blob: f7555fc25877435e13b65cbe597ae9bdb11c6528 [file] [log] [blame]
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001/*
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
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -080015#include <linux/list.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070016#include <linux/hashtable.h>
Ingo Molnar174cd4b2017-02-02 19:15:33 +010017#include <linux/sched/signal.h>
Ingo Molnar6e84f312017-02-08 18:51:29 +010018#include <linux/sched/mm.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070019#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>
Mike Kravetzcab350a2017-02-22 15:43:04 -080031#include <linux/hugetlb.h>
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070032
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070033static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
34
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070035enum userfaultfd_state {
36 UFFD_STATE_WAIT_API,
37 UFFD_STATE_RUNNING,
38};
39
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070040/*
41 * Start with fault_pending_wqh and fault_wqh so they're more likely
42 * to be in the same cacheline.
43 */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070044struct userfaultfd_ctx {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -070045 /* waitqueue head for the pending (i.e. not read) userfaults */
46 wait_queue_head_t fault_pending_wqh;
47 /* waitqueue head for the userfaults */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070048 wait_queue_head_t fault_wqh;
49 /* waitqueue head for the pseudo fd to wakeup poll/read */
50 wait_queue_head_t fd_wqh;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -080051 /* waitqueue head for events */
52 wait_queue_head_t event_wqh;
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -070053 /* a refile sequence protected by fault_pending_wqh lock */
54 struct seqcount refile_seq;
Andrea Arcangeli3004ec92015-09-04 15:46:48 -070055 /* pseudo fd refcounting */
56 atomic_t refcount;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070057 /* userfaultfd syscall flags */
58 unsigned int flags;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -080059 /* features requested from the userspace */
60 unsigned int features;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070061 /* 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
Pavel Emelyanov893e26e2017-02-22 15:42:27 -080069struct userfaultfd_fork_ctx {
70 struct userfaultfd_ctx *orig;
71 struct userfaultfd_ctx *new;
72 struct list_head list;
73};
74
Mike Rapoport897ab3e2017-02-24 14:58:22 -080075struct userfaultfd_unmap_ctx {
76 struct userfaultfd_ctx *ctx;
77 unsigned long start;
78 unsigned long end;
79 struct list_head list;
80};
81
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070082struct userfaultfd_wait_queue {
Andrea Arcangelia9b85f92015-09-04 15:46:37 -070083 struct uffd_msg msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070084 wait_queue_t wq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070085 struct userfaultfd_ctx *ctx;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -080086 bool waken;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -070087};
88
89struct userfaultfd_wake_range {
90 unsigned long start;
91 unsigned long len;
92};
93
94static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode,
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;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700104 /* len == 0 means wake all */
105 start = range->start;
106 len = range->len;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700107 if (len && (start > uwq->msg.arg.pagefault.address ||
108 start + len <= uwq->msg.arg.pagefault.address))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700109 goto out;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800110 WRITE_ONCE(uwq->waken, true);
111 /*
112 * The implicit smp_mb__before_spinlock in try_to_wake_up()
113 * renders uwq->waken visible to other CPUs before the task is
114 * waken.
115 */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700116 ret = wake_up_state(wq->private, mode);
117 if (ret)
118 /*
119 * Wake only once, autoremove behavior.
120 *
121 * After the effect of list_del_init is visible to the
122 * other CPUs, the waitqueue may disappear from under
123 * us, see the !list_empty_careful() in
124 * handle_userfault(). try_to_wake_up() has an
125 * implicit smp_mb__before_spinlock, and the
126 * wq->private is read before calling the extern
127 * function "wake_up_state" (which in turns calls
128 * try_to_wake_up). While the spin_lock;spin_unlock;
129 * wouldn't be enough, the smp_mb__before_spinlock is
130 * enough to avoid an explicit smp_mb() here.
131 */
132 list_del_init(&wq->task_list);
133out:
134 return ret;
135}
136
137/**
138 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd
139 * context.
140 * @ctx: [in] Pointer to the userfaultfd context.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700141 */
142static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
143{
144 if (!atomic_inc_not_zero(&ctx->refcount))
145 BUG();
146}
147
148/**
149 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
150 * context.
151 * @ctx: [in] Pointer to userfaultfd context.
152 *
153 * The userfaultfd context reference must have been previously acquired either
154 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
155 */
156static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
157{
158 if (atomic_dec_and_test(&ctx->refcount)) {
159 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
160 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
161 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
162 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800163 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock));
164 VM_BUG_ON(waitqueue_active(&ctx->event_wqh));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700165 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
166 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700167 mmdrop(ctx->mm);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -0700168 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700169 }
170}
171
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700172static inline void msg_init(struct uffd_msg *msg)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700173{
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700174 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
175 /*
176 * Must use memset to zero out the paddings or kernel data is
177 * leaked to userland.
178 */
179 memset(msg, 0, sizeof(struct uffd_msg));
180}
181
182static inline struct uffd_msg userfault_msg(unsigned long address,
183 unsigned int flags,
184 unsigned long reason)
185{
186 struct uffd_msg msg;
187 msg_init(&msg);
188 msg.event = UFFD_EVENT_PAGEFAULT;
189 msg.arg.pagefault.address = address;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700190 if (flags & FAULT_FLAG_WRITE)
191 /*
Andrea Arcangelia4605a62017-02-22 15:42:09 -0800192 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700193 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE
194 * was not set in a UFFD_EVENT_PAGEFAULT, it means it
195 * was a read fault, otherwise if set it means it's
196 * a write fault.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700197 */
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700198 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700199 if (reason & VM_UFFD_WP)
200 /*
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700201 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
202 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was
203 * not set in a UFFD_EVENT_PAGEFAULT, it means it was
204 * a missing fault, otherwise if set it means it's a
205 * write protect fault.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700206 */
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700207 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
208 return msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700209}
210
Mike Kravetz369cd212017-02-22 15:43:10 -0800211#ifdef CONFIG_HUGETLB_PAGE
212/*
213 * Same functionality as userfaultfd_must_wait below with modifications for
214 * hugepmd ranges.
215 */
216static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
217 unsigned long address,
218 unsigned long flags,
219 unsigned long reason)
220{
221 struct mm_struct *mm = ctx->mm;
222 pte_t *pte;
223 bool ret = true;
224
225 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
226
227 pte = huge_pte_offset(mm, address);
228 if (!pte)
229 goto out;
230
231 ret = false;
232
233 /*
234 * Lockless access: we're in a wait_event so it's ok if it
235 * changes under us.
