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Commit | Line | Data |
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86039bd3 AA |
1 | /* |
2 | * fs/userfaultfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * Copyright (C) 2008-2009 Red Hat, Inc. | |
6 | * Copyright (C) 2015 Red Hat, Inc. | |
7 | * | |
8 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
9 | * the COPYING file in the top-level directory. | |
10 | * | |
11 | * Some part derived from fs/eventfd.c (anon inode setup) and | |
12 | * mm/ksm.c (mm hashing). | |
13 | */ | |
14 | ||
9cd75c3c | 15 | #include <linux/list.h> |
86039bd3 | 16 | #include <linux/hashtable.h> |
174cd4b1 | 17 | #include <linux/sched/signal.h> |
6e84f315 | 18 | #include <linux/sched/mm.h> |
86039bd3 AA |
19 | #include <linux/mm.h> |
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 | |
3004ec9c AA |
33 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
34 | ||
86039bd3 AA |
35 | enum userfaultfd_state { |
36 | UFFD_STATE_WAIT_API, | |
37 | UFFD_STATE_RUNNING, | |
38 | }; | |
39 | ||
3004ec9c AA |
40 | /* |
41 | * Start with fault_pending_wqh and fault_wqh so they're more likely | |
42 | * to be in the same cacheline. | |
43 | */ | |
86039bd3 | 44 | struct userfaultfd_ctx { |
15b726ef AA |
45 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
46 | wait_queue_head_t fault_pending_wqh; | |
47 | /* waitqueue head for the userfaults */ | |
86039bd3 AA |
48 | wait_queue_head_t fault_wqh; |
49 | /* waitqueue head for the pseudo fd to wakeup poll/read */ | |
50 | wait_queue_head_t fd_wqh; | |
9cd75c3c PE |
51 | /* waitqueue head for events */ |
52 | wait_queue_head_t event_wqh; | |
2c5b7e1b AA |
53 | /* a refile sequence protected by fault_pending_wqh lock */ |
54 | struct seqcount refile_seq; | |
3004ec9c AA |
55 | /* pseudo fd refcounting */ |
56 | atomic_t refcount; | |
86039bd3 AA |
57 | /* userfaultfd syscall flags */ |
58 | unsigned int flags; | |
9cd75c3c PE |
59 | /* features requested from the userspace */ |
60 | unsigned int features; | |
86039bd3 AA |
61 | /* state machine */ |
62 | enum userfaultfd_state state; | |
63 | /* released */ | |
64 | bool released; | |
65 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ | |
66 | struct mm_struct *mm; | |
67 | }; | |
68 | ||
893e26e6 PE |
69 | struct userfaultfd_fork_ctx { |
70 | struct userfaultfd_ctx *orig; | |
71 | struct userfaultfd_ctx *new; | |
72 | struct list_head list; | |
73 | }; | |
74 | ||
897ab3e0 MR |
75 | struct userfaultfd_unmap_ctx { |
76 | struct userfaultfd_ctx *ctx; | |
77 | unsigned long start; | |
78 | unsigned long end; | |
79 | struct list_head list; | |
80 | }; | |
81 | ||
86039bd3 | 82 | struct userfaultfd_wait_queue { |
a9b85f94 | 83 | struct uffd_msg msg; |
ac6424b9 | 84 | wait_queue_entry_t wq; |
86039bd3 | 85 | struct userfaultfd_ctx *ctx; |
15a77c6f | 86 | bool waken; |
86039bd3 AA |
87 | }; |
88 | ||
89 | struct userfaultfd_wake_range { | |
90 | unsigned long start; | |
91 | unsigned long len; | |
92 | }; | |
93 | ||
ac6424b9 | 94 | static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode, |
86039bd3 AA |
95 | int wake_flags, void *key) |
96 | { | |
97 | struct userfaultfd_wake_range *range = key; | |
98 | int ret; | |
99 | struct userfaultfd_wait_queue *uwq; | |
100 | unsigned long start, len; | |
101 | ||
102 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
103 | ret = 0; | |
86039bd3 AA |
104 | /* len == 0 means wake all */ |
105 | start = range->start; | |
106 | len = range->len; | |
a9b85f94 AA |
107 | if (len && (start > uwq->msg.arg.pagefault.address || |
108 | start + len <= uwq->msg.arg.pagefault.address)) | |
86039bd3 | 109 | goto out; |
15a77c6f AA |
110 | WRITE_ONCE(uwq->waken, true); |
111 | /* | |
a9668cd6 PZ |
112 | * The Program-Order guarantees provided by the scheduler |
113 | * ensure uwq->waken is visible before the task is woken. | |
15a77c6f | 114 | */ |
86039bd3 | 115 | ret = wake_up_state(wq->private, mode); |
a9668cd6 | 116 | if (ret) { |
86039bd3 AA |
117 | /* |
118 | * Wake only once, autoremove behavior. | |
119 | * | |
a9668cd6 PZ |
120 | * After the effect of list_del_init is visible to the other |
121 | * CPUs, the waitqueue may disappear from under us, see the | |
122 | * !list_empty_careful() in handle_userfault(). | |
123 | * | |
124 | * try_to_wake_up() has an implicit smp_mb(), and the | |
125 | * wq->private is read before calling the extern function | |
126 | * "wake_up_state" (which in turns calls try_to_wake_up). | |
86039bd3 | 127 | */ |
2055da97 | 128 | list_del_init(&wq->entry); |
a9668cd6 | 129 | } |
86039bd3 AA |
130 | out: |
131 | return ret; | |
132 | } | |
133 | ||
134 | /** | |
135 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd | |
136 | * context. | |
137 | * @ctx: [in] Pointer to the userfaultfd context. | |
86039bd3 AA |
138 | */ |
139 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) | |
140 | { | |
141 | if (!atomic_inc_not_zero(&ctx->refcount)) | |
142 | BUG(); | |
143 | } | |
144 | ||
145 | /** | |
146 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd | |
147 | * context. | |
148 | * @ctx: [in] Pointer to userfaultfd context. | |
149 | * | |
150 | * The userfaultfd context reference must have been previously acquired either | |
151 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). | |
152 | */ | |
153 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) | |
154 | { | |
155 | if (atomic_dec_and_test(&ctx->refcount)) { | |
156 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); | |
157 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); | |
158 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); | |
159 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); | |
9cd75c3c PE |
160 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
161 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); | |
86039bd3 AA |
162 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
163 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); | |
d2005e3f | 164 | mmdrop(ctx->mm); |
3004ec9c | 165 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
86039bd3 AA |
166 | } |
167 | } | |
168 | ||
a9b85f94 | 169 | static inline void msg_init(struct uffd_msg *msg) |
86039bd3 | 170 | { |
a9b85f94 AA |
171 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
172 | /* | |
173 | * Must use memset to zero out the paddings or kernel data is | |
174 | * leaked to userland. | |
175 | */ | |
176 | memset(msg, 0, sizeof(struct uffd_msg)); | |
177 | } | |
178 | ||
179 | static inline struct uffd_msg userfault_msg(unsigned long address, | |
180 | unsigned int flags, | |
9d4ac934 AP |
181 | unsigned long reason, |
182 | unsigned int features) | |
a9b85f94 AA |
183 | { |
184 | struct uffd_msg msg; | |
185 | msg_init(&msg); | |
186 | msg.event = UFFD_EVENT_PAGEFAULT; | |
187 | msg.arg.pagefault.address = address; | |
86039bd3 AA |
188 | if (flags & FAULT_FLAG_WRITE) |
189 | /* | |
a4605a61 | 190 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
a9b85f94 AA |
191 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
192 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it | |
193 | * was a read fault, otherwise if set it means it's | |
194 | * a write fault. | |
86039bd3 | 195 | */ |
a9b85f94 | 196 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
86039bd3 AA |
197 | if (reason & VM_UFFD_WP) |
198 | /* | |
a9b85f94 AA |
199 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
200 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was | |
201 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was | |
202 | * a missing fault, otherwise if set it means it's a | |
203 | * write protect fault. | |
86039bd3 | 204 | */ |
a9b85f94 | 205 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
9d4ac934 | 206 | if (features & UFFD_FEATURE_THREAD_ID) |
a36985d3 | 207 | msg.arg.pagefault.feat.ptid = task_pid_vnr(current); |
a9b85f94 | 208 | return msg; |
86039bd3 AA |
209 | } |
210 | ||
369cd212 MK |
211 | #ifdef CONFIG_HUGETLB_PAGE |
212 | /* | |
213 | * Same functionality as userfaultfd_must_wait below with modifications for | |
214 | * hugepmd ranges. | |
215 | */ | |
216 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 217 | struct vm_area_struct *vma, |
369cd212 MK |
218 | unsigned long address, |
219 | unsigned long flags, | |
220 | unsigned long reason) | |
221 | { | |
222 | struct mm_struct *mm = ctx->mm; | |
223 | pte_t *pte; | |
224 | bool ret = true; | |
225 | ||
226 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
227 | ||
7868a208 | 228 | pte = huge_pte_offset(mm, address, vma_mmu_pagesize(vma)); |
