UFFD_EVENT_REMOVE; |
777 | ewq.msg.arg.remove.start = start; | |
778 | ewq.msg.arg.remove.end = end; | |
05ce7724 PE |
779 | |
780 | userfaultfd_event_wait_completion(ctx, &ewq); | |
781 | ||
70ccb92f | 782 | return false; |
05ce7724 PE |
783 | } |
784 | ||
897ab3e0 MR |
785 | static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
786 | unsigned long start, unsigned long end) | |
787 | { | |
788 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
789 | ||
790 | list_for_each_entry(unmap_ctx, unmaps, list) | |
791 | if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && | |
792 | unmap_ctx->end == end) | |
793 | return true; | |
794 | ||
795 | return false; | |
796 | } | |
797 | ||
798 | int userfaultfd_unmap_prep(struct vm_area_struct *vma, | |
799 | unsigned long start, unsigned long end, | |
800 | struct list_head *unmaps) | |
801 | { | |
802 | for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { | |
803 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
804 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; | |
805 | ||
806 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || | |
807 | has_unmap_ctx(ctx, unmaps, start, end)) | |
808 | continue; | |
809 | ||
810 | unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); | |
811 | if (!unmap_ctx) | |
812 | return -ENOMEM; | |
813 | ||
814 | userfaultfd_ctx_get(ctx); | |
a759a909 | 815 | atomic_inc(&ctx->mmap_changing); |
897ab3e0 MR |
816 | unmap_ctx->ctx = ctx; |
817 | unmap_ctx->start = start; | |
818 | unmap_ctx->end = end; | |
819 | list_add_tail(&unmap_ctx->list, unmaps); | |
820 | } | |
821 | ||
822 | return 0; | |
823 | } | |
824 | ||
825 | void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) | |
826 | { | |
827 | struct userfaultfd_unmap_ctx *ctx, *n; | |
828 | struct userfaultfd_wait_queue ewq; | |
829 | ||
830 | list_for_each_entry_safe(ctx, n, uf, list) { | |
831 | msg_init(&ewq.msg); | |
832 | ||
833 | ewq.msg.event = UFFD_EVENT_UNMAP; | |
834 | ewq.msg.arg.remove.start = ctx->start; | |
835 | ewq.msg.arg.remove.end = ctx->end; | |
836 | ||
837 | userfaultfd_event_wait_completion(ctx->ctx, &ewq); | |
838 | ||
839 | list_del(&ctx->list); | |
840 | kfree(ctx); | |
841 | } | |
842 | } | |
843 | ||
86039bd3 AA |
844 | static int userfaultfd_release(struct inode *inode, struct file *file) |
845 | { | |
846 | struct userfaultfd_ctx *ctx = file->private_data; | |
847 | struct mm_struct *mm = ctx->mm; | |
848 | struct vm_area_struct *vma, *prev; | |
849 | /* len == 0 means wake all */ | |
850 | struct userfaultfd_wake_range range = { .len = 0, }; | |
851 | unsigned long new_flags; | |
852 | ||
6aa7de05 | 853 | WRITE_ONCE(ctx->released, true); |
86039bd3 | 854 | |
d2005e3f ON |
855 | if (!mmget_not_zero(mm)) |
856 | goto wakeup; | |
857 | ||
86039bd3 AA |
858 | /* |
859 | * Flush page faults out of all CPUs. NOTE: all page faults | |
860 | * must be retried without returning VM_FAULT_SIGBUS if | |
861 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx | |
c1e8d7c6 | 862 | * changes while handle_userfault released the mmap_lock. So |
86039bd3 | 863 | * it's critical that released is set to true (above), before |
c1e8d7c6 | 864 | * taking the mmap_lock for writing. |
86039bd3 | 865 | */ |
d8ed45c5 | 866 | mmap_write_lock(mm); |
86039bd3 AA |
867 | prev = NULL; |
868 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
869 | cond_resched(); | |
870 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 871 | !!(vma->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
872 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { |
873 | prev = vma; | |
874 | continue; | |
875 | } | |
7677f7fd | 876 | new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; |
4d45e75a JH |
877 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, |
878 | new_flags, vma->anon_vma, | |
879 | vma->vm_file, vma->vm_pgoff, | |
880 | vma_policy(vma), | |
9a10064f | 881 | NULL_VM_UFFD_CTX, vma_anon_name(vma)); |
4d45e75a JH |
882 | if (prev) |
883 | vma = prev; | |
884 | else | |
885 | prev = vma; | |
86039bd3 AA |
886 | vma->vm_flags = new_flags; |
887 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
888 | } | |
d8ed45c5 | 889 | mmap_write_unlock(mm); |
d2005e3f ON |
890 | mmput(mm); |
891 | wakeup: | |
86039bd3 | 892 | /* |
15b726ef | 893 | * After no new page faults can wait on this fault_*wqh, flush |
86039bd3 | 894 | * the last page faults that may have been already waiting on |
15b726ef | 895 | * the fault_*wqh. |
86039bd3 | 896 | */ |
cbcfa130 | 897 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
ac5be6b4 | 898 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
c430d1e8 | 899 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); |
cbcfa130 | 900 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 901 | |
5a18b64e MR |
902 | /* Flush pending events that may still wait on event_wqh */ |
903 | wake_up_all(&ctx->event_wqh); | |
904 | ||
a9a08845 | 905 | wake_up_poll(&ctx->fd_wqh, EPOLLHUP); |
86039bd3 AA |
906 | userfaultfd_ctx_put(ctx); |
907 | return 0; | |
908 | } | |
909 | ||
15b726ef | 910 | /* fault_pending_wqh.lock must be hold by the caller */ |
6dcc27fd PE |
911 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
912 | wait_queue_head_t *wqh) | |
86039bd3 | 913 | { |
ac6424b9 | 914 | wait_queue_entry_t *wq; |
15b726ef | 915 | struct userfaultfd_wait_queue *uwq; |
86039bd3 | 916 | |
456a7378 | 917 | lockdep_assert_held(&wqh->lock); |
86039bd3 | 918 | |
15b726ef | 919 | uwq = NULL; |
6dcc27fd | 920 | if (!waitqueue_active(wqh)) |
15b726ef AA |
921 | goto out; |
922 | /* walk in reverse to provide FIFO behavior to read userfaults */ | |
2055da97 | 923 | wq = list_last_entry(&wqh->head, typeof(*wq), entry); |
15b726ef AA |
924 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
925 | out: | |
926 | return uwq; | |
86039bd3 | 927 | } |
6dcc27fd PE |
928 | |
929 | static inline struct userfaultfd_wait_queue *find_userfault( | |
930 | struct userfaultfd_ctx *ctx) | |
931 | { | |
932 | return find_userfault_in(&ctx->fault_pending_wqh); | |
933 | } | |
86039bd3 | 934 | |
9cd75c3c PE |
935 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
936 | struct userfaultfd_ctx *ctx) | |
937 | { | |
938 | return find_userfault_in(&ctx->event_wqh); | |
939 | } | |
940 | ||