236 */
237 if (huge_pte_none(*pte))
238 ret = true;
239 if (!huge_pte_write(*pte) && (reason & VM_UFFD_WP))
240 ret = true;
241out:
242 return ret;
243}
244#else
245static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
246 unsigned long address,
247 unsigned long flags,
248 unsigned long reason)
249{
250 return false; /* should never get here */
251}
252#endif /* CONFIG_HUGETLB_PAGE */
253
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700254/*
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700255 * Verify the pagetables are still not ok after having reigstered into
256 * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
257 * userfault that has already been resolved, if userfaultfd_read and
258 * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
259 * threads.
260 */
261static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
262 unsigned long address,
263 unsigned long flags,
264 unsigned long reason)
265{
266 struct mm_struct *mm = ctx->mm;
267 pgd_t *pgd;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300268 p4d_t *p4d;
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700269 pud_t *pud;
270 pmd_t *pmd, _pmd;
271 pte_t *pte;
272 bool ret = true;
273
274 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
275
276 pgd = pgd_offset(mm, address);
277 if (!pgd_present(*pgd))
278 goto out;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300279 p4d = p4d_offset(pgd, address);
280 if (!p4d_present(*p4d))
281 goto out;
282 pud = pud_offset(p4d, address);
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700283 if (!pud_present(*pud))
284 goto out;
285 pmd = pmd_offset(pud, address);
286 /*
287 * READ_ONCE must function as a barrier with narrower scope
288 * and it must be equivalent to:
289 * _pmd = *pmd; barrier();
290 *
291 * This is to deal with the instability (as in
292 * pmd_trans_unstable) of the pmd.
293 */
294 _pmd = READ_ONCE(*pmd);
295 if (!pmd_present(_pmd))
296 goto out;
297
298 ret = false;
299 if (pmd_trans_huge(_pmd))
300 goto out;
301
302 /*
303 * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it
304 * and use the standard pte_offset_map() instead of parsing _pmd.
305 */
306 pte = pte_offset_map(pmd, address);
307 /*
308 * Lockless access: we're in a wait_event so it's ok if it
309 * changes under us.
310 */
311 if (pte_none(*pte))
312 ret = true;
313 pte_unmap(pte);
314
315out:
316 return ret;
317}
318
319/*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700320 * The locking rules involved in returning VM_FAULT_RETRY depending on
321 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
322 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
323 * recommendation in __lock_page_or_retry is not an understatement.
324 *
325 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released
326 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
327 * not set.
328 *
329 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
330 * set, VM_FAULT_RETRY can still be returned if and only if there are
331 * fatal_signal_pending()s, and the mmap_sem must be released before
332 * returning it.
333 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800334int handle_userfault(struct vm_fault *vmf, unsigned long reason)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700335{
Jan Kara82b0f8c2016-12-14 15:06:58 -0800336 struct mm_struct *mm = vmf->vma->vm_mm;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700337 struct userfaultfd_ctx *ctx;
338 struct userfaultfd_wait_queue uwq;
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700339 int ret;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700340 bool must_wait, return_to_userland;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800341 long blocking_state;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700342
343 BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
344
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700345 ret = VM_FAULT_SIGBUS;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800346 ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700347 if (!ctx)
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700348 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700349
350 BUG_ON(ctx->mm != mm);
351
352 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
353 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
354
355 /*
356 * If it's already released don't get it. This avoids to loop
357 * in __get_user_pages if userfaultfd_release waits on the
358 * caller of handle_userfault to release the mmap_sem.
359 */
360 if (unlikely(ACCESS_ONCE(ctx->released)))
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700361 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700362
363 /*
Linus Torvalds39680f52016-03-01 11:56:22 -0800364 * We don't do userfault handling for the final child pid update.
365 */
366 if (current->flags & PF_EXITING)
367 goto out;
368
369 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700370 * Check that we can return VM_FAULT_RETRY.
371 *
372 * NOTE: it should become possible to return VM_FAULT_RETRY
373 * even if FAULT_FLAG_TRIED is set without leading to gup()
374 * -EBUSY failures, if the userfaultfd is to be extended for
375 * VM_UFFD_WP tracking and we intend to arm the userfault
376 * without first stopping userland access to the memory. For
377 * VM_UFFD_MISSING userfaults this is enough for now.
378 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800379 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700380 /*
381 * Validate the invariant that nowait must allow retry
382 * to be sure not to return SIGBUS erroneously on
383 * nowait invocations.
384 */
Jan Kara82b0f8c2016-12-14 15:06:58 -0800385 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700386#ifdef CONFIG_DEBUG_VM
387 if (printk_ratelimit()) {
388 printk(KERN_WARNING
Jan Kara82b0f8c2016-12-14 15:06:58 -0800389 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
390 vmf->flags);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700391 dump_stack();
392 }
393#endif
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700394 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700395 }
396
397 /*
398 * Handle nowait, not much to do other than tell it to retry
399 * and wait.
400 */
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700401 ret = VM_FAULT_RETRY;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800402 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700403 goto out;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700404
405 /* take the reference before dropping the mmap_sem */
406 userfaultfd_ctx_get(ctx);
407
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700408 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
409 uwq.wq.private = current;
Jan Kara82b0f8c2016-12-14 15:06:58 -0800410 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700411 uwq.ctx = ctx;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800412 uwq.waken = false;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700413
Kirill A. Shutemovbae473a2016-07-26 15:25:20 -0700414 return_to_userland =
Jan Kara82b0f8c2016-12-14 15:06:58 -0800415 (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700416 (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800417 blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
418 TASK_KILLABLE;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700419
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700420 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700421 /*
422 * After the __add_wait_queue the uwq is visible to userland
423 * through poll/read().
424 */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700425 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq);
426 /*
427 * The smp_mb() after __set_current_state prevents the reads
428 * following the spin_unlock to happen before the list_add in
429 * __add_wait_queue.