369cd212 MK |
229 | if (!pte) |
230 | goto out; | |
231 | ||
232 | ret = false; | |
233 | ||
234 | /* | |
235 | * Lockless access: we're in a wait_event so it's ok if it | |
236 | * changes under us. | |
237 | */ | |
238 | if (huge_pte_none(*pte)) | |
239 | ret = true; | |
240 | if (!huge_pte_write(*pte) && (reason & VM_UFFD_WP)) | |
241 | ret = true; | |
242 | out: | |
243 | return ret; | |
244 | } | |
245 | #else | |
246 | static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx, | |
7868a208 | 247 | struct vm_area_struct *vma, |
369cd212 MK |
248 | unsigned long address, |
249 | unsigned long flags, | |
250 | unsigned long reason) | |
251 | { | |
252 | return false; /* should never get here */ | |
253 | } | |
254 | #endif /* CONFIG_HUGETLB_PAGE */ | |
255 | ||
8d2afd96 AA |
256 | /* |
257 | * Verify the pagetables are still not ok after having reigstered into | |
258 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any | |
259 | * userfault that has already been resolved, if userfaultfd_read and | |
260 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different | |
261 | * threads. | |
262 | */ | |
263 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, | |
264 | unsigned long address, | |
265 | unsigned long flags, | |
266 | unsigned long reason) | |
267 | { | |
268 | struct mm_struct *mm = ctx->mm; | |
269 | pgd_t *pgd; | |
c2febafc | 270 | p4d_t *p4d; |
8d2afd96 AA |
271 | pud_t *pud; |
272 | pmd_t *pmd, _pmd; | |
273 | pte_t *pte; | |
274 | bool ret = true; | |
275 | ||
276 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
277 | ||
278 | pgd = pgd_offset(mm, address); | |
279 | if (!pgd_present(*pgd)) | |
280 | goto out; | |
c2febafc KS |
281 | p4d = p4d_offset(pgd, address); |
282 | if (!p4d_present(*p4d)) | |
283 | goto out; | |
284 | pud = pud_offset(p4d, address); | |
8d2afd96 AA |
285 | if (!pud_present(*pud)) |
286 | goto out; | |
287 | pmd = pmd_offset(pud, address); | |
288 | /* | |
289 | * READ_ONCE must function as a barrier with narrower scope | |
290 | * and it must be equivalent to: | |
291 | * _pmd = *pmd; barrier(); | |
292 | * | |
293 | * This is to deal with the instability (as in | |
294 | * pmd_trans_unstable) of the pmd. | |
295 | */ | |
296 | _pmd = READ_ONCE(*pmd); | |
297 | if (!pmd_present(_pmd)) | |
298 | goto out; | |
299 | ||
300 | ret = false; | |
301 | if (pmd_trans_huge(_pmd)) | |
302 | goto out; | |
303 | ||
304 | /* | |
305 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it | |
306 | * and use the standard pte_offset_map() instead of parsing _pmd. | |
307 | */ | |
308 | pte = pte_offset_map(pmd, address); | |
309 | /* | |
310 | * Lockless access: we're in a wait_event so it's ok if it | |
311 | * changes under us. | |
312 | */ | |
313 | if (pte_none(*pte)) | |
314 | ret = true; | |
315 | pte_unmap(pte); | |
316 | ||
317 | out: | |
318 | return ret; | |
319 | } | |
320 | ||
86039bd3 AA |
321 | /* |
322 | * The locking rules involved in returning VM_FAULT_RETRY depending on | |
323 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and | |
324 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" | |
325 | * recommendation in __lock_page_or_retry is not an understatement. | |
326 | * | |
327 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released | |
328 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is | |
329 | * not set. | |
330 | * | |
331 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not | |
332 | * set, VM_FAULT_RETRY can still be returned if and only if there are | |
333 | * fatal_signal_pending()s, and the mmap_sem must be released before | |
334 | * returning it. | |
335 | */ | |
82b0f8c3 | 336 | int handle_userfault(struct vm_fault *vmf, unsigned long reason) |
86039bd3 | 337 | { |
82b0f8c3 | 338 | struct mm_struct *mm = vmf->vma->vm_mm; |
86039bd3 AA |
339 | struct userfaultfd_ctx *ctx; |
340 | struct userfaultfd_wait_queue uwq; | |
ba85c702 | 341 | int ret; |
dfa37dc3 | 342 | bool must_wait, return_to_userland; |
15a77c6f | 343 | long blocking_state; |
86039bd3 | 344 | |
ba85c702 | 345 | ret = VM_FAULT_SIGBUS; |
64c2b203 AA |
346 | |
347 | /* | |
348 | * We don't do userfault handling for the final child pid update. | |
349 | * | |
350 | * We also don't do userfault handling during | |
351 | * coredumping. hugetlbfs has the special | |
352 | * follow_hugetlb_page() to skip missing pages in the | |
353 | * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with | |
354 | * the no_page_table() helper in follow_page_mask(), but the | |
355 | * shmem_vm_ops->fault method is invoked even during | |
356 | * coredumping without mmap_sem and it ends up here. | |
357 | */ | |
358 | if (current->flags & (PF_EXITING|PF_DUMPCORE)) | |
359 | goto out; | |
360 | ||
361 | /* | |
362 | * Coredumping runs without mmap_sem so we can only check that | |
363 | * the mmap_sem is held, if PF_DUMPCORE was not set. | |
364 | */ | |
365 | WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem)); | |
366 | ||
82b0f8c3 | 367 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
86039bd3 | 368 | if (!ctx) |
ba85c702 | 369 | goto out; |
86039bd3 AA |
370 | |
371 | BUG_ON(ctx->mm != mm); | |
372 | ||
373 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); | |
374 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); | |
375 | ||
2d6d6f5a PS |
376 | if (ctx->features & UFFD_FEATURE_SIGBUS) |
377 | goto out; | |
378 | ||
86039bd3 AA |
379 | /* |
380 | * If it's already released don't get it. This avoids to loop | |
381 | * in __get_user_pages if userfaultfd_release waits on the | |
382 | * caller of handle_userfault to release the mmap_sem. | |
383 | */ | |
384 | if (unlikely(ACCESS_ONCE(ctx->released))) | |
ba85c702 | 385 | goto out; |
86039bd3 AA |
386 | |
387 | /* | |
388 | * Check that we can return VM_FAULT_RETRY. | |
389 | * | |
390 | * NOTE: it should become possible to return VM_FAULT_RETRY | |
391 | * even if FAULT_FLAG_TRIED is set without leading to gup() | |
392 | * -EBUSY failures, if the userfaultfd is to be extended for | |
393 | * VM_UFFD_WP tracking and we intend to arm the userfault | |
394 | * without first stopping userland access to the memory. For | |
395 | * VM_UFFD_MISSING userfaults this is enough for now. | |
396 | */ | |
82b0f8c3 | 397 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
86039bd3 AA |
398 | /* |
399 | * Validate the invariant that nowait must allow retry | |
400 | * to be sure not to return SIGBUS erroneously on | |
401 | * nowait invocations. | |
402 | */ | |
82b0f8c3 | 403 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
86039bd3 AA |
404 | #ifdef CONFIG_DEBUG_VM |
405 | if (printk_ratelimit()) { | |
406 | printk(KERN_WARNING | |
82b0f8c3 JK |
407 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
408 | vmf->flags); | |
86039bd3 AA |
409 | dump_stack(); |
410 | } | |
411 | #endif | |
ba85c702 | 412 | goto out; |
86039bd3 AA |
413 | } |
414 | ||
415 | /* | |
416 | * Handle nowait, not much to do other than tell it to retry | |
417 | * and wait. | |
418 | */ | |
ba85c702 | 419 | ret = VM_FAULT_RETRY; |
82b0f8c3 | 420 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
ba85c702 | 421 | goto out; |
86039bd3 AA |
422 | |
423 | /* take the reference before dropping the mmap_sem */ | |
424 | userfaultfd_ctx_get(ctx); | |
425 | ||
86039bd3 AA |
426 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
427 | uwq.wq.private = current; | |
9d4ac934 AP |
428 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason, |
429 | ctx->features); | |
86039bd3 | 430 | uwq.ctx = ctx; |
15a77c6f | 431 | uwq.waken = false; |
86039bd3 | 432 | |
bae473a4 | 433 | return_to_userland = |
82b0f8c3 | 434 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
dfa37dc3 | 435 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
15a77c6f AA |
436 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
437 | TASK_KILLABLE; | |
dfa37dc3 | 438 | |
15b726ef | 439 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
440 | /* |
441 | * After the __add_wait_queue the uwq is visible to userland | |
442 | * through poll/read(). | |
443 | */ | |
15b726ef AA |
444 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
445 | /* | |
446 | * The smp_mb() after __set_current_state prevents the reads | |
447 | * following the spin_unlock to happen before the list_add in | |
448 | * __add_wait_queue. | |
449 | */ | |
15a77c6f | 450 | set_current_state(blocking_state); |
15b726ef | 451 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 452 | |
369cd212 MK |
453 | if (!is_vm_hugetlb_page(vmf->vma)) |