076ccb76 | 941 | static __poll_t userfaultfd_poll(struct file *file, poll_table *wait) |
86039bd3 AA |
942 | { |
943 | struct userfaultfd_ctx *ctx = file->private_data; | |
076ccb76 | 944 | __poll_t ret; |
86039bd3 AA |
945 | |
946 | poll_wait(file, &ctx->fd_wqh, wait); | |
947 | ||
22e5fe2a | 948 | if (!userfaultfd_is_initialized(ctx)) |
a9a08845 | 949 | return EPOLLERR; |
9cd75c3c | 950 | |
22e5fe2a NA |
951 | /* |
952 | * poll() never guarantees that read won't block. | |
953 | * userfaults can be waken before they're read(). | |
954 | */ | |
955 | if (unlikely(!(file->f_flags & O_NONBLOCK))) | |
a9a08845 | 956 | return EPOLLERR; |
22e5fe2a NA |
957 | /* |
958 | * lockless access to see if there are pending faults | |
959 | * __pollwait last action is the add_wait_queue but | |
960 | * the spin_unlock would allow the waitqueue_active to | |
961 | * pass above the actual list_add inside | |
962 | * add_wait_queue critical section. So use a full | |
963 | * memory barrier to serialize the list_add write of | |
964 | * add_wait_queue() with the waitqueue_active read | |
965 | * below. | |
966 | */ | |
967 | ret = 0; | |
968 | smp_mb(); | |
969 | if (waitqueue_active(&ctx->fault_pending_wqh)) | |
970 | ret = EPOLLIN; | |
971 | else if (waitqueue_active(&ctx->event_wqh)) | |
972 | ret = EPOLLIN; | |
973 | ||
974 | return ret; | |
86039bd3 AA |
975 | } |
976 | ||
893e26e6 PE |
977 | static const struct file_operations userfaultfd_fops; |
978 | ||
b537900f DC |
979 | static int resolve_userfault_fork(struct userfaultfd_ctx *new, |
980 | struct inode *inode, | |
893e26e6 PE |
981 | struct uffd_msg *msg) |
982 | { | |
983 | int fd; | |
893e26e6 | 984 | |
b537900f DC |
985 | fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new, |
986 | O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); | |
893e26e6 PE |
987 | if (fd < 0) |
988 | return fd; | |
989 | ||
893e26e6 PE |
990 | msg->arg.reserved.reserved1 = 0; |
991 | msg->arg.fork.ufd = fd; | |
893e26e6 PE |
992 | return 0; |
993 | } | |
994 | ||
86039bd3 | 995 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
b537900f | 996 | struct uffd_msg *msg, struct inode *inode) |
86039bd3 AA |
997 | { |
998 | ssize_t ret; | |
999 | DECLARE_WAITQUEUE(wait, current); | |
15b726ef | 1000 | struct userfaultfd_wait_queue *uwq; |
893e26e6 PE |
1001 | /* |
1002 | * Handling fork event requires sleeping operations, so | |
1003 | * we drop the event_wqh lock, then do these ops, then | |
1004 | * lock it back and wake up the waiter. While the lock is | |
1005 | * dropped the ewq may go away so we keep track of it | |
1006 | * carefully. | |
1007 | */ | |
1008 | LIST_HEAD(fork_event); | |
1009 | struct userfaultfd_ctx *fork_nctx = NULL; | |
86039bd3 | 1010 | |
15b726ef | 1011 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
ae62c16e | 1012 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1013 | __add_wait_queue(&ctx->fd_wqh, &wait); |
1014 | for (;;) { | |
1015 | set_current_state(TASK_INTERRUPTIBLE); | |
15b726ef AA |
1016 | spin_lock(&ctx->fault_pending_wqh.lock); |
1017 | uwq = find_userfault(ctx); | |
1018 | if (uwq) { | |
2c5b7e1b AA |
1019 | /* |
1020 | * Use a seqcount to repeat the lockless check | |
1021 | * in wake_userfault() to avoid missing | |
1022 | * wakeups because during the refile both | |
1023 | * waitqueue could become empty if this is the | |
1024 | * only userfault. | |
1025 | */ | |
1026 | write_seqcount_begin(&ctx->refile_seq); | |
1027 | ||
86039bd3 | 1028 | /* |
15b726ef AA |
1029 | * The fault_pending_wqh.lock prevents the uwq |
1030 | * to disappear from under us. | |
1031 | * | |
1032 | * Refile this userfault from | |
1033 | * fault_pending_wqh to fault_wqh, it's not | |
1034 | * pending anymore after we read it. | |
1035 | * | |
1036 | * Use list_del() by hand (as | |
1037 | * userfaultfd_wake_function also uses | |
1038 | * list_del_init() by hand) to be sure nobody | |
1039 | * changes __remove_wait_queue() to use | |
1040 | * list_del_init() in turn breaking the | |
1041 | * !list_empty_careful() check in | |
2055da97 | 1042 | * handle_userfault(). The uwq->wq.head list |
15b726ef AA |
1043 | * must never be empty at any time during the |
1044 | * refile, or the waitqueue could disappear | |
1045 | * from under us. The "wait_queue_head_t" | |
1046 | * parameter of __remove_wait_queue() is unused | |
1047 | * anyway. | |
86039bd3 | 1048 | */ |
2055da97 | 1049 | list_del(&uwq->wq.entry); |
c430d1e8 | 1050 | add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
15b726ef | 1051 | |
2c5b7e1b AA |
1052 | write_seqcount_end(&ctx->refile_seq); |
1053 | ||
a9b85f94 AA |
1054 | /* careful to always initialize msg if ret == 0 */ |
1055 | *msg = uwq->msg; | |
15b726ef | 1056 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1057 | ret = 0; |
1058 | break; | |
1059 | } | |
15b726ef | 1060 | spin_unlock(&ctx->fault_pending_wqh.lock); |
9cd75c3c PE |
1061 | |
1062 | spin_lock(&ctx->event_wqh.lock); | |
1063 | uwq = find_userfault_evt(ctx); | |
1064 | if (uwq) { | |
1065 | *msg = uwq->msg; | |
1066 | ||
893e26e6 PE |
1067 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
1068 | fork_nctx = (struct userfaultfd_ctx *) | |
1069 | (unsigned long) | |
1070 | uwq->msg.arg.reserved.reserved1; | |
2055da97 | 1071 | list_move(&uwq->wq.entry, &fork_event); |
384632e6 AA |
1072 | /* |
1073 | * fork_nctx can be freed as soon as | |
1074 | * we drop the lock, unless we take a | |
1075 | * reference on it. | |
1076 | */ | |
1077 | userfaultfd_ctx_get(fork_nctx); | |
893e26e6 PE |
1078 | spin_unlock(&ctx->event_wqh.lock); |
1079 | ret = 0; | |
1080 | break; | |
1081 | } | |
1082 | ||
9cd75c3c PE |
1083 | userfaultfd_event_complete(ctx, uwq); |
1084 | spin_unlock(&ctx->event_wqh.lock); | |
1085 | ret = 0; | |
1086 | break; | |
1087 | } | |
1088 | spin_unlock(&ctx->event_wqh.lock); | |
1089 | ||
86039bd3 AA |
1090 | if (signal_pending(current)) { |
1091 | ret = -ERESTARTSYS; | |
1092 | break; | |
1093 | } | |
1094 | if (no_wait) { | |
1095 | ret = -EAGAIN; | |
1096 | break; | |
1097 | } | |
ae62c16e | 1098 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1099 | schedule(); |
ae62c16e | 1100 | spin_lock_irq(&ctx->fd_wqh.lock); |
86039bd3 AA |
1101 | } |
1102 | __remove_wait_queue(&ctx->fd_wqh, &wait); | |
1103 | __set_current_state(TASK_RUNNING); | |