430 */
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800431 set_current_state(blocking_state);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700432 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700433
Mike Kravetz369cd212017-02-22 15:43:10 -0800434 if (!is_vm_hugetlb_page(vmf->vma))
435 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
436 reason);
437 else
438 must_wait = userfaultfd_huge_must_wait(ctx, vmf->address,
439 vmf->flags, reason);
Andrea Arcangeli8d2afd92015-09-04 15:46:51 -0700440 up_read(&mm->mmap_sem);
441
442 if (likely(must_wait && !ACCESS_ONCE(ctx->released) &&
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700443 (return_to_userland ? !signal_pending(current) :
444 !fatal_signal_pending(current)))) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700445 wake_up_poll(&ctx->fd_wqh, POLLIN);
446 schedule();
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700447 ret |= VM_FAULT_MAJOR;
Andrea Arcangeli15a77c62017-01-24 15:17:59 -0800448
449 /*
450 * False wakeups can orginate even from rwsem before
451 * up_read() however userfaults will wait either for a
452 * targeted wakeup on the specific uwq waitqueue from
453 * wake_userfault() or for signals or for uffd
454 * release.
455 */
456 while (!READ_ONCE(uwq.waken)) {
457 /*
458 * This needs the full smp_store_mb()
459 * guarantee as the state write must be
460 * visible to other CPUs before reading
461 * uwq.waken from other CPUs.
462 */
463 set_current_state(blocking_state);
464 if (READ_ONCE(uwq.waken) ||
465 READ_ONCE(ctx->released) ||
466 (return_to_userland ? signal_pending(current) :
467 fatal_signal_pending(current)))
468 break;
469 schedule();
470 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700471 }
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700472
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700473 __set_current_state(TASK_RUNNING);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700474
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700475 if (return_to_userland) {
476 if (signal_pending(current) &&
477 !fatal_signal_pending(current)) {
478 /*
479 * If we got a SIGSTOP or SIGCONT and this is
480 * a normal userland page fault, just let
481 * userland return so the signal will be
482 * handled and gdb debugging works. The page
483 * fault code immediately after we return from
484 * this function is going to release the
485 * mmap_sem and it's not depending on it
486 * (unlike gup would if we were not to return
487 * VM_FAULT_RETRY).
488 *
489 * If a fatal signal is pending we still take
490 * the streamlined VM_FAULT_RETRY failure path
491 * and there's no need to retake the mmap_sem
492 * in such case.
493 */
494 down_read(&mm->mmap_sem);
Andrea Arcangeli6bbc4a42017-03-09 16:16:28 -0800495 ret = VM_FAULT_NOPAGE;
Andrea Arcangelidfa37dc2015-09-04 15:47:18 -0700496 }
497 }
498
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700499 /*
500 * Here we race with the list_del; list_add in
501 * userfaultfd_ctx_read(), however because we don't ever run
502 * list_del_init() to refile across the two lists, the prev
503 * and next pointers will never point to self. list_add also
504 * would never let any of the two pointers to point to
505 * self. So list_empty_careful won't risk to see both pointers
506 * pointing to self at any time during the list refile. The
507 * only case where list_del_init() is called is the full
508 * removal in the wake function and there we don't re-list_add
509 * and it's fine not to block on the spinlock. The uwq on this
510 * kernel stack can be released after the list_del_init.
511 */
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700512 if (!list_empty_careful(&uwq.wq.task_list)) {
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700513 spin_lock(&ctx->fault_pending_wqh.lock);
514 /*
515 * No need of list_del_init(), the uwq on the stack
516 * will be freed shortly anyway.
517 */
518 list_del(&uwq.wq.task_list);
519 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700520 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700521
522 /*
523 * ctx may go away after this if the userfault pseudo fd is
524 * already released.
525 */
526 userfaultfd_ctx_put(ctx);
527
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700528out:
529 return ret;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700530}
531
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800532static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
533 struct userfaultfd_wait_queue *ewq)
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800534{
Andrea Arcangeli9a69a822017-03-09 16:16:52 -0800535 if (WARN_ON_ONCE(current->flags & PF_EXITING))
536 goto out;
537
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800538 ewq->ctx = ctx;
539 init_waitqueue_entry(&ewq->wq, current);
540
541 spin_lock(&ctx->event_wqh.lock);
542 /*
543 * After the __add_wait_queue the uwq is visible to userland
544 * through poll/read().
545 */
546 __add_wait_queue(&ctx->event_wqh, &ewq->wq);
547 for (;;) {
548 set_current_state(TASK_KILLABLE);
549 if (ewq->msg.event == 0)
550 break;
551 if (ACCESS_ONCE(ctx->released) ||
552 fatal_signal_pending(current)) {
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800553 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
Mike Rapoport7eb76d42017-03-09 16:17:09 -0800554 if (ewq->msg.event == UFFD_EVENT_FORK) {
555 struct userfaultfd_ctx *new;
556
557 new = (struct userfaultfd_ctx *)
558 (unsigned long)
559 ewq->msg.arg.reserved.reserved1;
560
561 userfaultfd_ctx_put(new);
562 }
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800563 break;
564 }
565
566 spin_unlock(&ctx->event_wqh.lock);
567
568 wake_up_poll(&ctx->fd_wqh, POLLIN);
569 schedule();
570
571 spin_lock(&ctx->event_wqh.lock);
572 }
573 __set_current_state(TASK_RUNNING);
574 spin_unlock(&ctx->event_wqh.lock);
575
576 /*
577 * ctx may go away after this if the userfault pseudo fd is
578 * already released.