454 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, | |
455 | reason); | |
456 | else | |
7868a208 PA |
457 | must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma, |
458 | vmf->address, | |
369cd212 | 459 | vmf->flags, reason); |
8d2afd96 AA |
460 | up_read(&mm->mmap_sem); |
461 | ||
462 | if (likely(must_wait && !ACCESS_ONCE(ctx->released) && | |
dfa37dc3 AA |
463 | (return_to_userland ? !signal_pending(current) : |
464 | !fatal_signal_pending(current)))) { | |
86039bd3 AA |
465 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
466 | schedule(); | |
ba85c702 | 467 | ret |= VM_FAULT_MAJOR; |
15a77c6f AA |
468 | |
469 | /* | |
470 | * False wakeups can orginate even from rwsem before | |
471 | * up_read() however userfaults will wait either for a | |
472 | * targeted wakeup on the specific uwq waitqueue from | |
473 | * wake_userfault() or for signals or for uffd | |
474 | * release. | |
475 | */ | |
476 | while (!READ_ONCE(uwq.waken)) { | |
477 | /* | |
478 | * This needs the full smp_store_mb() | |
479 | * guarantee as the state write must be | |
480 | * visible to other CPUs before reading | |
481 | * uwq.waken from other CPUs. | |
482 | */ | |
483 | set_current_state(blocking_state); | |
484 | if (READ_ONCE(uwq.waken) || | |
485 | READ_ONCE(ctx->released) || | |
486 | (return_to_userland ? signal_pending(current) : | |
487 | fatal_signal_pending(current))) | |
488 | break; | |
489 | schedule(); | |
490 | } | |
ba85c702 | 491 | } |
86039bd3 | 492 | |
ba85c702 | 493 | __set_current_state(TASK_RUNNING); |
15b726ef | 494 | |
dfa37dc3 AA |
495 | if (return_to_userland) { |
496 | if (signal_pending(current) && | |
497 | !fatal_signal_pending(current)) { | |
498 | /* | |
499 | * If we got a SIGSTOP or SIGCONT and this is | |
500 | * a normal userland page fault, just let | |
501 | * userland return so the signal will be | |
502 | * handled and gdb debugging works. The page | |
503 | * fault code immediately after we return from | |
504 | * this function is going to release the | |
505 | * mmap_sem and it's not depending on it | |
506 | * (unlike gup would if we were not to return | |
507 | * VM_FAULT_RETRY). | |
508 | * | |
509 | * If a fatal signal is pending we still take | |
510 | * the streamlined VM_FAULT_RETRY failure path | |
511 | * and there's no need to retake the mmap_sem | |
512 | * in such case. | |
513 | */ | |
514 | down_read(&mm->mmap_sem); | |
6bbc4a41 | 515 | ret = VM_FAULT_NOPAGE; |
dfa37dc3 AA |
516 | } |
517 | } | |
518 | ||
15b726ef AA |
519 | /* |
520 | * Here we race with the list_del; list_add in | |
521 | * userfaultfd_ctx_read(), however because we don't ever run | |
522 | * list_del_init() to refile across the two lists, the prev | |
523 | * and next pointers will never point to self. list_add also | |
524 | * would never let any of the two pointers to point to | |
525 | * self. So list_empty_careful won't risk to see both pointers | |
526 | * pointing to self at any time during the list refile. The | |
527 | * only case where list_del_init() is called is the full | |
528 | * removal in the wake function and there we don't re-list_add | |
529 | * and it's fine not to block on the spinlock. The uwq on this | |
530 | * kernel stack can be released after the list_del_init. | |
531 | */ | |
2055da97 | 532 | if (!list_empty_careful(&uwq.wq.entry)) { |
15b726ef AA |
533 | spin_lock(&ctx->fault_pending_wqh.lock); |
534 | /* | |
535 | * No need of list_del_init(), the uwq on the stack | |
536 | * will be freed shortly anyway. | |
537 | */ | |
2055da97 | 538 | list_del(&uwq.wq.entry); |
15b726ef | 539 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 540 | } |
86039bd3 AA |
541 | |
542 | /* | |
543 | * ctx may go away after this if the userfault pseudo fd is | |
544 | * already released. | |
545 | */ | |
546 | userfaultfd_ctx_put(ctx); | |
547 | ||
ba85c702 AA |
548 | out: |
549 | return ret; | |
86039bd3 AA |
550 | } |
551 | ||
8c9e7bb7 AA |
552 | static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
553 | struct userfaultfd_wait_queue *ewq) | |
9cd75c3c | 554 | { |
9a69a829 AA |
555 | if (WARN_ON_ONCE(current->flags & PF_EXITING)) |
556 | goto out; | |
9cd75c3c PE |
557 | |
558 | ewq->ctx = ctx; | |
559 | init_waitqueue_entry(&ewq->wq, current); | |
560 | ||
561 | spin_lock(&ctx->event_wqh.lock); | |
562 | /* | |
563 | * After the __add_wait_queue the uwq is visible to userland | |
564 | * through poll/read(). | |
565 | */ | |
566 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); | |
567 | for (;;) { | |
568 | set_current_state(TASK_KILLABLE); | |
569 | if (ewq->msg.event == 0) | |
570 | break; | |
571 | if (ACCESS_ONCE(ctx->released) || | |
572 | fatal_signal_pending(current)) { | |
9cd75c3c | 573 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); |
7eb76d45 MR |
574 | if (ewq->msg.event == UFFD_EVENT_FORK) { |
575 | struct userfaultfd_ctx *new; | |
576 | ||
577 | new = (struct userfaultfd_ctx *) | |
578 | (unsigned long) | |
579 | ewq->msg.arg.reserved.reserved1; | |
580 | ||
581 | userfaultfd_ctx_put(new); | |
582 | } | |
9cd75c3c PE |
583 | break; |
584 | } | |
585 | ||
586 | spin_unlock(&ctx->event_wqh.lock); | |
587 | ||
588 | wake_up_poll(&ctx->fd_wqh, POLLIN); | |
589 | schedule(); | |
590 | ||
591 | spin_lock(&ctx->event_wqh.lock); | |
592 | } | |
593 | __set_current_state(TASK_RUNNING); | |
594 | spin_unlock(&ctx->event_wqh.lock); | |
595 | ||
596 | /* | |
597 | * ctx may go away after this if the userfault pseudo fd is | |
598 | * already released. | |
599 | */ | |
9a69a829 | 600 | out: |
9cd75c3c | 601 | userfaultfd_ctx_put(ctx); |
9cd75c3c PE |
602 | } |
603 | ||
604 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, | |
605 | struct userfaultfd_wait_queue *ewq) | |
606 | { | |
607 | ewq->msg.event = 0; | |
608 | wake_up_locked(&ctx->event_wqh); | |
609 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
610 | } | |
611 | ||
893e26e6 PE |
612 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
613 | { | |
614 | struct userfaultfd_ctx *ctx = NULL, *octx; | |
615 | struct userfaultfd_fork_ctx *fctx; | |
616 | ||
617 | octx = vma->vm_userfaultfd_ctx.ctx; | |
618 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { | |
619 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
620 | vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); | |
621 | return 0; | |
622 | } | |
623 | ||
624 | list_for_each_entry(fctx, fcs, list) | |
625 | if (fctx->orig == octx) { | |
626 | ctx = fctx->new; | |
627 | break; | |
628 | } | |
629 | ||
630 | if (!ctx) { | |
631 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); | |
632 | if (!fctx) | |
633 | return -ENOMEM; | |
634 | ||
635 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); | |
636 | if (!ctx) { | |
637 | kfree(fctx); | |
638 | return -ENOMEM; | |
639 | } | |
640 | ||
641 | atomic_set(&ctx->refcount, 1); | |
642 | ctx->flags = octx->flags; | |
643 | ctx->state = UFFD_STATE_RUNNING; | |
644 | ctx->features = octx->features; | |
645 | ctx->released = false; | |
646 | ctx->mm = vma->vm_mm; | |
d3aadc8e | 647 | atomic_inc(&ctx->mm->mm_count); |
893e26e6 PE |
648 | |
649 | userfaultfd_ctx_get(octx); | |
650 | fctx->orig = octx; | |
651 | fctx->new = ctx; | |
652 | list_add_tail(&fctx->list, fcs); | |
653 | } | |
654 | ||
655 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
656 | return 0; | |
657 | } | |
658 | ||
8c9e7bb7 | 659 | static void dup_fctx(struct userfaultfd_fork_ctx *fctx) |
893e26e6 PE |
660 | { |
661 | struct userfaultfd_ctx *ctx = fctx->orig; | |
662 | struct userfaultfd_wait_queue ewq; | |
663 | ||
664 | msg_init(&ewq.msg); | |
665 | ||
666 | ewq.msg.event = UFFD_EVENT_FORK; | |
667 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; | |
668 | ||
8c9e7bb7 | 669 | userfaultfd_event_wait_completion(ctx, &ewq); |
893e26e6 PE |
670 | } |
671 | ||
672 | void dup_userfaultfd_complete(struct list_head *fcs) | |
673 | { | |
893e26e6 PE |
674 | struct userfaultfd_fork_ctx *fctx, *n; |
675 | ||
676 | list_for_each_entry_safe(fctx, n, fcs, list) { | |
8c9e7bb7 | 677 | dup_fctx(fctx); |
893e26e6 PE |
678 | list_del(&fctx->list); |
679 | kfree(fctx); | |
680 | } | |
681 | } | |
682 | ||
72f87654 PE |
683 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
684 | struct vm_userfaultfd_ctx *vm_ctx) | |
685 | { | |
686 | struct userfaultfd_ctx *ctx; | |
687 | ||
688 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
689 | if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) { | |
690 | vm_ctx->ctx = ctx; | |
691 | userfaultfd_ctx_get(ctx); | |
692 | } | |
693 | } | |
694 | ||