ae62c16e | 1104 | spin_unlock_irq(&ctx->fd_wqh.lock); |
86039bd3 | 1105 | |
893e26e6 | 1106 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
b537900f | 1107 | ret = resolve_userfault_fork(fork_nctx, inode, msg); |
cbcfa130 | 1108 | spin_lock_irq(&ctx->event_wqh.lock); |
384632e6 AA |
1109 | if (!list_empty(&fork_event)) { |
1110 | /* | |
1111 | * The fork thread didn't abort, so we can | |
1112 | * drop the temporary refcount. | |
1113 | */ | |
1114 | userfaultfd_ctx_put(fork_nctx); | |
1115 | ||
1116 | uwq = list_first_entry(&fork_event, | |
1117 | typeof(*uwq), | |
1118 | wq.entry); | |
1119 | /* | |
1120 | * If fork_event list wasn't empty and in turn | |
1121 | * the event wasn't already released by fork | |
1122 | * (the event is allocated on fork kernel | |
1123 | * stack), put the event back to its place in | |
1124 | * the event_wq. fork_event head will be freed | |
1125 | * as soon as we return so the event cannot | |
1126 | * stay queued there no matter the current | |
1127 | * "ret" value. | |
1128 | */ | |
1129 | list_del(&uwq->wq.entry); | |
1130 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); | |
893e26e6 | 1131 | |
384632e6 AA |
1132 | /* |
1133 | * Leave the event in the waitqueue and report | |
1134 | * error to userland if we failed to resolve | |
1135 | * the userfault fork. | |
1136 | */ | |
1137 | if (likely(!ret)) | |
893e26e6 | 1138 | userfaultfd_event_complete(ctx, uwq); |
384632e6 AA |
1139 | } else { |
1140 | /* | |
1141 | * Here the fork thread aborted and the | |
1142 | * refcount from the fork thread on fork_nctx | |
1143 | * has already been released. We still hold | |
1144 | * the reference we took before releasing the | |
1145 | * lock above. If resolve_userfault_fork | |
1146 | * failed we've to drop it because the | |
1147 | * fork_nctx has to be freed in such case. If | |
1148 | * it succeeded we'll hold it because the new | |
1149 | * uffd references it. | |
1150 | */ | |
1151 | if (ret) | |
1152 | userfaultfd_ctx_put(fork_nctx); | |
893e26e6 | 1153 | } |
cbcfa130 | 1154 | spin_unlock_irq(&ctx->event_wqh.lock); |
893e26e6 PE |
1155 | } |
1156 | ||
86039bd3 AA |
1157 | return ret; |
1158 | } | |
1159 | ||
1160 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, | |
1161 | size_t count, loff_t *ppos) | |
1162 | { | |
1163 | struct userfaultfd_ctx *ctx = file->private_data; | |
1164 | ssize_t _ret, ret = 0; | |
a9b85f94 | 1165 | struct uffd_msg msg; |
86039bd3 | 1166 | int no_wait = file->f_flags & O_NONBLOCK; |
b537900f | 1167 | struct inode *inode = file_inode(file); |
86039bd3 | 1168 | |
22e5fe2a | 1169 | if (!userfaultfd_is_initialized(ctx)) |
86039bd3 | 1170 | return -EINVAL; |
86039bd3 AA |
1171 | |
1172 | for (;;) { | |
a9b85f94 | 1173 | if (count < sizeof(msg)) |
86039bd3 | 1174 | return ret ? ret : -EINVAL; |
b537900f | 1175 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg, inode); |
86039bd3 AA |
1176 | if (_ret < 0) |
1177 | return ret ? ret : _ret; | |
a9b85f94 | 1178 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
86039bd3 | 1179 | return ret ? ret : -EFAULT; |
a9b85f94 AA |
1180 | ret += sizeof(msg); |
1181 | buf += sizeof(msg); | |
1182 | count -= sizeof(msg); | |
86039bd3 AA |
1183 | /* |
1184 | * Allow to read more than one fault at time but only | |
1185 | * block if waiting for the very first one. | |
1186 | */ | |
1187 | no_wait = O_NONBLOCK; | |
1188 | } | |
1189 | } | |
1190 | ||
1191 | static void __wake_userfault(struct userfaultfd_ctx *ctx, | |
1192 | struct userfaultfd_wake_range *range) | |
1193 | { | |
cbcfa130 | 1194 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 | 1195 | /* wake all in the range and autoremove */ |
15b726ef | 1196 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
ac5be6b4 | 1197 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
15b726ef AA |
1198 | range); |
1199 | if (waitqueue_active(&ctx->fault_wqh)) | |
c430d1e8 | 1200 | __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); |
cbcfa130 | 1201 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1202 | } |
1203 | ||
1204 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, | |
1205 | struct userfaultfd_wake_range *range) | |
1206 | { | |
2c5b7e1b AA |
1207 | unsigned seq; |
1208 | bool need_wakeup; | |
1209 | ||
86039bd3 AA |
1210 | /* |
1211 | * To be sure waitqueue_active() is not reordered by the CPU | |
1212 | * before the pagetable update, use an explicit SMP memory | |
3e4e28c5 | 1213 | * barrier here. PT lock release or mmap_read_unlock(mm) still |
86039bd3 AA |
1214 | * have release semantics that can allow the |
1215 | * waitqueue_active() to be reordered before the pte update. | |
1216 | */ | |
1217 | smp_mb(); | |
1218 | ||
1219 | /* | |
1220 | * Use waitqueue_active because it's very frequent to | |
1221 | * change the address space atomically even if there are no | |
1222 | * userfaults yet. So we take the spinlock only when we're | |
1223 | * sure we've userfaults to wake. | |
1224 | */ | |
2c5b7e1b AA |
1225 | do { |
1226 | seq = read_seqcount_begin(&ctx->refile_seq); | |
1227 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || | |
1228 | waitqueue_active(&ctx->fault_wqh); | |
1229 | cond_resched(); | |
1230 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); | |
1231 | if (need_wakeup) | |
86039bd3 AA |
1232 | __wake_userfault(ctx, range); |
1233 | } | |
1234 | ||
1235 | static __always_inline int validate_range(struct mm_struct *mm, | |
e71e2ace | 1236 | __u64 start, __u64 len) |
86039bd3 AA |
1237 | { |
1238 | __u64 task_size = mm->task_size; | |
1239 | ||
e71e2ace | 1240 | if (start & ~PAGE_MASK) |
86039bd3 AA |
1241 | return -EINVAL; |
1242 | if (len & ~PAGE_MASK) | |
1243 | return -EINVAL; | |
1244 | if (!len) | |
1245 | return -EINVAL; | |
e71e2ace | 1246 | if (start < mmap_min_addr) |
86039bd3 | 1247 | return -EINVAL; |
e71e2ace | 1248 | if (start >= task_size) |
86039bd3 | 1249 | return -EINVAL; |
e71e2ace | 1250 | if (len > task_size - start) |
86039bd3 AA |
1251 | return -EINVAL; |
1252 | return 0; | |
1253 | } | |
1254 | ||
63b2d417 AA |
1255 | static inline bool vma_can_userfault(struct vm_area_struct *vma, |
1256 | unsigned long vm_flags) | |
ba6907db | 1257 | { |
63b2d417 | 1258 | /* FIXME: add WP support to hugetlbfs and shmem */ |
7677f7fd AR |
1259 | if (vm_flags & VM_UFFD_WP) { |