579 */
Andrea Arcangeli9a69a822017-03-09 16:16:52 -0800580out:
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800581 userfaultfd_ctx_put(ctx);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800582}
583
584static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
585 struct userfaultfd_wait_queue *ewq)
586{
587 ewq->msg.event = 0;
588 wake_up_locked(&ctx->event_wqh);
589 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
590}
591
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800592int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
593{
594 struct userfaultfd_ctx *ctx = NULL, *octx;
595 struct userfaultfd_fork_ctx *fctx;
596
597 octx = vma->vm_userfaultfd_ctx.ctx;
598 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
599 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
600 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
601 return 0;
602 }
603
604 list_for_each_entry(fctx, fcs, list)
605 if (fctx->orig == octx) {
606 ctx = fctx->new;
607 break;
608 }
609
610 if (!ctx) {
611 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL);
612 if (!fctx)
613 return -ENOMEM;
614
615 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
616 if (!ctx) {
617 kfree(fctx);
618 return -ENOMEM;
619 }
620
621 atomic_set(&ctx->refcount, 1);
622 ctx->flags = octx->flags;
623 ctx->state = UFFD_STATE_RUNNING;
624 ctx->features = octx->features;
625 ctx->released = false;
626 ctx->mm = vma->vm_mm;
Mike Rapoportd3aadc82017-02-22 15:42:30 -0800627 atomic_inc(&ctx->mm->mm_count);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800628
629 userfaultfd_ctx_get(octx);
630 fctx->orig = octx;
631 fctx->new = ctx;
632 list_add_tail(&fctx->list, fcs);
633 }
634
635 vma->vm_userfaultfd_ctx.ctx = ctx;
636 return 0;
637}
638
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800639static void dup_fctx(struct userfaultfd_fork_ctx *fctx)
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800640{
641 struct userfaultfd_ctx *ctx = fctx->orig;
642 struct userfaultfd_wait_queue ewq;
643
644 msg_init(&ewq.msg);
645
646 ewq.msg.event = UFFD_EVENT_FORK;
647 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new;
648
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800649 userfaultfd_event_wait_completion(ctx, &ewq);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800650}
651
652void dup_userfaultfd_complete(struct list_head *fcs)
653{
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800654 struct userfaultfd_fork_ctx *fctx, *n;
655
656 list_for_each_entry_safe(fctx, n, fcs, list) {
Andrea Arcangeli8c9e7bb2017-03-09 16:16:54 -0800657 dup_fctx(fctx);
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800658 list_del(&fctx->list);
659 kfree(fctx);
660 }
661}
662
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800663void mremap_userfaultfd_prep(struct vm_area_struct *vma,
664 struct vm_userfaultfd_ctx *vm_ctx)
665{
666 struct userfaultfd_ctx *ctx;
667
668 ctx = vma->vm_userfaultfd_ctx.ctx;
669 if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
670 vm_ctx->ctx = ctx;
671 userfaultfd_ctx_get(ctx);
672 }
673}
674
Andrea Arcangeli90794bf2017-02-22 15:42:37 -0800675void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800676 unsigned long from, unsigned long to,
677 unsigned long len)
678{
Andrea Arcangeli90794bf2017-02-22 15:42:37 -0800679 struct userfaultfd_ctx *ctx = vm_ctx->ctx;
Pavel Emelyanov72f87652017-02-22 15:42:34 -0800680 struct userfaultfd_wait_queue ewq;
681
682 if (!ctx)
683 return;
684
685 if (to & ~PAGE_MASK) {
686 userfaultfd_ctx_put(ctx);
687 return;
688 }
689
690 msg_init(&ewq.msg);
691
692 ewq.msg.event = UFFD_EVENT_REMAP;
693 ewq.msg.arg.remap.from = from;
694 ewq.msg.arg.remap.to = to;
695 ewq.msg.arg.remap.len = len;
696
697 userfaultfd_event_wait_completion(ctx, &ewq);
698}
699
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800700bool userfaultfd_remove(struct vm_area_struct *vma,
Mike Rapoportd8119142017-02-24 14:56:02 -0800701 unsigned long start, unsigned long end)
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800702{
703 struct mm_struct *mm = vma->vm_mm;
704 struct userfaultfd_ctx *ctx;
705 struct userfaultfd_wait_queue ewq;
706
707 ctx = vma->vm_userfaultfd_ctx.ctx;
Mike Rapoportd8119142017-02-24 14:56:02 -0800708 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE))
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800709 return true;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800710
711 userfaultfd_ctx_get(ctx);
712 up_read(&mm->mmap_sem);
713
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800714 msg_init(&ewq.msg);
715
Mike Rapoportd8119142017-02-24 14:56:02 -0800716 ewq.msg.event = UFFD_EVENT_REMOVE;
717 ewq.msg.arg.remove.start = start;
718 ewq.msg.arg.remove.end = end;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800719
720 userfaultfd_event_wait_completion(ctx, &ewq);
721
Andrea Arcangeli70ccb922017-03-09 16:17:11 -0800722 return false;
Pavel Emelyanov05ce7722017-02-22 15:42:40 -0800723}
724
Mike Rapoport897ab3e2017-02-24 14:58:22 -0800725static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
726 unsigned long start, unsigned long end)
727{
728 struct userfaultfd_unmap_ctx *unmap_ctx;
729
730 list_for_each_entry(unmap_ctx, unmaps, list)
731 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
732 unmap_ctx->end == end)
733 return true;
734
735 return false;
736}
737
738int userfaultfd_unmap_prep(struct vm_area_struct *vma,
739 unsigned long start, unsigned long end,
740 struct list_head *unmaps)
741{
742 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
743 struct userfaultfd_unmap_ctx *unmap_ctx;
744 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
745
746 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
747 has_unmap_ctx(ctx, unmaps, start, end))
748 continue;
749
750 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
751 if (!unmap_ctx)
752 return -ENOMEM;
753
754 userfaultfd_ctx_get(ctx);
755 unmap_ctx->ctx = ctx;
756 unmap_ctx->start = start;
757 unmap_ctx->end = end;
758 list_add_tail(&unmap_ctx->list, unmaps);
759 }
760
761 return 0;
762}
763
764void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
765{
766 struct userfaultfd_unmap_ctx *ctx, *n;
767 struct userfaultfd_wait_queue ewq;
768
769 list_for_each_entry_safe(ctx, n, uf, list) {
770 msg_init(&ewq.msg);
771
772 ewq.msg.event = UFFD_EVENT_UNMAP;
773 ewq.msg.arg.remove.start = ctx->start;
774 ewq.msg.arg.remove.end = ctx->end;
775
776 userfaultfd_event_wait_completion(ctx->ctx, &ewq);
777
778 list_del(&ctx->list);
779 kfree(ctx);
780 }
781}
782
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700783static int userfaultfd_release(struct inode *inode, struct file *file)
784{
785 struct userfaultfd_ctx *ctx = file->private_data;
786 struct mm_struct *mm = ctx->mm;
787 struct vm_area_struct *vma, *prev;
788 /* len == 0 means wake all */
789 struct userfaultfd_wake_range range = { .len = 0, };
790 unsigned long new_flags;
791
792 ACCESS_ONCE(ctx->released) = true;
793
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700794 if (!mmget_not_zero(mm))
795 goto wakeup;
796
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700797 /*
798 * Flush page faults out of all CPUs. NOTE: all page faults
799 * must be retried without returning VM_FAULT_SIGBUS if
800 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
801 * changes while handle_userfault released the mmap_sem. So
802 * it's critical that released is set to true (above), before
803 * taking the mmap_sem for writing.