90794bf1 | 695 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
72f87654 PE |
696 | unsigned long from, unsigned long to, |
697 | unsigned long len) | |
698 | { | |
90794bf1 | 699 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
72f87654 PE |
700 | struct userfaultfd_wait_queue ewq; |
701 | ||
702 | if (!ctx) | |
703 | return; | |
704 | ||
705 | if (to & ~PAGE_MASK) { | |
706 | userfaultfd_ctx_put(ctx); | |
707 | return; | |
708 | } | |
709 | ||
710 | msg_init(&ewq.msg); | |
711 | ||
712 | ewq.msg.event = UFFD_EVENT_REMAP; | |
713 | ewq.msg.arg.remap.from = from; | |
714 | ewq.msg.arg.remap.to = to; | |
715 | ewq.msg.arg.remap.len = len; | |
716 | ||
717 | userfaultfd_event_wait_completion(ctx, &ewq); | |
718 | } | |
719 | ||
70ccb92f | 720 | bool userfaultfd_remove(struct vm_area_struct *vma, |
d811914d | 721 | unsigned long start, unsigned long end) |
05ce7724 PE |
722 | { |
723 | struct mm_struct *mm = vma->vm_mm; | |
724 | struct userfaultfd_ctx *ctx; | |
725 | struct userfaultfd_wait_queue ewq; | |
726 | ||
727 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
d811914d | 728 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE)) |
70ccb92f | 729 | return true; |
05ce7724 PE |
730 | |
731 | userfaultfd_ctx_get(ctx); | |
732 | up_read(&mm->mmap_sem); | |
733 | ||
05ce7724 PE |
734 | msg_init(&ewq.msg); |
735 | ||
d811914d MR |
736 | ewq.msg.event = UFFD_EVENT_REMOVE; |
737 | ewq.msg.arg.remove.start = start; | |
738 | ewq.msg.arg.remove.end = end; | |
05ce7724 PE |
739 | |
740 | userfaultfd_event_wait_completion(ctx, &ewq); | |
741 | ||
70ccb92f | 742 | return false; |
05ce7724 PE |
743 | } |
744 | ||
897ab3e0 MR |
745 | static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps, |
746 | unsigned long start, unsigned long end) | |
747 | { | |
748 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
749 | ||
750 | list_for_each_entry(unmap_ctx, unmaps, list) | |
751 | if (unmap_ctx->ctx == ctx && unmap_ctx->start == start && | |
752 | unmap_ctx->end == end) | |
753 | return true; | |
754 | ||
755 | return false; | |
756 | } | |
757 | ||
758 | int userfaultfd_unmap_prep(struct vm_area_struct *vma, | |
759 | unsigned long start, unsigned long end, | |
760 | struct list_head *unmaps) | |
761 | { | |
762 | for ( ; vma && vma->vm_start < end; vma = vma->vm_next) { | |
763 | struct userfaultfd_unmap_ctx *unmap_ctx; | |
764 | struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx; | |
765 | ||
766 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) || | |
767 | has_unmap_ctx(ctx, unmaps, start, end)) | |
768 | continue; | |
769 | ||
770 | unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL); | |
771 | if (!unmap_ctx) | |
772 | return -ENOMEM; | |
773 | ||
774 | userfaultfd_ctx_get(ctx); | |
775 | unmap_ctx->ctx = ctx; | |
776 | unmap_ctx->start = start; | |
777 | unmap_ctx->end = end; | |
778 | list_add_tail(&unmap_ctx->list, unmaps); | |
779 | } | |
780 | ||
781 | return 0; | |
782 | } | |
783 | ||
784 | void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf) | |
785 | { | |
786 | struct userfaultfd_unmap_ctx *ctx, *n; | |
787 | struct userfaultfd_wait_queue ewq; | |
788 | ||
789 | list_for_each_entry_safe(ctx, n, uf, list) { | |
790 | msg_init(&ewq.msg); | |
791 | ||
792 | ewq.msg.event = UFFD_EVENT_UNMAP; | |
793 | ewq.msg.arg.remove.start = ctx->start; | |
794 | ewq.msg.arg.remove.end = ctx->end; | |
795 | ||
796 | userfaultfd_event_wait_completion(ctx->ctx, &ewq); | |
797 | ||
798 | list_del(&ctx->list); | |
799 | kfree(ctx); | |
800 | } | |
801 | } | |
802 | ||
86039bd3 AA |
803 | static int userfaultfd_release(struct inode *inode, struct file *file) |
804 | { | |
805 | struct userfaultfd_ctx *ctx = file->private_data; | |
806 | struct mm_struct *mm = ctx->mm; | |
807 | struct vm_area_struct *vma, *prev; | |
808 | /* len == 0 means wake all */ | |
809 | struct userfaultfd_wake_range range = { .len = 0, }; | |
810 | unsigned long new_flags; | |
811 | ||
812 | ACCESS_ONCE(ctx->released) = true; | |
813 | ||
d2005e3f ON |
814 | if (!mmget_not_zero(mm)) |
815 | goto wakeup; | |
816 | ||
86039bd3 AA |
817 | /* |
818 | * Flush page faults out of all CPUs. NOTE: all page faults | |
819 | * must be retried without returning VM_FAULT_SIGBUS if | |
820 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx | |
821 | * changes while handle_userfault released the mmap_sem. So | |
822 | * it's critical that released is set to true (above), before | |
823 | * taking the mmap_sem for writing. | |
824 | */ | |
825 | down_write(&mm->mmap_sem); | |
826 | prev = NULL; | |
827 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
828 | cond_resched(); | |
829 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ | |
830 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
831 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { | |
832 | prev = vma; | |
833 | continue; | |
834 | } | |
835 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); | |
836 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, | |
837 | new_flags, vma->anon_vma, | |
838 | vma->vm_file, vma->vm_pgoff, | |
839 | vma_policy(vma), | |
840 | NULL_VM_UFFD_CTX); | |
841 | if (prev) | |
842 | vma = prev; | |
843 | else | |
844 | prev = vma; | |
845 | vma->vm_flags = new_flags; | |
846 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
847 | } | |
848 | up_write(&mm->mmap_sem); | |
d2005e3f ON |
849 | mmput(mm); |
850 | wakeup: | |
86039bd3 | 851 | /* |
15b726ef | 852 | * After no new page faults can wait on this fault_*wqh, flush |
86039bd3 | 853 | * the last page faults that may have been already waiting on |
15b726ef | 854 | * the fault_*wqh. |
86039bd3 | 855 | */ |
15b726ef | 856 | spin_lock(&ctx->fault_pending_wqh.lock); |
ac5be6b4 AA |
857 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
858 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); | |
15b726ef | 859 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 860 | |
5a18b64e MR |
861 | /* Flush pending events that may still wait on event_wqh */ |
862 | wake_up_all(&ctx->event_wqh); | |
863 | ||
86039bd3 AA |
864 | wake_up_poll(&ctx->fd_wqh, POLLHUP); |
865 | userfaultfd_ctx_put(ctx); | |
866 | return 0; | |
867 | } | |
868 | ||
15b726ef | 869 | /* fault_pending_wqh.lock must be hold by the caller */ |
6dcc27fd PE |
870 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
871 | wait_queue_head_t *wqh) | |
86039bd3 | 872 | { |
ac6424b9 | 873 | wait_queue_entry_t *wq; |
15b726ef | 874 | struct userfaultfd_wait_queue *uwq; |
86039bd3 | 875 | |
6dcc27fd | 876 | VM_BUG_ON(!spin_is_locked(&wqh->lock)); |
86039bd3 | 877 | |
15b726ef | 878 | uwq = NULL; |
6dcc27fd | 879 | if (!waitqueue_active(wqh)) |
15b726ef AA |
880 | goto out; |
881 | /* walk in reverse to provide FIFO behavior to read userfaults */ | |
2055da97 | 882 | wq = list_last_entry(&wqh->head, typeof(*wq), entry); |
15b726ef AA |
883 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
884 | out: | |
885 | return uwq; | |
86039bd3 | 886 | } |
6dcc27fd PE |
887 | |
888 | static inline struct userfaultfd_wait_queue *find_userfault( | |
889 | struct userfaultfd_ctx *ctx) | |
890 | { | |
891 | return find_userfault_in(&ctx->fault_pending_wqh); | |
892 | } | |
86039bd3 | 893 | |
9cd75c3c PE |
894 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
895 | struct userfaultfd_ctx *ctx) | |
896 | { | |
897 | return find_userfault_in(&ctx->event_wqh); | |
898 | } | |
899 | ||
86039bd3 AA |
900 | static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) |
901 | { | |
902 | struct userfaultfd_ctx *ctx = file->private_data; | |
903 | unsigned int ret; | |
904 | ||
905 | poll_wait(file, &ctx->fd_wqh, wait); | |
906 | ||
907 | switch (ctx->state) { | |
908 | case UFFD_STATE_WAIT_API: | |
909 | return POLLERR; | |
910 | case UFFD_STATE_RUNNING: | |
ba85c702 AA |
911 | /* |
912 | * poll() never guarantees that read won't block. | |
913 | * userfaults can be waken before they're read(). | |
914 | */ | |
915 | if (unlikely(!(file->f_flags & O_NONBLOCK))) | |
916 | return POLLERR; | |
15b726ef AA |
917 | /* |
918 | * lockless access to see if there are pending faults | |
919 | * __pollwait last action is the add_wait_queue but | |
920 | * the spin_unlock would allow the waitqueue_active to | |
921 | * pass above the actual list_add inside | |
922 | * add_wait_queue critical section. So use a full | |
923 | * memory barrier to serialize the list_add write of | |
924 | * add_wait_queue() with the waitqueue_active read | |
925 | * below. | |
926 | */ | |
927 | ret = 0; | |
928 | smp_mb(); | |
929 | if (waitqueue_active(&ctx->fault_pending_wqh)) | |