1260 | if (is_vm_hugetlb_page(vma) || vma_is_shmem(vma)) | |
1261 | return false; | |
1262 | } | |
1263 | ||
1264 | if (vm_flags & VM_UFFD_MINOR) { | |
c949b097 | 1265 | if (!(is_vm_hugetlb_page(vma) || vma_is_shmem(vma))) |
7677f7fd AR |
1266 | return false; |
1267 | } | |
1268 | ||
1269 | return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || | |
1270 | vma_is_shmem(vma); | |
ba6907db MR |
1271 | } |
1272 | ||
86039bd3 AA |
1273 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
1274 | unsigned long arg) | |
1275 | { | |
1276 | struct mm_struct *mm = ctx->mm; | |
1277 | struct vm_area_struct *vma, *prev, *cur; | |
1278 | int ret; | |
1279 | struct uffdio_register uffdio_register; | |
1280 | struct uffdio_register __user *user_uffdio_register; | |
1281 | unsigned long vm_flags, new_flags; | |
1282 | bool found; | |
ce53e8e6 | 1283 | bool basic_ioctls; |
86039bd3 AA |
1284 | unsigned long start, end, vma_end; |
1285 | ||
1286 | user_uffdio_register = (struct uffdio_register __user *) arg; | |
1287 | ||
1288 | ret = -EFAULT; | |
1289 | if (copy_from_user(&uffdio_register, user_uffdio_register, | |
1290 | sizeof(uffdio_register)-sizeof(__u64))) | |
1291 | goto out; | |
1292 | ||
1293 | ret = -EINVAL; | |
1294 | if (!uffdio_register.mode) | |
1295 | goto out; | |
7677f7fd | 1296 | if (uffdio_register.mode & ~UFFD_API_REGISTER_MODES) |
86039bd3 AA |
1297 | goto out; |
1298 | vm_flags = 0; | |
1299 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) | |
1300 | vm_flags |= VM_UFFD_MISSING; | |
00b151f2 PX |
1301 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { |
1302 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP | |
1303 | goto out; | |
1304 | #endif | |
86039bd3 | 1305 | vm_flags |= VM_UFFD_WP; |
00b151f2 | 1306 | } |
7677f7fd AR |
1307 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) { |
1308 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR | |
1309 | goto out; | |
1310 | #endif | |
1311 | vm_flags |= VM_UFFD_MINOR; | |
1312 | } | |
86039bd3 | 1313 | |
e71e2ace | 1314 | ret = validate_range(mm, uffdio_register.range.start, |
86039bd3 AA |
1315 | uffdio_register.range.len); |
1316 | if (ret) | |
1317 | goto out; | |
1318 | ||
1319 | start = uffdio_register.range.start; | |
1320 | end = start + uffdio_register.range.len; | |
1321 | ||
d2005e3f ON |
1322 | ret = -ENOMEM; |
1323 | if (!mmget_not_zero(mm)) | |
1324 | goto out; | |
1325 | ||
d8ed45c5 | 1326 | mmap_write_lock(mm); |
86039bd3 | 1327 | vma = find_vma_prev(mm, start, &prev); |
86039bd3 AA |
1328 | if (!vma) |
1329 | goto out_unlock; | |
1330 | ||
1331 | /* check that there's at least one vma in the range */ | |
1332 | ret = -EINVAL; | |
1333 | if (vma->vm_start >= end) | |
1334 | goto out_unlock; | |
1335 | ||
cab350af MK |
1336 | /* |
1337 | * If the first vma contains huge pages, make sure start address | |
1338 | * is aligned to huge page size. | |
1339 | */ | |
1340 | if (is_vm_hugetlb_page(vma)) { | |
1341 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1342 | ||
1343 | if (start & (vma_hpagesize - 1)) | |
1344 | goto out_unlock; | |
1345 | } | |
1346 | ||
86039bd3 AA |
1347 | /* |
1348 | * Search for not compatible vmas. | |
86039bd3 AA |
1349 | */ |
1350 | found = false; | |
ce53e8e6 | 1351 | basic_ioctls = false; |
86039bd3 AA |
1352 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
1353 | cond_resched(); | |
1354 | ||
1355 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 1356 | !!(cur->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
1357 | |
1358 | /* check not compatible vmas */ | |
1359 | ret = -EINVAL; | |
63b2d417 | 1360 | if (!vma_can_userfault(cur, vm_flags)) |
86039bd3 | 1361 | goto out_unlock; |
29ec9066 AA |
1362 | |
1363 | /* | |
1364 | * UFFDIO_COPY will fill file holes even without | |
1365 | * PROT_WRITE. This check enforces that if this is a | |
1366 | * MAP_SHARED, the process has write permission to the backing | |
1367 | * file. If VM_MAYWRITE is set it also enforces that on a | |
1368 | * MAP_SHARED vma: there is no F_WRITE_SEAL and no further | |
1369 | * F_WRITE_SEAL can be taken until the vma is destroyed. | |
1370 | */ | |
1371 | ret = -EPERM; | |
1372 | if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) | |
1373 | goto out_unlock; | |
1374 | ||
cab350af MK |
1375 | /* |
1376 | * If this vma contains ending address, and huge pages | |
1377 | * check alignment. | |
1378 | */ | |
1379 | if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && | |
1380 | end > cur->vm_start) { | |
1381 | unsigned long vma_hpagesize = vma_kernel_pagesize(cur); | |
1382 | ||
1383 | ret = -EINVAL; | |
1384 | ||
1385 | if (end & (vma_hpagesize - 1)) | |
1386 | goto out_unlock; | |
1387 | } | |
63b2d417 AA |
1388 | if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE)) |
1389 | goto out_unlock; | |
86039bd3 AA |
1390 | |
1391 | /* | |
1392 | * Check that this vma isn't already owned by a | |
1393 | * different userfaultfd. We can't allow more than one | |
1394 | * userfaultfd to own a single vma simultaneously or we | |
1395 | * wouldn't know which one to deliver the userfaults to. | |
1396 | */ | |
1397 | ret = -EBUSY; | |
1398 | if (cur->vm_userfaultfd_ctx.ctx && | |
1399 | cur->vm_userfaultfd_ctx.ctx != ctx) | |
1400 | goto out_unlock; | |
1401 | ||
cab350af MK |
1402 | /* |
1403 | * Note vmas containing huge pages | |
1404 | */ | |
ce53e8e6 MR |
1405 | if (is_vm_hugetlb_page(cur)) |
1406 | basic_ioctls = true; | |
cab350af | 1407 | |
86039bd3 AA |
1408 | found = true; |
1409 | } | |
1410 | BUG_ON(!found); | |
1411 | ||
1412 | if (vma->vm_start < start) | |
1413 | prev = vma; | |
1414 | ||
1415 | ret = 0; | |
1416 | do { | |
1417 | cond_resched(); | |
1418 | ||
63b2d417 | 1419 | BUG_ON(!vma_can_userfault(vma, vm_flags)); |
86039bd3 AA |
1420 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
1421 | vma->vm_userfaultfd_ctx.ctx != ctx); | |
29ec9066 | 1422 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
86039bd3 AA |
1423 | |
1424 | /* | |
1425 | * Nothing to do: this vma is already registered into this | |
1426 | * userfaultfd and with the right tracking mode too. | |
1427 | */ | |
1428 | if (vma->vm_userfaultfd_ctx.ctx == ctx && | |
1429 | (vma->vm_flags & vm_flags) == vm_flags) | |
1430 | goto skip; | |
1431 | ||
1432 | if (vma->vm_start > start) | |
1433 | start = vma->vm_start; | |