804 */
805 down_write(&mm->mmap_sem);
806 prev = NULL;
807 for (vma = mm->mmap; vma; vma = vma->vm_next) {
808 cond_resched();
809 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
810 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
811 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
812 prev = vma;
813 continue;
814 }
815 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
816 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
817 new_flags, vma->anon_vma,
818 vma->vm_file, vma->vm_pgoff,
819 vma_policy(vma),
820 NULL_VM_UFFD_CTX);
821 if (prev)
822 vma = prev;
823 else
824 prev = vma;
825 vma->vm_flags = new_flags;
826 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
827 }
828 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -0700829 mmput(mm);
830wakeup:
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700831 /*
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700832 * After no new page faults can wait on this fault_*wqh, flush
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700833 * the last page faults that may have been already waiting on
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700834 * the fault_*wqh.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700835 */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700836 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -0700837 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
838 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700839 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700840
841 wake_up_poll(&ctx->fd_wqh, POLLHUP);
842 userfaultfd_ctx_put(ctx);
843 return 0;
844}
845
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700846/* fault_pending_wqh.lock must be hold by the caller */
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800847static inline struct userfaultfd_wait_queue *find_userfault_in(
848 wait_queue_head_t *wqh)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700849{
850 wait_queue_t *wq;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700851 struct userfaultfd_wait_queue *uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700852
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800853 VM_BUG_ON(!spin_is_locked(&wqh->lock));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700854
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700855 uwq = NULL;
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800856 if (!waitqueue_active(wqh))
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700857 goto out;
858 /* walk in reverse to provide FIFO behavior to read userfaults */
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800859 wq = list_last_entry(&wqh->task_list, typeof(*wq), task_list);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700860 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
861out:
862 return uwq;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700863}
864
Pavel Emelyanov6dcc27f2017-02-22 15:42:18 -0800865static inline struct userfaultfd_wait_queue *find_userfault(
866 struct userfaultfd_ctx *ctx)
867{
868 return find_userfault_in(&ctx->fault_pending_wqh);
869}
870
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800871static inline struct userfaultfd_wait_queue *find_userfault_evt(
872 struct userfaultfd_ctx *ctx)
873{
874 return find_userfault_in(&ctx->event_wqh);
875}
876
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700877static unsigned int userfaultfd_poll(struct file *file, poll_table *wait)
878{
879 struct userfaultfd_ctx *ctx = file->private_data;
880 unsigned int ret;
881
882 poll_wait(file, &ctx->fd_wqh, wait);
883
884 switch (ctx->state) {
885 case UFFD_STATE_WAIT_API:
886 return POLLERR;
887 case UFFD_STATE_RUNNING:
Andrea Arcangeliba85c702015-09-04 15:46:41 -0700888 /*
889 * poll() never guarantees that read won't block.
890 * userfaults can be waken before they're read().
891 */
892 if (unlikely(!(file->f_flags & O_NONBLOCK)))
893 return POLLERR;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700894 /*
895 * lockless access to see if there are pending faults
896 * __pollwait last action is the add_wait_queue but
897 * the spin_unlock would allow the waitqueue_active to
898 * pass above the actual list_add inside
899 * add_wait_queue critical section. So use a full
900 * memory barrier to serialize the list_add write of
901 * add_wait_queue() with the waitqueue_active read
902 * below.
903 */
904 ret = 0;
905 smp_mb();
906 if (waitqueue_active(&ctx->fault_pending_wqh))
907 ret = POLLIN;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -0800908 else if (waitqueue_active(&ctx->event_wqh))
909 ret = POLLIN;
910
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700911 return ret;
912 default:
Andrea Arcangeli84749012017-02-22 15:42:12 -0800913 WARN_ON_ONCE(1);
914 return POLLERR;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700915 }
916}
917
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800918static const struct file_operations userfaultfd_fops;
919
920static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
921 struct userfaultfd_ctx *new,
922 struct uffd_msg *msg)
923{
924 int fd;
925 struct file *file;
926 unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS;
927
928 fd = get_unused_fd_flags(flags);
929 if (fd < 0)
930 return fd;
931
932 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new,
933 O_RDWR | flags);
934 if (IS_ERR(file)) {
935 put_unused_fd(fd);
936 return PTR_ERR(file);
937 }
938
939 fd_install(fd, file);
940 msg->arg.reserved.reserved1 = 0;
941 msg->arg.fork.ufd = fd;
942
943 return 0;
944}
945
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700946static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
Andrea Arcangelia9b85f92015-09-04 15:46:37 -0700947 struct uffd_msg *msg)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700948{
949 ssize_t ret;
950 DECLARE_WAITQUEUE(wait, current);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700951 struct userfaultfd_wait_queue *uwq;
Pavel Emelyanov893e26e2017-02-22 15:42:27 -0800952 /*
953 * Handling fork event requires sleeping operations, so
954 * we drop the event_wqh lock, then do these ops, then
955 * lock it back and wake up the waiter. While the lock is
956 * dropped the ewq may go away so we keep track of it
957 * carefully.
958 */
959 LIST_HEAD(fork_event);
960 struct userfaultfd_ctx *fork_nctx = NULL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700961
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700962 /* always take the fd_wqh lock before the fault_pending_wqh lock */
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700963 spin_lock(&ctx->fd_wqh.lock);
964 __add_wait_queue(&ctx->fd_wqh, &wait);
965 for (;;) {
966 set_current_state(TASK_INTERRUPTIBLE);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700967 spin_lock(&ctx->fault_pending_wqh.lock);
968 uwq = find_userfault(ctx);
969 if (uwq) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700970 /*
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -0700971 * Use a seqcount to repeat the lockless check
972 * in wake_userfault() to avoid missing
973 * wakeups because during the refile both
974 * waitqueue could become empty if this is the
975 * only userfault.
976 */
977 write_seqcount_begin(&ctx->refile_seq);
978
979 /*
Andrea Arcangeli15b726e2015-09-04 15:46:44 -0700980 * The fault_pending_wqh.lock prevents the uwq
981 * to disappear from under us.