930 | ret = POLLIN; | |
9cd75c3c PE |
931 | else if (waitqueue_active(&ctx->event_wqh)) |
932 | ret = POLLIN; | |
933 | ||
86039bd3 AA |
934 | return ret; |
935 | default: | |
8474901a AA |
936 | WARN_ON_ONCE(1); |
937 | return POLLERR; | |
86039bd3 AA |
938 | } |
939 | } | |
940 | ||
893e26e6 PE |
941 | static const struct file_operations userfaultfd_fops; |
942 | ||
943 | static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, | |
944 | struct userfaultfd_ctx *new, | |
945 | struct uffd_msg *msg) | |
946 | { | |
947 | int fd; | |
948 | struct file *file; | |
949 | unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS; | |
950 | ||
951 | fd = get_unused_fd_flags(flags); | |
952 | if (fd < 0) | |
953 | return fd; | |
954 | ||
955 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new, | |
956 | O_RDWR | flags); | |
957 | if (IS_ERR(file)) { | |
958 | put_unused_fd(fd); | |
959 | return PTR_ERR(file); | |
960 | } | |
961 | ||
962 | fd_install(fd, file); | |
963 | msg->arg.reserved.reserved1 = 0; | |
964 | msg->arg.fork.ufd = fd; | |
965 | ||
966 | return 0; | |
967 | } | |
968 | ||
86039bd3 | 969 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
a9b85f94 | 970 | struct uffd_msg *msg) |
86039bd3 AA |
971 | { |
972 | ssize_t ret; | |
973 | DECLARE_WAITQUEUE(wait, current); | |
15b726ef | 974 | struct userfaultfd_wait_queue *uwq; |
893e26e6 PE |
975 | /* |
976 | * Handling fork event requires sleeping operations, so | |
977 | * we drop the event_wqh lock, then do these ops, then | |
978 | * lock it back and wake up the waiter. While the lock is | |
979 | * dropped the ewq may go away so we keep track of it | |
980 | * carefully. | |
981 | */ | |
982 | LIST_HEAD(fork_event); | |
983 | struct userfaultfd_ctx *fork_nctx = NULL; | |
86039bd3 | 984 | |
15b726ef | 985 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
86039bd3 AA |
986 | spin_lock(&ctx->fd_wqh.lock); |
987 | __add_wait_queue(&ctx->fd_wqh, &wait); | |
988 | for (;;) { | |
989 | set_current_state(TASK_INTERRUPTIBLE); | |
15b726ef AA |
990 | spin_lock(&ctx->fault_pending_wqh.lock); |
991 | uwq = find_userfault(ctx); | |
992 | if (uwq) { | |
2c5b7e1b AA |
993 | /* |
994 | * Use a seqcount to repeat the lockless check | |
995 | * in wake_userfault() to avoid missing | |
996 | * wakeups because during the refile both | |
997 | * waitqueue could become empty if this is the | |
998 | * only userfault. | |
999 | */ | |
1000 | write_seqcount_begin(&ctx->refile_seq); | |
1001 | ||
86039bd3 | 1002 | /* |
15b726ef AA |
1003 | * The fault_pending_wqh.lock prevents the uwq |
1004 | * to disappear from under us. | |
1005 | * | |
1006 | * Refile this userfault from | |
1007 | * fault_pending_wqh to fault_wqh, it's not | |
1008 | * pending anymore after we read it. | |
1009 | * | |
1010 | * Use list_del() by hand (as | |
1011 | * userfaultfd_wake_function also uses | |
1012 | * list_del_init() by hand) to be sure nobody | |
1013 | * changes __remove_wait_queue() to use | |
1014 | * list_del_init() in turn breaking the | |
1015 | * !list_empty_careful() check in | |
2055da97 | 1016 | * handle_userfault(). The uwq->wq.head list |
15b726ef AA |
1017 | * must never be empty at any time during the |
1018 | * refile, or the waitqueue could disappear | |
1019 | * from under us. The "wait_queue_head_t" | |
1020 | * parameter of __remove_wait_queue() is unused | |
1021 | * anyway. | |
86039bd3 | 1022 | */ |
2055da97 | 1023 | list_del(&uwq->wq.entry); |
15b726ef AA |
1024 | __add_wait_queue(&ctx->fault_wqh, &uwq->wq); |
1025 | ||
2c5b7e1b AA |
1026 | write_seqcount_end(&ctx->refile_seq); |
1027 | ||
a9b85f94 AA |
1028 | /* careful to always initialize msg if ret == 0 */ |
1029 | *msg = uwq->msg; | |
15b726ef | 1030 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1031 | ret = 0; |
1032 | break; | |
1033 | } | |
15b726ef | 1034 | spin_unlock(&ctx->fault_pending_wqh.lock); |
9cd75c3c PE |
1035 | |
1036 | spin_lock(&ctx->event_wqh.lock); | |
1037 | uwq = find_userfault_evt(ctx); | |
1038 | if (uwq) { | |
1039 | *msg = uwq->msg; | |
1040 | ||
893e26e6 PE |
1041 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
1042 | fork_nctx = (struct userfaultfd_ctx *) | |
1043 | (unsigned long) | |
1044 | uwq->msg.arg.reserved.reserved1; | |
2055da97 | 1045 | list_move(&uwq->wq.entry, &fork_event); |
893e26e6 PE |
1046 | spin_unlock(&ctx->event_wqh.lock); |
1047 | ret = 0; | |
1048 | break; | |
1049 | } | |
1050 | ||
9cd75c3c PE |
1051 | userfaultfd_event_complete(ctx, uwq); |
1052 | spin_unlock(&ctx->event_wqh.lock); | |
1053 | ret = 0; | |
1054 | break; | |
1055 | } | |
1056 | spin_unlock(&ctx->event_wqh.lock); | |
1057 | ||
86039bd3 AA |
1058 | if (signal_pending(current)) { |
1059 | ret = -ERESTARTSYS; | |
1060 | break; | |
1061 | } | |
1062 | if (no_wait) { | |
1063 | ret = -EAGAIN; | |
1064 | break; | |
1065 | } | |
1066 | spin_unlock(&ctx->fd_wqh.lock); | |
1067 | schedule(); | |
1068 | spin_lock(&ctx->fd_wqh.lock); | |
1069 | } | |
1070 | __remove_wait_queue(&ctx->fd_wqh, &wait); | |
1071 | __set_current_state(TASK_RUNNING); | |
1072 | spin_unlock(&ctx->fd_wqh.lock); | |
1073 | ||
893e26e6 PE |
1074 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
1075 | ret = resolve_userfault_fork(ctx, fork_nctx, msg); | |
1076 | ||
1077 | if (!ret) { | |
1078 | spin_lock(&ctx->event_wqh.lock); | |
1079 | if (!list_empty(&fork_event)) { | |
1080 | uwq = list_first_entry(&fork_event, | |
1081 | typeof(*uwq), | |
2055da97 IM |
1082 | wq.entry); |
1083 | list_del(&uwq->wq.entry); | |
893e26e6 PE |
1084 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); |
1085 | userfaultfd_event_complete(ctx, uwq); | |
1086 | } | |
1087 | spin_unlock(&ctx->event_wqh.lock); | |
1088 | } | |
1089 | } | |
1090 | ||
86039bd3 AA |
1091 | return ret; |
1092 | } | |
1093 | ||
1094 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, | |
1095 | size_t count, loff_t *ppos) | |
1096 | { | |
1097 | struct userfaultfd_ctx *ctx = file->private_data; | |
1098 | ssize_t _ret, ret = 0; | |
a9b85f94 | 1099 | struct uffd_msg msg; |
86039bd3 AA |
1100 | int no_wait = file->f_flags & O_NONBLOCK; |
1101 | ||
1102 | if (ctx->state == UFFD_STATE_WAIT_API) | |
1103 | return -EINVAL; | |
86039bd3 AA |
1104 | |
1105 | for (;;) { | |
a9b85f94 | 1106 | if (count < sizeof(msg)) |
86039bd3 | 1107 | return ret ? ret : -EINVAL; |
a9b85f94 | 1108 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
86039bd3 AA |
1109 | if (_ret < 0) |
1110 | return ret ? ret : _ret; | |
a9b85f94 | 1111 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
86039bd3 | 1112 | return ret ? ret : -EFAULT; |
a9b85f94 AA |
1113 | ret += sizeof(msg); |
1114 | buf += sizeof(msg); | |
1115 | count -= sizeof(msg); | |
86039bd3 AA |
1116 | /* |
1117 | * Allow to read more than one fault at time but only | |
1118 | * block if waiting for the very first one. | |
1119 | */ | |
1120 | no_wait = O_NONBLOCK; | |
1121 | } | |
1122 | } | |
1123 | ||
1124 | static void __wake_userfault(struct userfaultfd_ctx *ctx, | |
1125 | struct userfaultfd_wake_range *range) | |
1126 | { | |
15b726ef | 1127 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 1128 | /* wake all in the range and autoremove */ |
15b726ef | 1129 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
ac5be6b4 | 1130 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
15b726ef AA |
1131 | range); |
1132 | if (waitqueue_active(&ctx->fault_wqh)) | |
ac5be6b4 | 1133 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); |
15b726ef | 1134 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1135 | } |
1136 | ||
1137 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, | |
1138 | struct userfaultfd_wake_range *range) | |
1139 | { | |
2c5b7e1b AA |
1140 | unsigned seq; |
1141 | bool need_wakeup; | |
1142 | ||
86039bd3 AA |
1143 | /* |
1144 | * To be sure waitqueue_active() is not reordered by the CPU | |
1145 | * before the pagetable update, use an explicit SMP memory | |
1146 | * barrier here. PT lock release or up_read(mmap_sem) still | |
1147 | * have release semantics that can allow the | |
1148 | * waitqueue_active() to be reordered before the pte update. | |
1149 | */ | |
1150 | smp_mb(); | |
1151 | ||
1152 | /* | |
1153 | * Use waitqueue_active because it's very frequent to | |
1154 | * change the address space atomically even if there are no | |
1155 | * userfaults yet. So we take the spinlock only when we're | |
1156 | * sure we've userfaults to wake. | |
1157 | */ | |
2c5b7e1b AA |
1158 | do { |
1159 | seq = read_seqcount_begin(&ctx->refile_seq); | |