1434 | vma_end = min(end, vma->vm_end); | |
1435 | ||
7677f7fd | 1436 | new_flags = (vma->vm_flags & ~__VM_UFFD_FLAGS) | vm_flags; |
86039bd3 AA |
1437 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
1438 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1439 | vma_policy(vma), | |
9a10064f CC |
1440 | ((struct vm_userfaultfd_ctx){ ctx }), |
1441 | vma_anon_name(vma)); | |
86039bd3 AA |
1442 | if (prev) { |
1443 | vma = prev; | |
1444 | goto next; | |
1445 | } | |
1446 | if (vma->vm_start < start) { | |
1447 | ret = split_vma(mm, vma, start, 1); | |
1448 | if (ret) | |
1449 | break; | |
1450 | } | |
1451 | if (vma->vm_end > end) { | |
1452 | ret = split_vma(mm, vma, end, 0); | |
1453 | if (ret) | |
1454 | break; | |
1455 | } | |
1456 | next: | |
1457 | /* | |
1458 | * In the vma_merge() successful mprotect-like case 8: | |
1459 | * the next vma was merged into the current one and | |
1460 | * the current one has not been updated yet. | |
1461 | */ | |
1462 | vma->vm_flags = new_flags; | |
1463 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
1464 | ||
6dfeaff9 PX |
1465 | if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma)) |
1466 | hugetlb_unshare_all_pmds(vma); | |
1467 | ||
86039bd3 AA |
1468 | skip: |
1469 | prev = vma; | |
1470 | start = vma->vm_end; | |
1471 | vma = vma->vm_next; | |
1472 | } while (vma && vma->vm_start < end); | |
1473 | out_unlock: | |
d8ed45c5 | 1474 | mmap_write_unlock(mm); |
d2005e3f | 1475 | mmput(mm); |
86039bd3 | 1476 | if (!ret) { |
14819305 PX |
1477 | __u64 ioctls_out; |
1478 | ||
1479 | ioctls_out = basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : | |
1480 | UFFD_API_RANGE_IOCTLS; | |
1481 | ||
1482 | /* | |
1483 | * Declare the WP ioctl only if the WP mode is | |
1484 | * specified and all checks passed with the range | |
1485 | */ | |
1486 | if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)) | |
1487 | ioctls_out &= ~((__u64)1 << _UFFDIO_WRITEPROTECT); | |
1488 | ||
f6191471 AR |
1489 | /* CONTINUE ioctl is only supported for MINOR ranges. */ |
1490 | if (!(uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR)) | |
1491 | ioctls_out &= ~((__u64)1 << _UFFDIO_CONTINUE); | |
1492 | ||
86039bd3 AA |
1493 | /* |
1494 | * Now that we scanned all vmas we can already tell | |
1495 | * userland which ioctls methods are guaranteed to | |
1496 | * succeed on this range. | |
1497 | */ | |
14819305 | 1498 | if (put_user(ioctls_out, &user_uffdio_register->ioctls)) |
86039bd3 AA |
1499 | ret = -EFAULT; |
1500 | } | |
1501 | out: | |
1502 | return ret; | |
1503 | } | |
1504 | ||
1505 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, | |
1506 | unsigned long arg) | |
1507 | { | |
1508 | struct mm_struct *mm = ctx->mm; | |
1509 | struct vm_area_struct *vma, *prev, *cur; | |
1510 | int ret; | |
1511 | struct uffdio_range uffdio_unregister; | |
1512 | unsigned long new_flags; | |
1513 | bool found; | |
1514 | unsigned long start, end, vma_end; | |
1515 | const void __user *buf = (void __user *)arg; | |
1516 | ||
1517 | ret = -EFAULT; | |
1518 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) | |
1519 | goto out; | |
1520 | ||
e71e2ace | 1521 | ret = validate_range(mm, uffdio_unregister.start, |
86039bd3 AA |
1522 | uffdio_unregister.len); |
1523 | if (ret) | |
1524 | goto out; | |
1525 | ||
1526 | start = uffdio_unregister.start; | |
1527 | end = start + uffdio_unregister.len; | |
1528 | ||
d2005e3f ON |
1529 | ret = -ENOMEM; |
1530 | if (!mmget_not_zero(mm)) | |
1531 | goto out; | |
1532 | ||
d8ed45c5 | 1533 | mmap_write_lock(mm); |
86039bd3 | 1534 | vma = find_vma_prev(mm, start, &prev); |
86039bd3 AA |
1535 | if (!vma) |
1536 | goto out_unlock; | |
1537 | ||
1538 | /* check that there's at least one vma in the range */ | |
1539 | ret = -EINVAL; | |
1540 | if (vma->vm_start >= end) | |
1541 | goto out_unlock; | |
1542 | ||
cab350af MK |
1543 | /* |
1544 | * If the first vma contains huge pages, make sure start address | |
1545 | * is aligned to huge page size. | |
1546 | */ | |
1547 | if (is_vm_hugetlb_page(vma)) { | |
1548 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1549 | ||
1550 | if (start & (vma_hpagesize - 1)) | |
1551 | goto out_unlock; | |
1552 | } | |
1553 | ||
86039bd3 AA |
1554 | /* |
1555 | * Search for not compatible vmas. | |
86039bd3 AA |
1556 | */ |
1557 | found = false; | |
1558 | ret = -EINVAL; | |
1559 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { | |
1560 | cond_resched(); | |
1561 | ||
1562 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
7677f7fd | 1563 | !!(cur->vm_flags & __VM_UFFD_FLAGS)); |
86039bd3 AA |
1564 | |
1565 | /* | |
1566 | * Check not compatible vmas, not strictly required | |
1567 | * here as not compatible vmas cannot have an | |
1568 | * userfaultfd_ctx registered on them, but this | |
1569 | * provides for more strict behavior to notice | |
1570 | * unregistration errors. | |
1571 | */ | |
63b2d417 | 1572 | if (!vma_can_userfault(cur, cur->vm_flags)) |
86039bd3 AA |
1573 | goto out_unlock; |
1574 | ||
1575 | found = true; | |
1576 | } | |
1577 | BUG_ON(!found); | |
1578 | ||
1579 | if (vma->vm_start < start) | |
1580 | prev = vma; | |
1581 | ||
1582 | ret = 0; | |
1583 | do { | |
1584 | cond_resched(); | |
1585 | ||
63b2d417 | 1586 | BUG_ON(!vma_can_userfault(vma, vma->vm_flags)); |
86039bd3 AA |
1587 | |
1588 | /* | |
1589 | * Nothing to do: this vma is already registered into this | |
1590 | * userfaultfd and with the right tracking mode too. | |
1591 | */ | |
1592 | if (!vma->vm_userfaultfd_ctx.ctx) | |
1593 | goto skip; | |
1594 | ||
01e881f5 AA |
1595 | WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); |
1596 | ||
86039bd3 AA |
1597 | if (vma->vm_start > start) |
1598 | start = vma->vm_start; | |
1599 | vma_end = min(end, vma->vm_end); | |
1600 | ||
09fa5296 AA |
1601 | if (userfaultfd_missing(vma)) { |
1602 | /* | |
1603 | * Wake any concurrent pending userfault while | |
1604 | * we unregister, so they will not hang | |
1605 | * permanently and it avoids userland to call | |
1606 | * UFFDIO_WAKE explicitly. | |
1607 | */ | |
1608 | struct userfaultfd_wake_range range; | |
1609 | range.start = start; | |
1610 | range.len = vma_end - start; | |
1611 | wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); | |
1612 | } | |
1613 | ||