982 *
983 * Refile this userfault from
984 * fault_pending_wqh to fault_wqh, it's not
985 * pending anymore after we read it.
986 *
987 * Use list_del() by hand (as
988 * userfaultfd_wake_function also uses
989 * list_del_init() by hand) to be sure nobody
990 * changes __remove_wait_queue() to use
991 * list_del_init() in turn breaking the
992 * !list_empty_careful() check in
993 * handle_userfault(). The uwq->wq.task_list
994 * must never be empty at any time during the
995 * refile, or the waitqueue could disappear
996 * from under us. The "wait_queue_head_t"
997 * parameter of __remove_wait_queue() is unused
998 * anyway.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -0700999 */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001000 list_del(&uwq->wq.task_list);
1001 __add_wait_queue(&ctx->fault_wqh, &uwq->wq);
1002
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001003 write_seqcount_end(&ctx->refile_seq);
1004
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001005 /* careful to always initialize msg if ret == 0 */
1006 *msg = uwq->msg;
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001007 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001008 ret = 0;
1009 break;
1010 }
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001011 spin_unlock(&ctx->fault_pending_wqh.lock);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001012
1013 spin_lock(&ctx->event_wqh.lock);
1014 uwq = find_userfault_evt(ctx);
1015 if (uwq) {
1016 *msg = uwq->msg;
1017
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001018 if (uwq->msg.event == UFFD_EVENT_FORK) {
1019 fork_nctx = (struct userfaultfd_ctx *)
1020 (unsigned long)
1021 uwq->msg.arg.reserved.reserved1;
1022 list_move(&uwq->wq.task_list, &fork_event);
1023 spin_unlock(&ctx->event_wqh.lock);
1024 ret = 0;
1025 break;
1026 }
1027
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001028 userfaultfd_event_complete(ctx, uwq);
1029 spin_unlock(&ctx->event_wqh.lock);
1030 ret = 0;
1031 break;
1032 }
1033 spin_unlock(&ctx->event_wqh.lock);
1034
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001035 if (signal_pending(current)) {
1036 ret = -ERESTARTSYS;
1037 break;
1038 }
1039 if (no_wait) {
1040 ret = -EAGAIN;
1041 break;
1042 }
1043 spin_unlock(&ctx->fd_wqh.lock);
1044 schedule();
1045 spin_lock(&ctx->fd_wqh.lock);
1046 }
1047 __remove_wait_queue(&ctx->fd_wqh, &wait);
1048 __set_current_state(TASK_RUNNING);
1049 spin_unlock(&ctx->fd_wqh.lock);
1050
Pavel Emelyanov893e26e2017-02-22 15:42:27 -08001051 if (!ret && msg->event == UFFD_EVENT_FORK) {
1052 ret = resolve_userfault_fork(ctx, fork_nctx, msg);
1053
1054 if (!ret) {
1055 spin_lock(&ctx->event_wqh.lock);
1056 if (!list_empty(&fork_event)) {
1057 uwq = list_first_entry(&fork_event,
1058 typeof(*uwq),
1059 wq.task_list);
1060 list_del(&uwq->wq.task_list);
1061 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
1062 userfaultfd_event_complete(ctx, uwq);
1063 }
1064 spin_unlock(&ctx->event_wqh.lock);
1065 }
1066 }
1067
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001068 return ret;
1069}
1070
1071static ssize_t userfaultfd_read(struct file *file, char __user *buf,
1072 size_t count, loff_t *ppos)
1073{
1074 struct userfaultfd_ctx *ctx = file->private_data;
1075 ssize_t _ret, ret = 0;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001076 struct uffd_msg msg;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001077 int no_wait = file->f_flags & O_NONBLOCK;
1078
1079 if (ctx->state == UFFD_STATE_WAIT_API)
1080 return -EINVAL;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001081
1082 for (;;) {
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001083 if (count < sizeof(msg))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001084 return ret ? ret : -EINVAL;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001085 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001086 if (_ret < 0)
1087 return ret ? ret : _ret;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001088 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001089 return ret ? ret : -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001090 ret += sizeof(msg);
1091 buf += sizeof(msg);
1092 count -= sizeof(msg);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001093 /*
1094 * Allow to read more than one fault at time but only
1095 * block if waiting for the very first one.
1096 */
1097 no_wait = O_NONBLOCK;
1098 }
1099}
1100
1101static void __wake_userfault(struct userfaultfd_ctx *ctx,
1102 struct userfaultfd_wake_range *range)
1103{
1104 unsigned long start, end;
1105
1106 start = range->start;
1107 end = range->start + range->len;
1108
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001109 spin_lock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001110 /* wake all in the range and autoremove */
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001111 if (waitqueue_active(&ctx->fault_pending_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001112 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001113 range);
1114 if (waitqueue_active(&ctx->fault_wqh))
Andrea Arcangeliac5be6b2015-09-22 14:58:49 -07001115 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001116 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001117}
1118
1119static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1120 struct userfaultfd_wake_range *range)
1121{
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001122 unsigned seq;
1123 bool need_wakeup;
1124
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001125 /*
1126 * To be sure waitqueue_active() is not reordered by the CPU
1127 * before the pagetable update, use an explicit SMP memory
1128 * barrier here. PT lock release or up_read(mmap_sem) still
1129 * have release semantics that can allow the
1130 * waitqueue_active() to be reordered before the pte update.
1131 */
1132 smp_mb();
1133
1134 /*
1135 * Use waitqueue_active because it's very frequent to
1136 * change the address space atomically even if there are no
1137 * userfaults yet. So we take the spinlock only when we're
1138 * sure we've userfaults to wake.