1160 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || | |
1161 | waitqueue_active(&ctx->fault_wqh); | |
1162 | cond_resched(); | |
1163 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); | |
1164 | if (need_wakeup) | |
86039bd3 AA |
1165 | __wake_userfault(ctx, range); |
1166 | } | |
1167 | ||
1168 | static __always_inline int validate_range(struct mm_struct *mm, | |
1169 | __u64 start, __u64 len) | |
1170 | { | |
1171 | __u64 task_size = mm->task_size; | |
1172 | ||
1173 | if (start & ~PAGE_MASK) | |
1174 | return -EINVAL; | |
1175 | if (len & ~PAGE_MASK) | |
1176 | return -EINVAL; | |
1177 | if (!len) | |
1178 | return -EINVAL; | |
1179 | if (start < mmap_min_addr) | |
1180 | return -EINVAL; | |
1181 | if (start >= task_size) | |
1182 | return -EINVAL; | |
1183 | if (len > task_size - start) | |
1184 | return -EINVAL; | |
1185 | return 0; | |
1186 | } | |
1187 | ||
ba6907db MR |
1188 | static inline bool vma_can_userfault(struct vm_area_struct *vma) |
1189 | { | |
cac67329 MR |
1190 | return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || |
1191 | vma_is_shmem(vma); | |
ba6907db MR |
1192 | } |
1193 | ||
86039bd3 AA |
1194 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, |
1195 | unsigned long arg) | |
1196 | { | |
1197 | struct mm_struct *mm = ctx->mm; | |
1198 | struct vm_area_struct *vma, *prev, *cur; | |
1199 | int ret; | |
1200 | struct uffdio_register uffdio_register; | |
1201 | struct uffdio_register __user *user_uffdio_register; | |
1202 | unsigned long vm_flags, new_flags; | |
1203 | bool found; | |
ce53e8e6 | 1204 | bool basic_ioctls; |
86039bd3 AA |
1205 | unsigned long start, end, vma_end; |
1206 | ||
1207 | user_uffdio_register = (struct uffdio_register __user *) arg; | |
1208 | ||
1209 | ret = -EFAULT; | |
1210 | if (copy_from_user(&uffdio_register, user_uffdio_register, | |
1211 | sizeof(uffdio_register)-sizeof(__u64))) | |
1212 | goto out; | |
1213 | ||
1214 | ret = -EINVAL; | |
1215 | if (!uffdio_register.mode) | |
1216 | goto out; | |
1217 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| | |
1218 | UFFDIO_REGISTER_MODE_WP)) | |
1219 | goto out; | |
1220 | vm_flags = 0; | |
1221 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) | |
1222 | vm_flags |= VM_UFFD_MISSING; | |
1223 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { | |
1224 | vm_flags |= VM_UFFD_WP; | |
1225 | /* | |
1226 | * FIXME: remove the below error constraint by | |
1227 | * implementing the wprotect tracking mode. | |
1228 | */ | |
1229 | ret = -EINVAL; | |
1230 | goto out; | |
1231 | } | |
1232 | ||
1233 | ret = validate_range(mm, uffdio_register.range.start, | |
1234 | uffdio_register.range.len); | |
1235 | if (ret) | |
1236 | goto out; | |
1237 | ||
1238 | start = uffdio_register.range.start; | |
1239 | end = start + uffdio_register.range.len; | |
1240 | ||
d2005e3f ON |
1241 | ret = -ENOMEM; |
1242 | if (!mmget_not_zero(mm)) | |
1243 | goto out; | |
1244 | ||
86039bd3 AA |
1245 | down_write(&mm->mmap_sem); |
1246 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1247 | if (!vma) |
1248 | goto out_unlock; | |
1249 | ||
1250 | /* check that there's at least one vma in the range */ | |
1251 | ret = -EINVAL; | |
1252 | if (vma->vm_start >= end) | |
1253 | goto out_unlock; | |
1254 | ||
cab350af MK |
1255 | /* |
1256 | * If the first vma contains huge pages, make sure start address | |
1257 | * is aligned to huge page size. | |
1258 | */ | |
1259 | if (is_vm_hugetlb_page(vma)) { | |
1260 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1261 | ||
1262 | if (start & (vma_hpagesize - 1)) | |
1263 | goto out_unlock; | |
1264 | } | |
1265 | ||
86039bd3 AA |
1266 | /* |
1267 | * Search for not compatible vmas. | |
86039bd3 AA |
1268 | */ |
1269 | found = false; | |
ce53e8e6 | 1270 | basic_ioctls = false; |
86039bd3 AA |
1271 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { |
1272 | cond_resched(); | |
1273 | ||
1274 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1275 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1276 | ||
1277 | /* check not compatible vmas */ | |
1278 | ret = -EINVAL; | |
ba6907db | 1279 | if (!vma_can_userfault(cur)) |
86039bd3 | 1280 | goto out_unlock; |
cab350af MK |
1281 | /* |
1282 | * If this vma contains ending address, and huge pages | |
1283 | * check alignment. | |
1284 | */ | |
1285 | if (is_vm_hugetlb_page(cur) && end <= cur->vm_end && | |
1286 | end > cur->vm_start) { | |
1287 | unsigned long vma_hpagesize = vma_kernel_pagesize(cur); | |
1288 | ||
1289 | ret = -EINVAL; | |
1290 | ||
1291 | if (end & (vma_hpagesize - 1)) | |
1292 | goto out_unlock; | |
1293 | } | |
86039bd3 AA |
1294 | |
1295 | /* | |
1296 | * Check that this vma isn't already owned by a | |
1297 | * different userfaultfd. We can't allow more than one | |
1298 | * userfaultfd to own a single vma simultaneously or we | |
1299 | * wouldn't know which one to deliver the userfaults to. | |
1300 | */ | |
1301 | ret = -EBUSY; | |
1302 | if (cur->vm_userfaultfd_ctx.ctx && | |
1303 | cur->vm_userfaultfd_ctx.ctx != ctx) | |
1304 | goto out_unlock; | |
1305 | ||
cab350af MK |
1306 | /* |
1307 | * Note vmas containing huge pages | |
1308 | */ | |
ce53e8e6 MR |
1309 | if (is_vm_hugetlb_page(cur)) |
1310 | basic_ioctls = true; | |
cab350af | 1311 | |
86039bd3 AA |
1312 | found = true; |
1313 | } | |
1314 | BUG_ON(!found); | |
1315 | ||
1316 | if (vma->vm_start < start) | |
1317 | prev = vma; | |
1318 | ||
1319 | ret = 0; | |
1320 | do { | |
1321 | cond_resched(); | |
1322 | ||
ba6907db | 1323 | BUG_ON(!vma_can_userfault(vma)); |
86039bd3 AA |
1324 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
1325 | vma->vm_userfaultfd_ctx.ctx != ctx); | |
1326 | ||
1327 | /* | |
1328 | * Nothing to do: this vma is already registered into this | |
1329 | * userfaultfd and with the right tracking mode too. | |
1330 | */ | |
1331 | if (vma->vm_userfaultfd_ctx.ctx == ctx && | |
1332 | (vma->vm_flags & vm_flags) == vm_flags) | |
1333 | goto skip; | |
1334 | ||
1335 | if (vma->vm_start > start) | |
1336 | start = vma->vm_start; | |
1337 | vma_end = min(end, vma->vm_end); | |
1338 | ||
1339 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; | |
1340 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1341 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1342 | vma_policy(vma), | |
1343 | ((struct vm_userfaultfd_ctx){ ctx })); | |
1344 | if (prev) { | |
1345 | vma = prev; | |
1346 | goto next; | |
1347 | } | |
1348 | if (vma->vm_start < start) { | |
1349 | ret = split_vma(mm, vma, start, 1); | |
1350 | if (ret) | |
1351 | break; | |
1352 | } | |
1353 | if (vma->vm_end > end) { | |
1354 | ret = split_vma(mm, vma, end, 0); | |
1355 | if (ret) | |
1356 | break; | |
1357 | } | |
1358 | next: | |
1359 | /* | |
1360 | * In the vma_merge() successful mprotect-like case 8: | |
1361 | * the next vma was merged into the current one and | |
1362 | * the current one has not been updated yet. | |
1363 | */ | |
1364 | vma->vm_flags = new_flags; | |
1365 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
1366 | ||
1367 | skip: | |
1368 | prev = vma; | |
1369 | start = vma->vm_end; | |
1370 | vma = vma->vm_next; | |
1371 | } while (vma && vma->vm_start < end); | |
1372 | out_unlock: | |
1373 | up_write(&mm->mmap_sem); | |
d2005e3f | 1374 | mmput(mm); |
86039bd3 AA |
1375 | if (!ret) { |
1376 | /* | |
1377 | * Now that we scanned all vmas we can already tell | |
1378 | * userland which ioctls methods are guaranteed to | |
1379 | * succeed on this range. | |
1380 | */ | |
ce53e8e6 | 1381 | if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC : |
cab350af | 1382 | UFFD_API_RANGE_IOCTLS, |
86039bd3 AA |
1383 | &user_uffdio_register->ioctls)) |
1384 | ret = -EFAULT; | |
1385 | } | |
1386 | out: | |
1387 | return ret; | |
1388 | } | |
1389 | ||
1390 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, | |
1391 | unsigned long arg) | |
1392 | { | |
1393 | struct mm_struct *mm = ctx->mm; | |
1394 | struct vm_area_struct *vma, *prev, *cur; | |
1395 | int ret; | |
1396 | struct uffdio_range uffdio_unregister; | |
1397 | unsigned long new_flags; | |
1398 | bool found; | |
1399 | unsigned long start, end, vma_end; | |
1400 | const void __user *buf = (void __user *)arg; | |
1401 | ||
1402 | ret = -EFAULT; | |
1403 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) | |
1404 | goto out; | |
1405 | ||
1406 | ret = validate_range(mm, uffdio_unregister.start, | |
1407 | uffdio_unregister.len); | |
1408 | if (ret) | |
1409 | goto out; | |
1410 | ||
1411 | start = uffdio_unregister.start; | |