7677f7fd | 1614 | new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS; |
86039bd3 AA |
1615 | prev = vma_merge(mm, prev, start, vma_end, new_flags, |
1616 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1617 | vma_policy(vma), | |
9a10064f | 1618 | NULL_VM_UFFD_CTX, vma_anon_name(vma)); |
86039bd3 AA |
1619 | if (prev) { |
1620 | vma = prev; | |
1621 | goto next; | |
1622 | } | |
1623 | if (vma->vm_start < start) { | |
1624 | ret = split_vma(mm, vma, start, 1); | |
1625 | if (ret) | |
1626 | break; | |
1627 | } | |
1628 | if (vma->vm_end > end) { | |
1629 | ret = split_vma(mm, vma, end, 0); | |
1630 | if (ret) | |
1631 | break; | |
1632 | } | |
1633 | next: | |
1634 | /* | |
1635 | * In the vma_merge() successful mprotect-like case 8: | |
1636 | * the next vma was merged into the current one and | |
1637 | * the current one has not been updated yet. | |
1638 | */ | |
1639 | vma->vm_flags = new_flags; | |
1640 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
1641 | ||
1642 | skip: | |
1643 | prev = vma; | |
1644 | start = vma->vm_end; | |
1645 | vma = vma->vm_next; | |
1646 | } while (vma && vma->vm_start < end); | |
1647 | out_unlock: | |
d8ed45c5 | 1648 | mmap_write_unlock(mm); |
d2005e3f | 1649 | mmput(mm); |
86039bd3 AA |
1650 | out: |
1651 | return ret; | |
1652 | } | |
1653 | ||
1654 | /* | |
ba85c702 AA |
1655 | * userfaultfd_wake may be used in combination with the |
1656 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. | |
86039bd3 AA |
1657 | */ |
1658 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, | |
1659 | unsigned long arg) | |
1660 | { | |
1661 | int ret; | |
1662 | struct uffdio_range uffdio_wake; | |
1663 | struct userfaultfd_wake_range range; | |
1664 | const void __user *buf = (void __user *)arg; | |
1665 | ||
1666 | ret = -EFAULT; | |
1667 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) | |
1668 | goto out; | |
1669 | ||
e71e2ace | 1670 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); |
86039bd3 AA |
1671 | if (ret) |
1672 | goto out; | |
1673 | ||
1674 | range.start = uffdio_wake.start; | |
1675 | range.len = uffdio_wake.len; | |
1676 | ||
1677 | /* | |
1678 | * len == 0 means wake all and we don't want to wake all here, | |
1679 | * so check it again to be sure. | |
1680 | */ | |
1681 | VM_BUG_ON(!range.len); | |
1682 | ||
1683 | wake_userfault(ctx, &range); | |
1684 | ret = 0; | |
1685 | ||
1686 | out: | |
1687 | return ret; | |
1688 | } | |
1689 | ||
ad465cae AA |
1690 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
1691 | unsigned long arg) | |
1692 | { | |
1693 | __s64 ret; | |
1694 | struct uffdio_copy uffdio_copy; | |
1695 | struct uffdio_copy __user *user_uffdio_copy; | |
1696 | struct userfaultfd_wake_range range; | |
1697 | ||
1698 | user_uffdio_copy = (struct uffdio_copy __user *) arg; | |
1699 | ||
df2cc96e | 1700 | ret = -EAGAIN; |
a759a909 | 1701 | if (atomic_read(&ctx->mmap_changing)) |
df2cc96e MR |
1702 | goto out; |
1703 | ||
ad465cae AA |
1704 | ret = -EFAULT; |
1705 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, | |
1706 | /* don't copy "copy" last field */ | |
1707 | sizeof(uffdio_copy)-sizeof(__s64))) | |
1708 | goto out; | |
1709 | ||
e71e2ace | 1710 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); |
ad465cae AA |
1711 | if (ret) |
1712 | goto out; | |
1713 | /* | |
1714 | * double check for wraparound just in case. copy_from_user() | |
1715 | * will later check uffdio_copy.src + uffdio_copy.len to fit | |
1716 | * in the userland range. | |
1717 | */ | |
1718 | ret = -EINVAL; | |
1719 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) | |
1720 | goto out; | |
72981e0e | 1721 | if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP)) |
ad465cae | 1722 | goto out; |
d2005e3f ON |
1723 | if (mmget_not_zero(ctx->mm)) { |
1724 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, | |
72981e0e AA |
1725 | uffdio_copy.len, &ctx->mmap_changing, |
1726 | uffdio_copy.mode); | |
d2005e3f | 1727 | mmput(ctx->mm); |
96333187 | 1728 | } else { |
e86b298b | 1729 | return -ESRCH; |
d2005e3f | 1730 | } |
ad465cae AA |
1731 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
1732 | return -EFAULT; | |
1733 | if (ret < 0) | |
1734 | goto out; | |
1735 | BUG_ON(!ret); | |
1736 | /* len == 0 would wake all */ | |
1737 | range.len = ret; | |
1738 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { | |
1739 | range.start = uffdio_copy.dst; | |
1740 | wake_userfault(ctx, &range); | |
1741 | } | |
1742 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; | |
1743 | out: | |
1744 | return ret; | |
1745 | } | |
1746 | ||
1747 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, | |
1748 | unsigned long arg) | |
1749 | { | |
1750 | __s64 ret; | |
1751 | struct uffdio_zeropage uffdio_zeropage; | |
1752 | struct uffdio_zeropage __user *user_uffdio_zeropage; | |
1753 | struct userfaultfd_wake_range range; | |
1754 | ||
1755 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; | |
1756 | ||
df2cc96e | 1757 | ret = -EAGAIN; |
a759a909 | 1758 | if (atomic_read(&ctx->mmap_changing)) |
df2cc96e MR |
1759 | goto out; |
1760 | ||
ad465cae AA |
1761 | ret = -EFAULT; |
1762 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, | |
1763 | /* don't copy "zeropage" last field */ | |
1764 | sizeof(uffdio_zeropage)-sizeof(__s64))) | |
1765 | goto out; | |
1766 | ||
e71e2ace | 1767 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, |
ad465cae AA |
1768 | uffdio_zeropage.range.len); |
1769 | if (ret) | |
1770 | goto out; | |
1771 | ret = -EINVAL; | |
1772 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) | |
1773 | goto out; | |
1774 | ||
d2005e3f ON |
1775 | if (mmget_not_zero(ctx->mm)) { |
1776 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, | |
df2cc96e MR |
1777 | uffdio_zeropage.range.len, |
1778 | &ctx->mmap_changing); | |
d2005e3f | 1779 | mmput(ctx->mm); |
9d95aa4b | 1780 | } else { |
e86b298b | 1781 | return -ESRCH; |
d2005e3f | 1782 | } |
ad465cae AA |
1783 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
1784 | return -EFAULT; | |
1785 | if (ret < 0) | |
1786 | goto out; | |
1787 | /* len == 0 would wake all */ | |
1788 | BUG_ON(!ret); | |
1789 | range.len = ret; | |
1790 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { | |
1791 | range.start = uffdio_zeropage.range.start; | |