1139 */
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001140 do {
1141 seq = read_seqcount_begin(&ctx->refile_seq);
1142 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1143 waitqueue_active(&ctx->fault_wqh);
1144 cond_resched();
1145 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1146 if (need_wakeup)
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001147 __wake_userfault(ctx, range);
1148}
1149
1150static __always_inline int validate_range(struct mm_struct *mm,
1151 __u64 start, __u64 len)
1152{
1153 __u64 task_size = mm->task_size;
1154
1155 if (start & ~PAGE_MASK)
1156 return -EINVAL;
1157 if (len & ~PAGE_MASK)
1158 return -EINVAL;
1159 if (!len)
1160 return -EINVAL;
1161 if (start < mmap_min_addr)
1162 return -EINVAL;
1163 if (start >= task_size)
1164 return -EINVAL;
1165 if (len > task_size - start)
1166 return -EINVAL;
1167 return 0;
1168}
1169
Mike Rapoportba6907d2017-02-22 15:43:22 -08001170static inline bool vma_can_userfault(struct vm_area_struct *vma)
1171{
Mike Rapoportcac67322017-02-22 15:43:40 -08001172 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
1173 vma_is_shmem(vma);
Mike Rapoportba6907d2017-02-22 15:43:22 -08001174}
1175
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001176static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1177 unsigned long arg)
1178{
1179 struct mm_struct *mm = ctx->mm;
1180 struct vm_area_struct *vma, *prev, *cur;
1181 int ret;
1182 struct uffdio_register uffdio_register;
1183 struct uffdio_register __user *user_uffdio_register;
1184 unsigned long vm_flags, new_flags;
1185 bool found;
Mike Rapoportcac67322017-02-22 15:43:40 -08001186 bool non_anon_pages;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001187 unsigned long start, end, vma_end;
1188
1189 user_uffdio_register = (struct uffdio_register __user *) arg;
1190
1191 ret = -EFAULT;
1192 if (copy_from_user(&uffdio_register, user_uffdio_register,
1193 sizeof(uffdio_register)-sizeof(__u64)))
1194 goto out;
1195
1196 ret = -EINVAL;
1197 if (!uffdio_register.mode)
1198 goto out;
1199 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
1200 UFFDIO_REGISTER_MODE_WP))
1201 goto out;
1202 vm_flags = 0;
1203 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1204 vm_flags |= VM_UFFD_MISSING;
1205 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
1206 vm_flags |= VM_UFFD_WP;
1207 /*
1208 * FIXME: remove the below error constraint by
1209 * implementing the wprotect tracking mode.
1210 */
1211 ret = -EINVAL;
1212 goto out;
1213 }
1214
1215 ret = validate_range(mm, uffdio_register.range.start,
1216 uffdio_register.range.len);
1217 if (ret)
1218 goto out;
1219
1220 start = uffdio_register.range.start;
1221 end = start + uffdio_register.range.len;
1222
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001223 ret = -ENOMEM;
1224 if (!mmget_not_zero(mm))
1225 goto out;
1226
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001227 down_write(&mm->mmap_sem);
1228 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001229 if (!vma)
1230 goto out_unlock;
1231
1232 /* check that there's at least one vma in the range */
1233 ret = -EINVAL;
1234 if (vma->vm_start >= end)
1235 goto out_unlock;
1236
1237 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001238 * If the first vma contains huge pages, make sure start address
1239 * is aligned to huge page size.
1240 */
1241 if (is_vm_hugetlb_page(vma)) {
1242 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1243
1244 if (start & (vma_hpagesize - 1))
1245 goto out_unlock;
1246 }
1247
1248 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001249 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001250 */
1251 found = false;
Mike Rapoportcac67322017-02-22 15:43:40 -08001252 non_anon_pages = false;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001253 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1254 cond_resched();
1255
1256 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1257 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1258
1259 /* check not compatible vmas */
1260 ret = -EINVAL;
Mike Rapoportba6907d2017-02-22 15:43:22 -08001261 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001262 goto out_unlock;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001263 /*
1264 * If this vma contains ending address, and huge pages
1265 * check alignment.
1266 */
1267 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1268 end > cur->vm_start) {
1269 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1270
1271 ret = -EINVAL;
1272
1273 if (end & (vma_hpagesize - 1))
1274 goto out_unlock;
1275 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001276
1277 /*
1278 * Check that this vma isn't already owned by a
1279 * different userfaultfd. We can't allow more than one
1280 * userfaultfd to own a single vma simultaneously or we
1281 * wouldn't know which one to deliver the userfaults to.
1282 */
1283 ret = -EBUSY;
1284 if (cur->vm_userfaultfd_ctx.ctx &&
1285 cur->vm_userfaultfd_ctx.ctx != ctx)
1286 goto out_unlock;
1287
Mike Kravetzcab350a2017-02-22 15:43:04 -08001288 /*
1289 * Note vmas containing huge pages
1290 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001291 if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur))
1292 non_anon_pages = true;
Mike Kravetzcab350a2017-02-22 15:43:04 -08001293
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001294 found = true;
1295 }
1296 BUG_ON(!found);
1297
1298 if (vma->vm_start < start)
1299 prev = vma;
1300
1301 ret = 0;
1302 do {
1303 cond_resched();
1304
Mike Rapoportba6907d2017-02-22 15:43:22 -08001305 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001306 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1307 vma->vm_userfaultfd_ctx.ctx != ctx);
1308
1309 /*
1310 * Nothing to do: this vma is already registered into this
1311 * userfaultfd and with the right tracking mode too.
1312 */
1313 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1314 (vma->vm_flags & vm_flags) == vm_flags)
1315 goto skip;
1316
1317 if (vma->vm_start > start)
1318 start = vma->vm_start;
1319 vma_end = min(end, vma->vm_end);
1320
1321 new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
1322 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1323 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1324 vma_policy(vma),
1325 ((struct vm_userfaultfd_ctx){ ctx }));
1326 if (prev) {
1327 vma = prev;
1328 goto next;
1329 }
1330 if (vma->vm_start < start) {
1331 ret = split_vma(mm, vma, start, 1);
1332 if (ret)
1333 break;
1334 }
1335 if (vma->vm_end > end) {
1336 ret = split_vma(mm, vma, end, 0);
1337 if (ret)
1338 break;
1339 }
1340 next:
1341 /*
1342 * In the vma_merge() successful mprotect-like case 8:
1343 * the next vma was merged into the current one and
1344 * the current one has not been updated yet.
1345 */
1346 vma->vm_flags = new_flags;
1347 vma->vm_userfaultfd_ctx.ctx = ctx;
1348
1349 skip:
1350 prev = vma;
1351 start = vma->vm_end;
1352 vma = vma->vm_next;
1353 } while (vma && vma->vm_start < end);
1354out_unlock:
1355 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001356 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001357 if (!ret) {
1358 /*
1359 * Now that we scanned all vmas we can already tell
1360 * userland which ioctls methods are guaranteed to
1361 * succeed on this range.