1412 | end = start + uffdio_unregister.len; | |
1413 | ||
d2005e3f ON |
1414 | ret = -ENOMEM; |
1415 | if (!mmget_not_zero(mm)) | |
1416 | goto out; | |
1417 | ||
86039bd3 AA |
1418 | down_write(&mm->mmap_sem); |
1419 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1420 | if (!vma) |
1421 | goto out_unlock; | |
1422 | ||
1423 | /* check that there's at least one vma in the range */ | |
1424 | ret = -EINVAL; | |
1425 | if (vma->vm_start >= end) | |
1426 | goto out_unlock; | |
1427 | ||
cab350af MK |
1428 | /* |
1429 | * If the first vma contains huge pages, make sure start address | |
1430 | * is aligned to huge page size. | |
1431 | */ | |
1432 | if (is_vm_hugetlb_page(vma)) { | |
1433 | unsigned long vma_hpagesize = vma_kernel_pagesize(vma); | |
1434 | ||
1435 | if (start & (vma_hpagesize - 1)) | |
1436 | goto out_unlock; | |
1437 | } | |
1438 | ||
86039bd3 AA |
1439 | /* |
1440 | * Search for not compatible vmas. | |
86039bd3 AA |
1441 | */ |
1442 | found = false; | |
1443 | ret = -EINVAL; | |
1444 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { | |
1445 | cond_resched(); | |
1446 | ||
1447 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1448 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1449 | ||
1450 | /* | |
1451 | * Check not compatible vmas, not strictly required | |
1452 | * here as not compatible vmas cannot have an | |
1453 | * userfaultfd_ctx registered on them, but this | |
1454 | * provides for more strict behavior to notice | |
1455 | * unregistration errors. | |
1456 | */ | |
ba6907db | 1457 | if (!vma_can_userfault(cur)) |
86039bd3 AA |
1458 | goto out_unlock; |
1459 | ||
1460 | found = true; | |
1461 | } | |
1462 | BUG_ON(!found); | |
1463 | ||
1464 | if (vma->vm_start < start) | |
1465 | prev = vma; | |
1466 | ||
1467 | ret = 0; | |
1468 | do { | |
1469 | cond_resched(); | |
1470 | ||
ba6907db | 1471 | BUG_ON(!vma_can_userfault(vma)); |
86039bd3 AA |
1472 | |
1473 | /* | |
1474 | * Nothing to do: this vma is already registered into this | |
1475 | * userfaultfd and with the right tracking mode too. | |
1476 | */ | |
1477 | if (!vma->vm_userfaultfd_ctx.ctx) | |
1478 | goto skip; | |
1479 | ||
1480 | if (vma->vm_start > start) | |
1481 | start = vma->vm_start; | |
1482 | vma_end = min(end, vma->vm_end); | |
1483 | ||
09fa5296 AA |
1484 | if (userfaultfd_missing(vma)) { |
1485 | /* | |
1486 | * Wake any concurrent pending userfault while | |
1487 | * we unregister, so they will not hang | |
1488 | * permanently and it avoids userland to call | |
1489 | * UFFDIO_WAKE explicitly. | |
1490 | */ | |
1491 | struct userfaultfd_wake_range range; | |
1492 | range.start = start; | |
1493 | range.len = vma_end - start; | |
1494 | wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range); | |
1495 | } | |
1496 | ||
86039bd3 AA |
1497 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); |
1498 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1499 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1500 | vma_policy(vma), | |
1501 | NULL_VM_UFFD_CTX); | |
1502 | if (prev) { | |
1503 | vma = prev; | |
1504 | goto next; | |
1505 | } | |
1506 | if (vma->vm_start < start) { | |
1507 | ret = split_vma(mm, vma, start, 1); | |
1508 | if (ret) | |
1509 | break; | |
1510 | } | |
1511 | if (vma->vm_end > end) { | |
1512 | ret = split_vma(mm, vma, end, 0); | |
1513 | if (ret) | |
1514 | break; | |
1515 | } | |
1516 | next: | |
1517 | /* | |
1518 | * In the vma_merge() successful mprotect-like case 8: | |
1519 | * the next vma was merged into the current one and | |
1520 | * the current one has not been updated yet. | |
1521 | */ | |
1522 | vma->vm_flags = new_flags; | |
1523 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
1524 | ||
1525 | skip: | |
1526 | prev = vma; | |
1527 | start = vma->vm_end; | |
1528 | vma = vma->vm_next; | |
1529 | } while (vma && vma->vm_start < end); | |
1530 | out_unlock: | |
1531 | up_write(&mm->mmap_sem); | |
d2005e3f | 1532 | mmput(mm); |
86039bd3 AA |
1533 | out: |
1534 | return ret; | |
1535 | } | |
1536 | ||
1537 | /* | |
ba85c702 AA |
1538 | * userfaultfd_wake may be used in combination with the |
1539 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. | |
86039bd3 AA |
1540 | */ |
1541 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, | |
1542 | unsigned long arg) | |
1543 | { | |
1544 | int ret; | |
1545 | struct uffdio_range uffdio_wake; | |
1546 | struct userfaultfd_wake_range range; | |
1547 | const void __user *buf = (void __user *)arg; | |
1548 | ||
1549 | ret = -EFAULT; | |
1550 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) | |
1551 | goto out; | |
1552 | ||
1553 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); | |
1554 | if (ret) | |
1555 | goto out; | |
1556 | ||
1557 | range.start = uffdio_wake.start; | |
1558 | range.len = uffdio_wake.len; | |
1559 | ||
1560 | /* | |
1561 | * len == 0 means wake all and we don't want to wake all here, | |
1562 | * so check it again to be sure. | |
1563 | */ | |
1564 | VM_BUG_ON(!range.len); | |
1565 | ||
1566 | wake_userfault(ctx, &range); | |
1567 | ret = 0; | |
1568 | ||
1569 | out: | |
1570 | return ret; | |
1571 | } | |
1572 | ||
ad465cae AA |
1573 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
1574 | unsigned long arg) | |
1575 | { | |
1576 | __s64 ret; | |
1577 | struct uffdio_copy uffdio_copy; | |
1578 | struct uffdio_copy __user *user_uffdio_copy; | |
1579 | struct userfaultfd_wake_range range; | |
1580 | ||
1581 | user_uffdio_copy = (struct uffdio_copy __user *) arg; | |
1582 | ||
1583 | ret = -EFAULT; | |
1584 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, | |
1585 | /* don't copy "copy" last field */ | |
1586 | sizeof(uffdio_copy)-sizeof(__s64))) | |
1587 | goto out; | |
1588 | ||
1589 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); | |
1590 | if (ret) | |
1591 | goto out; | |
1592 | /* | |
1593 | * double check for wraparound just in case. copy_from_user() | |
1594 | * will later check uffdio_copy.src + uffdio_copy.len to fit | |
1595 | * in the userland range. | |
1596 | */ | |
1597 | ret = -EINVAL; | |
1598 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) | |
1599 | goto out; | |
1600 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) | |
1601 | goto out; | |
d2005e3f ON |
1602 | if (mmget_not_zero(ctx->mm)) { |
1603 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, | |
1604 | uffdio_copy.len); | |
1605 | mmput(ctx->mm); | |
96333187 | 1606 | } else { |
e86b298b | 1607 | return -ESRCH; |
d2005e3f | 1608 | } |
ad465cae AA |
1609 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
1610 | return -EFAULT; | |
1611 | if (ret < 0) | |
1612 | goto out; | |
1613 | BUG_ON(!ret); | |
1614 | /* len == 0 would wake all */ | |
1615 | range.len = ret; | |
1616 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { | |
1617 | range.start = uffdio_copy.dst; | |
1618 | wake_userfault(ctx, &range); | |
1619 | } | |
1620 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; | |
1621 | out: | |
1622 | return ret; | |
1623 | } | |
1624 | ||
1625 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, | |
1626 | unsigned long arg) | |
1627 | { | |
1628 | __s64 ret; | |
1629 | struct uffdio_zeropage uffdio_zeropage; | |
1630 | struct uffdio_zeropage __user *user_uffdio_zeropage; | |
1631 | struct userfaultfd_wake_range range; | |
1632 | ||
1633 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; | |
1634 | ||
1635 | ret = -EFAULT; | |
1636 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, | |
1637 | /* don't copy "zeropage" last field */ | |
1638 | sizeof(uffdio_zeropage)-sizeof(__s64))) | |
1639 | goto out; | |
1640 | ||
1641 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, | |
1642 | uffdio_zeropage.range.len); | |
1643 | if (ret) | |
1644 | goto out; | |
1645 | ret = -EINVAL; | |
1646 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) | |
1647 | goto out; | |
1648 | ||
d2005e3f ON |
1649 | if (mmget_not_zero(ctx->mm)) { |
1650 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, | |
1651 | uffdio_zeropage.range.len); | |
1652 | mmput(ctx->mm); | |
9d95aa4b | 1653 | } else { |
e86b298b | 1654 | return -ESRCH; |
d2005e3f | 1655 | } |
ad465cae AA |
1656 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
1657 | return -EFAULT; | |
1658 | if (ret < 0) | |
1659 | goto out; | |
1660 | /* len == 0 would wake all */ | |
1661 | BUG_ON(!ret); | |
1662 | range.len = ret; | |
1663 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { | |
1664 | range.start = uffdio_zeropage.range.start; | |
1665 | wake_userfault(ctx, &range); | |
1666 | } | |