1792 | wake_userfault(ctx, &range); | |
1793 | } | |
1794 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; | |
1795 | out: | |
1796 | return ret; | |
1797 | } | |
1798 | ||
63b2d417 AA |
1799 | static int userfaultfd_writeprotect(struct userfaultfd_ctx *ctx, |
1800 | unsigned long arg) | |
1801 | { | |
1802 | int ret; | |
1803 | struct uffdio_writeprotect uffdio_wp; | |
1804 | struct uffdio_writeprotect __user *user_uffdio_wp; | |
1805 | struct userfaultfd_wake_range range; | |
23080e27 | 1806 | bool mode_wp, mode_dontwake; |
63b2d417 | 1807 | |
a759a909 | 1808 | if (atomic_read(&ctx->mmap_changing)) |
63b2d417 AA |
1809 | return -EAGAIN; |
1810 | ||
1811 | user_uffdio_wp = (struct uffdio_writeprotect __user *) arg; | |
1812 | ||
1813 | if (copy_from_user(&uffdio_wp, user_uffdio_wp, | |
1814 | sizeof(struct uffdio_writeprotect))) | |
1815 | return -EFAULT; | |
1816 | ||
e71e2ace | 1817 | ret = validate_range(ctx->mm, uffdio_wp.range.start, |
63b2d417 AA |
1818 | uffdio_wp.range.len); |
1819 | if (ret) | |
1820 | return ret; | |
1821 | ||
1822 | if (uffdio_wp.mode & ~(UFFDIO_WRITEPROTECT_MODE_DONTWAKE | | |
1823 | UFFDIO_WRITEPROTECT_MODE_WP)) | |
1824 | return -EINVAL; | |
23080e27 PX |
1825 | |
1826 | mode_wp = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_WP; | |
1827 | mode_dontwake = uffdio_wp.mode & UFFDIO_WRITEPROTECT_MODE_DONTWAKE; | |
1828 | ||
1829 | if (mode_wp && mode_dontwake) | |
63b2d417 AA |
1830 | return -EINVAL; |
1831 | ||
cb185d5f NA |
1832 | if (mmget_not_zero(ctx->mm)) { |
1833 | ret = mwriteprotect_range(ctx->mm, uffdio_wp.range.start, | |
1834 | uffdio_wp.range.len, mode_wp, | |
1835 | &ctx->mmap_changing); | |
1836 | mmput(ctx->mm); | |
1837 | } else { | |
1838 | return -ESRCH; | |
1839 | } | |
1840 | ||
63b2d417 AA |
1841 | if (ret) |
1842 | return ret; | |
1843 | ||
23080e27 | 1844 | if (!mode_wp && !mode_dontwake) { |
63b2d417 AA |
1845 | range.start = uffdio_wp.range.start; |
1846 | range.len = uffdio_wp.range.len; | |
1847 | wake_userfault(ctx, &range); | |
1848 | } | |
1849 | return ret; | |
1850 | } | |
1851 | ||
f6191471 AR |
1852 | static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg) |
1853 | { | |
1854 | __s64 ret; | |
1855 | struct uffdio_continue uffdio_continue; | |
1856 | struct uffdio_continue __user *user_uffdio_continue; | |
1857 | struct userfaultfd_wake_range range; | |
1858 | ||
1859 | user_uffdio_continue = (struct uffdio_continue __user *)arg; | |
1860 | ||
1861 | ret = -EAGAIN; | |
a759a909 | 1862 | if (atomic_read(&ctx->mmap_changing)) |
f6191471 AR |
1863 | goto out; |
1864 | ||
1865 | ret = -EFAULT; | |
1866 | if (copy_from_user(&uffdio_continue, user_uffdio_continue, | |
1867 | /* don't copy the output fields */ | |
1868 | sizeof(uffdio_continue) - (sizeof(__s64)))) | |
1869 | goto out; | |
1870 | ||
e71e2ace | 1871 | ret = validate_range(ctx->mm, uffdio_continue.range.start, |
f6191471 AR |
1872 | uffdio_continue.range.len); |
1873 | if (ret) | |
1874 | goto out; | |
1875 | ||
1876 | ret = -EINVAL; | |
1877 | /* double check for wraparound just in case. */ | |
1878 | if (uffdio_continue.range.start + uffdio_continue.range.len <= | |
1879 | uffdio_continue.range.start) { | |
1880 | goto out; | |
1881 | } | |
1882 | if (uffdio_continue.mode & ~UFFDIO_CONTINUE_MODE_DONTWAKE) | |
1883 | goto out; | |
1884 | ||
1885 | if (mmget_not_zero(ctx->mm)) { | |
1886 | ret = mcopy_continue(ctx->mm, uffdio_continue.range.start, | |
1887 | uffdio_continue.range.len, | |
1888 | &ctx->mmap_changing); | |
1889 | mmput(ctx->mm); | |
1890 | } else { | |
1891 | return -ESRCH; | |
1892 | } | |
1893 | ||
1894 | if (unlikely(put_user(ret, &user_uffdio_continue->mapped))) | |
1895 | return -EFAULT; | |
1896 | if (ret < 0) | |
1897 | goto out; | |
1898 | ||
1899 | /* len == 0 would wake all */ | |
1900 | BUG_ON(!ret); | |
1901 | range.len = ret; | |
1902 | if (!(uffdio_continue.mode & UFFDIO_CONTINUE_MODE_DONTWAKE)) { | |
1903 | range.start = uffdio_continue.range.start; | |
1904 | wake_userfault(ctx, &range); | |
1905 | } | |
1906 | ret = range.len == uffdio_continue.range.len ? 0 : -EAGAIN; | |
1907 | ||
1908 | out: | |
1909 | return ret; | |
1910 | } | |
1911 | ||
9cd75c3c PE |
1912 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
1913 | { | |
1914 | /* | |
22e5fe2a NA |
1915 | * For the current set of features the bits just coincide. Set |
1916 | * UFFD_FEATURE_INITIALIZED to mark the features as enabled. | |
9cd75c3c | 1917 | */ |
22e5fe2a | 1918 | return (unsigned int)user_features | UFFD_FEATURE_INITIALIZED; |
9cd75c3c PE |
1919 | } |
1920 | ||
86039bd3 AA |
1921 | /* |
1922 | * userland asks for a certain API version and we return which bits | |
1923 | * and ioctl commands are implemented in this kernel for such API | |
1924 | * version or -EINVAL if unknown. | |
1925 | */ | |
1926 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, | |
1927 | unsigned long arg) | |
1928 | { | |
1929 | struct uffdio_api uffdio_api; | |
1930 | void __user *buf = (void __user *)arg; | |
22e5fe2a | 1931 | unsigned int ctx_features; |
86039bd3 | 1932 | int ret; |
65603144 | 1933 | __u64 features; |
86039bd3 | 1934 | |
86039bd3 | 1935 | ret = -EFAULT; |
a9b85f94 | 1936 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
86039bd3 | 1937 | goto out; |
65603144 | 1938 | features = uffdio_api.features; |
3c1c24d9 MR |
1939 | ret = -EINVAL; |
1940 | if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) | |
1941 | goto err_out; | |
1942 | ret = -EPERM; | |
1943 | if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) | |
1944 | goto err_out; | |
65603144 AA |
1945 | /* report all available features and ioctls to userland */ |
1946 | uffdio_api.features = UFFD_API_FEATURES; | |
7677f7fd | 1947 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR |
964ab004 AR |
1948 | uffdio_api.features &= |
1949 | ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); | |
00b151f2 PX |
1950 | #endif |
1951 | #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP | |
1952 | uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP; | |
7677f7fd | 1953 | #endif |
86039bd3 AA |
1954 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
1955 | ret = -EFAULT; | |
1956 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1957 | goto out; | |
22e5fe2a | 1958 | |