1667 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; | |
1668 | out: | |
1669 | return ret; | |
1670 | } | |
1671 | ||
9cd75c3c PE |
1672 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
1673 | { | |
1674 | /* | |
1675 | * For the current set of features the bits just coincide | |
1676 | */ | |
1677 | return (unsigned int)user_features; | |
1678 | } | |
1679 | ||
86039bd3 AA |
1680 | /* |
1681 | * userland asks for a certain API version and we return which bits | |
1682 | * and ioctl commands are implemented in this kernel for such API | |
1683 | * version or -EINVAL if unknown. | |
1684 | */ | |
1685 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, | |
1686 | unsigned long arg) | |
1687 | { | |
1688 | struct uffdio_api uffdio_api; | |
1689 | void __user *buf = (void __user *)arg; | |
1690 | int ret; | |
65603144 | 1691 | __u64 features; |
86039bd3 AA |
1692 | |
1693 | ret = -EINVAL; | |
1694 | if (ctx->state != UFFD_STATE_WAIT_API) | |
1695 | goto out; | |
1696 | ret = -EFAULT; | |
a9b85f94 | 1697 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
86039bd3 | 1698 | goto out; |
65603144 AA |
1699 | features = uffdio_api.features; |
1700 | if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { | |
86039bd3 AA |
1701 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
1702 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1703 | goto out; | |
1704 | ret = -EINVAL; | |
1705 | goto out; | |
1706 | } | |
65603144 AA |
1707 | /* report all available features and ioctls to userland */ |
1708 | uffdio_api.features = UFFD_API_FEATURES; | |
86039bd3 AA |
1709 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
1710 | ret = -EFAULT; | |
1711 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1712 | goto out; | |
1713 | ctx->state = UFFD_STATE_RUNNING; | |
65603144 AA |
1714 | /* only enable the requested features for this uffd context */ |
1715 | ctx->features = uffd_ctx_features(features); | |
86039bd3 AA |
1716 | ret = 0; |
1717 | out: | |
1718 | return ret; | |
1719 | } | |
1720 | ||
1721 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, | |
1722 | unsigned long arg) | |
1723 | { | |
1724 | int ret = -EINVAL; | |
1725 | struct userfaultfd_ctx *ctx = file->private_data; | |
1726 | ||
e6485a47 AA |
1727 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
1728 | return -EINVAL; | |
1729 | ||
86039bd3 AA |
1730 | switch(cmd) { |
1731 | case UFFDIO_API: | |
1732 | ret = userfaultfd_api(ctx, arg); | |
1733 | break; | |
1734 | case UFFDIO_REGISTER: | |
1735 | ret = userfaultfd_register(ctx, arg); | |
1736 | break; | |
1737 | case UFFDIO_UNREGISTER: | |
1738 | ret = userfaultfd_unregister(ctx, arg); | |
1739 | break; | |
1740 | case UFFDIO_WAKE: | |
1741 | ret = userfaultfd_wake(ctx, arg); | |
1742 | break; | |
ad465cae AA |
1743 | case UFFDIO_COPY: |
1744 | ret = userfaultfd_copy(ctx, arg); | |
1745 | break; | |
1746 | case UFFDIO_ZEROPAGE: | |
1747 | ret = userfaultfd_zeropage(ctx, arg); | |
1748 | break; | |
86039bd3 AA |
1749 | } |
1750 | return ret; | |
1751 | } | |
1752 | ||
1753 | #ifdef CONFIG_PROC_FS | |
1754 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) | |
1755 | { | |
1756 | struct userfaultfd_ctx *ctx = f->private_data; | |
ac6424b9 | 1757 | wait_queue_entry_t *wq; |
86039bd3 AA |
1758 | struct userfaultfd_wait_queue *uwq; |
1759 | unsigned long pending = 0, total = 0; | |
1760 | ||
15b726ef | 1761 | spin_lock(&ctx->fault_pending_wqh.lock); |
2055da97 | 1762 | list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { |
15b726ef AA |
1763 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
1764 | pending++; | |
1765 | total++; | |
1766 | } | |
2055da97 | 1767 | list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { |
86039bd3 | 1768 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
86039bd3 AA |
1769 | total++; |
1770 | } | |
15b726ef | 1771 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1772 | |
1773 | /* | |
1774 | * If more protocols will be added, there will be all shown | |
1775 | * separated by a space. Like this: | |
1776 | * protocols: aa:... bb:... | |
1777 | */ | |
1778 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", | |
045098e9 | 1779 | pending, total, UFFD_API, ctx->features, |
86039bd3 AA |
1780 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
1781 | } | |
1782 | #endif | |
1783 | ||
1784 | static const struct file_operations userfaultfd_fops = { | |
1785 | #ifdef CONFIG_PROC_FS | |
1786 | .show_fdinfo = userfaultfd_show_fdinfo, | |
1787 | #endif | |
1788 | .release = userfaultfd_release, | |
1789 | .poll = userfaultfd_poll, | |
1790 | .read = userfaultfd_read, | |
1791 | .unlocked_ioctl = userfaultfd_ioctl, | |
1792 | .compat_ioctl = userfaultfd_ioctl, | |
1793 | .llseek = noop_llseek, | |
1794 | }; | |
1795 | ||
3004ec9c AA |
1796 | static void init_once_userfaultfd_ctx(void *mem) |
1797 | { | |
1798 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; | |
1799 | ||
1800 | init_waitqueue_head(&ctx->fault_pending_wqh); | |
1801 | init_waitqueue_head(&ctx->fault_wqh); | |
9cd75c3c | 1802 | init_waitqueue_head(&ctx->event_wqh); |
3004ec9c | 1803 | init_waitqueue_head(&ctx->fd_wqh); |
2c5b7e1b | 1804 | seqcount_init(&ctx->refile_seq); |
3004ec9c AA |
1805 | } |
1806 | ||
86039bd3 | 1807 | /** |
9332ef9d | 1808 | * userfaultfd_file_create - Creates a userfaultfd file pointer. |
86039bd3 AA |
1809 | * @flags: Flags for the userfaultfd file. |
1810 | * | |
9332ef9d | 1811 | * This function creates a userfaultfd file pointer, w/out installing |
86039bd3 AA |
1812 | * it into the fd table. This is useful when the userfaultfd file is |
1813 | * used during the initialization of data structures that require | |
1814 | * extra setup after the userfaultfd creation. So the userfaultfd | |
1815 | * creation is split into the file pointer creation phase, and the | |
1816 | * file descriptor installation phase. In this way races with | |
1817 | * userspace closing the newly installed file descriptor can be | |
9332ef9d | 1818 | * avoided. Returns a userfaultfd file pointer, or a proper error |
86039bd3 AA |
1819 | * pointer. |
1820 | */ | |
1821 | static struct file *userfaultfd_file_create(int flags) | |
1822 | { | |
1823 | struct file *file; | |
1824 | struct userfaultfd_ctx *ctx; | |
1825 | ||
1826 | BUG_ON(!current->mm); | |
1827 | ||
1828 | /* Check the UFFD_* constants for consistency. */ | |
1829 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); | |
1830 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); | |
1831 | ||
1832 | file = ERR_PTR(-EINVAL); | |
1833 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) | |
1834 | goto out; | |
1835 | ||
1836 | file = ERR_PTR(-ENOMEM); | |
3004ec9c | 1837 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
86039bd3 AA |
1838 | if (!ctx) |
1839 | goto out; | |
1840 | ||
1841 | atomic_set(&ctx->refcount, 1); | |
86039bd3 | 1842 | ctx->flags = flags; |
9cd75c3c | 1843 | ctx->features = 0; |
86039bd3 AA |
1844 | ctx->state = UFFD_STATE_WAIT_API; |
1845 | ctx->released = false; | |
1846 | ctx->mm = current->mm; | |
1847 | /* prevent the mm struct to be freed */ | |
f1f10076 | 1848 | mmgrab(ctx->mm); |
86039bd3 AA |
1849 | |
1850 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx, | |
1851 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); | |
c03e946f | 1852 | if (IS_ERR(file)) { |
d2005e3f | 1853 | mmdrop(ctx->mm); |
3004ec9c | 1854 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
c03e946f | 1855 | } |
86039bd3 AA |
1856 | out: |
1857 | return file; | |
1858 | } | |
1859 | ||
1860 | SYSCALL_DEFINE1(userfaultfd, int, flags) | |
1861 | { | |
1862 | int fd, error; | |
1863 | struct file *file; | |
1864 | ||
1865 | error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); | |
1866 | if (error < 0) | |
1867 | return error; | |
1868 | fd = error; | |
1869 | ||
1870 | file = userfaultfd_file_create(flags); | |
1871 | if (IS_ERR(file)) { | |
1872 | error = PTR_ERR(file); | |
1873 | goto err_put_unused_fd; | |
1874 | } | |
1875 | fd_install(fd, file); | |
1876 | ||
1877 | return fd; | |
1878 | ||
1879 | err_put_unused_fd: | |
1880 | put_unused_fd(fd); | |
1881 | ||
1882 | return error; | |
1883 | } | |
3004ec9c AA |
1884 | |
1885 | static int __init userfaultfd_init(void) | |
1886 | { | |
1887 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", | |
1888 | sizeof(struct userfaultfd_ctx), | |
1889 | 0, | |
1890 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, | |
1891 | init_once_userfaultfd_ctx); | |
1892 | return 0; | |
1893 | } | |
1894 | __initcall(userfaultfd_init); |