65603144 | 1959 | /* only enable the requested features for this uffd context */ |
22e5fe2a NA |
1960 | ctx_features = uffd_ctx_features(features); |
1961 | ret = -EINVAL; | |
1962 | if (cmpxchg(&ctx->features, 0, ctx_features) != 0) | |
1963 | goto err_out; | |
1964 | ||
86039bd3 AA |
1965 | ret = 0; |
1966 | out: | |
1967 | return ret; | |
3c1c24d9 MR |
1968 | err_out: |
1969 | memset(&uffdio_api, 0, sizeof(uffdio_api)); | |
1970 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1971 | ret = -EFAULT; | |
1972 | goto out; | |
86039bd3 AA |
1973 | } |
1974 | ||
1975 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, | |
1976 | unsigned long arg) | |
1977 | { | |
1978 | int ret = -EINVAL; | |
1979 | struct userfaultfd_ctx *ctx = file->private_data; | |
1980 | ||
22e5fe2a | 1981 | if (cmd != UFFDIO_API && !userfaultfd_is_initialized(ctx)) |
e6485a47 AA |
1982 | return -EINVAL; |
1983 | ||
86039bd3 AA |
1984 | switch(cmd) { |
1985 | case UFFDIO_API: | |
1986 | ret = userfaultfd_api(ctx, arg); | |
1987 | break; | |
1988 | case UFFDIO_REGISTER: | |
1989 | ret = userfaultfd_register(ctx, arg); | |
1990 | break; | |
1991 | case UFFDIO_UNREGISTER: | |
1992 | ret = userfaultfd_unregister(ctx, arg); | |
1993 | break; | |
1994 | case UFFDIO_WAKE: | |
1995 | ret = userfaultfd_wake(ctx, arg); | |
1996 | break; | |
ad465cae AA |
1997 | case UFFDIO_COPY: |
1998 | ret = userfaultfd_copy(ctx, arg); | |
1999 | break; | |
2000 | case UFFDIO_ZEROPAGE: | |
2001 | ret = userfaultfd_zeropage(ctx, arg); | |
2002 | break; | |
63b2d417 AA |
2003 | case UFFDIO_WRITEPROTECT: |
2004 | ret = userfaultfd_writeprotect(ctx, arg); | |
2005 | break; | |
f6191471 AR |
2006 | case UFFDIO_CONTINUE: |
2007 | ret = userfaultfd_continue(ctx, arg); | |
2008 | break; | |
86039bd3 AA |
2009 | } |
2010 | return ret; | |
2011 | } | |
2012 | ||
2013 | #ifdef CONFIG_PROC_FS | |
2014 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) | |
2015 | { | |
2016 | struct userfaultfd_ctx *ctx = f->private_data; | |
ac6424b9 | 2017 | wait_queue_entry_t *wq; |
86039bd3 AA |
2018 | unsigned long pending = 0, total = 0; |
2019 | ||
cbcfa130 | 2020 | spin_lock_irq(&ctx->fault_pending_wqh.lock); |
2055da97 | 2021 | list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { |
15b726ef AA |
2022 | pending++; |
2023 | total++; | |
2024 | } | |
2055da97 | 2025 | list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { |
86039bd3 AA |
2026 | total++; |
2027 | } | |
cbcfa130 | 2028 | spin_unlock_irq(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
2029 | |
2030 | /* | |
2031 | * If more protocols will be added, there will be all shown | |
2032 | * separated by a space. Like this: | |
2033 | * protocols: aa:... bb:... | |
2034 | */ | |
2035 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", | |
045098e9 | 2036 | pending, total, UFFD_API, ctx->features, |
86039bd3 AA |
2037 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
2038 | } | |
2039 | #endif | |
2040 | ||
2041 | static const struct file_operations userfaultfd_fops = { | |
2042 | #ifdef CONFIG_PROC_FS | |
2043 | .show_fdinfo = userfaultfd_show_fdinfo, | |
2044 | #endif | |
2045 | .release = userfaultfd_release, | |
2046 | .poll = userfaultfd_poll, | |
2047 | .read = userfaultfd_read, | |
2048 | .unlocked_ioctl = userfaultfd_ioctl, | |
1832f2d8 | 2049 | .compat_ioctl = compat_ptr_ioctl, |
86039bd3 AA |
2050 | .llseek = noop_llseek, |
2051 | }; | |
2052 | ||
3004ec9c AA |
2053 | static void init_once_userfaultfd_ctx(void *mem) |
2054 | { | |
2055 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; | |
2056 | ||
2057 | init_waitqueue_head(&ctx->fault_pending_wqh); | |
2058 | init_waitqueue_head(&ctx->fault_wqh); | |
9cd75c3c | 2059 | init_waitqueue_head(&ctx->event_wqh); |
3004ec9c | 2060 | init_waitqueue_head(&ctx->fd_wqh); |
2ca97ac8 | 2061 | seqcount_spinlock_init(&ctx->refile_seq, &ctx->fault_pending_wqh.lock); |
3004ec9c AA |
2062 | } |
2063 | ||
284cd241 | 2064 | SYSCALL_DEFINE1(userfaultfd, int, flags) |
86039bd3 | 2065 | { |
86039bd3 | 2066 | struct userfaultfd_ctx *ctx; |
284cd241 | 2067 | int fd; |
86039bd3 | 2068 | |
d0d4730a LG |
2069 | if (!sysctl_unprivileged_userfaultfd && |
2070 | (flags & UFFD_USER_MODE_ONLY) == 0 && | |
2071 | !capable(CAP_SYS_PTRACE)) { | |
2072 | printk_once(KERN_WARNING "uffd: Set unprivileged_userfaultfd " | |
2073 | "sysctl knob to 1 if kernel faults must be handled " | |
2074 | "without obtaining CAP_SYS_PTRACE capability\n"); | |
cefdca0a | 2075 | return -EPERM; |
d0d4730a | 2076 | } |
cefdca0a | 2077 | |
86039bd3 AA |
2078 | BUG_ON(!current->mm); |
2079 | ||
2080 | /* Check the UFFD_* constants for consistency. */ | |
37cd0575 | 2081 | BUILD_BUG_ON(UFFD_USER_MODE_ONLY & UFFD_SHARED_FCNTL_FLAGS); |
86039bd3 AA |
2082 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); |
2083 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); | |
2084 | ||
37cd0575 | 2085 | if (flags & ~(UFFD_SHARED_FCNTL_FLAGS | UFFD_USER_MODE_ONLY)) |
284cd241 | 2086 | return -EINVAL; |
86039bd3 | 2087 | |
3004ec9c | 2088 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
86039bd3 | 2089 | if (!ctx) |
284cd241 | 2090 | return -ENOMEM; |
86039bd3 | 2091 | |
ca880420 | 2092 | refcount_set(&ctx->refcount, 1); |
86039bd3 | 2093 | ctx->flags = flags; |
9cd75c3c | 2094 | ctx->features = 0; |
86039bd3 | 2095 | ctx->released = false; |
a759a909 | 2096 | atomic_set(&ctx->mmap_changing, 0); |
86039bd3 AA |
2097 | ctx->mm = current->mm; |
2098 | /* prevent the mm struct to be freed */ | |
f1f10076 | 2099 | mmgrab(ctx->mm); |
86039bd3 | 2100 | |
b537900f DC |
2101 | fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx, |
2102 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); | |
284cd241 | 2103 | if (fd < 0) { |
d2005e3f | 2104 | mmdrop(ctx->mm); |
3004ec9c | 2105 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
c03e946f | 2106 | } |
86039bd3 | 2107 | return fd; |
86039bd3 | 2108 | } |
3004ec9c AA |
2109 | |
2110 | static int __init userfaultfd_init(void) | |
2111 | { | |
2112 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", | |
2113 | sizeof(struct userfaultfd_ctx), | |
2114 | 0, | |
2115 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, | |
2116 | init_once_userfaultfd_ctx); | |
2117 | return 0; | |
2118 | } | |
2119 | __initcall(userfaultfd_init); |