1362 */
Mike Rapoportcac67322017-02-22 15:43:40 -08001363 if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC :
Mike Kravetzcab350a2017-02-22 15:43:04 -08001364 UFFD_API_RANGE_IOCTLS,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001365 &user_uffdio_register->ioctls))
1366 ret = -EFAULT;
1367 }
1368out:
1369 return ret;
1370}
1371
1372static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1373 unsigned long arg)
1374{
1375 struct mm_struct *mm = ctx->mm;
1376 struct vm_area_struct *vma, *prev, *cur;
1377 int ret;
1378 struct uffdio_range uffdio_unregister;
1379 unsigned long new_flags;
1380 bool found;
1381 unsigned long start, end, vma_end;
1382 const void __user *buf = (void __user *)arg;
1383
1384 ret = -EFAULT;
1385 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1386 goto out;
1387
1388 ret = validate_range(mm, uffdio_unregister.start,
1389 uffdio_unregister.len);
1390 if (ret)
1391 goto out;
1392
1393 start = uffdio_unregister.start;
1394 end = start + uffdio_unregister.len;
1395
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001396 ret = -ENOMEM;
1397 if (!mmget_not_zero(mm))
1398 goto out;
1399
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001400 down_write(&mm->mmap_sem);
1401 vma = find_vma_prev(mm, start, &prev);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001402 if (!vma)
1403 goto out_unlock;
1404
1405 /* check that there's at least one vma in the range */
1406 ret = -EINVAL;
1407 if (vma->vm_start >= end)
1408 goto out_unlock;
1409
1410 /*
Mike Kravetzcab350a2017-02-22 15:43:04 -08001411 * If the first vma contains huge pages, make sure start address
1412 * is aligned to huge page size.
1413 */
1414 if (is_vm_hugetlb_page(vma)) {
1415 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1416
1417 if (start & (vma_hpagesize - 1))
1418 goto out_unlock;
1419 }
1420
1421 /*
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001422 * Search for not compatible vmas.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001423 */
1424 found = false;
1425 ret = -EINVAL;
1426 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1427 cond_resched();
1428
1429 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1430 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1431
1432 /*
1433 * Check not compatible vmas, not strictly required
1434 * here as not compatible vmas cannot have an
1435 * userfaultfd_ctx registered on them, but this
1436 * provides for more strict behavior to notice
1437 * unregistration errors.
1438 */
Mike Rapoportba6907d2017-02-22 15:43:22 -08001439 if (!vma_can_userfault(cur))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001440 goto out_unlock;
1441
1442 found = true;
1443 }
1444 BUG_ON(!found);
1445
1446 if (vma->vm_start < start)
1447 prev = vma;
1448
1449 ret = 0;
1450 do {
1451 cond_resched();
1452
Mike Rapoportba6907d2017-02-22 15:43:22 -08001453 BUG_ON(!vma_can_userfault(vma));
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001454
1455 /*
1456 * Nothing to do: this vma is already registered into this
1457 * userfaultfd and with the right tracking mode too.
1458 */
1459 if (!vma->vm_userfaultfd_ctx.ctx)
1460 goto skip;
1461
1462 if (vma->vm_start > start)
1463 start = vma->vm_start;
1464 vma_end = min(end, vma->vm_end);
1465
Andrea Arcangeli09fa5292017-02-22 15:42:46 -08001466 if (userfaultfd_missing(vma)) {
1467 /*
1468 * Wake any concurrent pending userfault while
1469 * we unregister, so they will not hang
1470 * permanently and it avoids userland to call
1471 * UFFDIO_WAKE explicitly.
1472 */
1473 struct userfaultfd_wake_range range;
1474 range.start = start;
1475 range.len = vma_end - start;
1476 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1477 }
1478
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001479 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1480 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1481 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1482 vma_policy(vma),
1483 NULL_VM_UFFD_CTX);
1484 if (prev) {
1485 vma = prev;
1486 goto next;
1487 }
1488 if (vma->vm_start < start) {
1489 ret = split_vma(mm, vma, start, 1);
1490 if (ret)
1491 break;
1492 }
1493 if (vma->vm_end > end) {
1494 ret = split_vma(mm, vma, end, 0);
1495 if (ret)
1496 break;
1497 }
1498 next:
1499 /*
1500 * In the vma_merge() successful mprotect-like case 8:
1501 * the next vma was merged into the current one and
1502 * the current one has not been updated yet.
1503 */
1504 vma->vm_flags = new_flags;
1505 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1506
1507 skip:
1508 prev = vma;
1509 start = vma->vm_end;
1510 vma = vma->vm_next;
1511 } while (vma && vma->vm_start < end);
1512out_unlock:
1513 up_write(&mm->mmap_sem);
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001514 mmput(mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001515out:
1516 return ret;
1517}
1518
1519/*
Andrea Arcangeliba85c702015-09-04 15:46:41 -07001520 * userfaultfd_wake may be used in combination with the
1521 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001522 */
1523static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1524 unsigned long arg)
1525{
1526 int ret;
1527 struct uffdio_range uffdio_wake;
1528 struct userfaultfd_wake_range range;
1529 const void __user *buf = (void __user *)arg;
1530
1531 ret = -EFAULT;
1532 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1533 goto out;
1534
1535 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
1536 if (ret)
1537 goto out;
1538
1539 range.start = uffdio_wake.start;
1540 range.len = uffdio_wake.len;
1541
1542 /*
1543 * len == 0 means wake all and we don't want to wake all here,
1544 * so check it again to be sure.
1545 */
1546 VM_BUG_ON(!range.len);
1547
1548 wake_userfault(ctx, &range);
1549 ret = 0;
1550
1551out:
1552 return ret;
1553}
1554
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001555static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1556 unsigned long arg)
1557{
1558 __s64 ret;
1559 struct uffdio_copy uffdio_copy;
1560 struct uffdio_copy __user *user_uffdio_copy;
1561 struct userfaultfd_wake_range range;
1562
1563 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1564
1565 ret = -EFAULT;
1566 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1567 /* don't copy "copy" last field */
1568 sizeof(uffdio_copy)-sizeof(__s64)))
1569 goto out;
1570
1571 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
1572 if (ret)
1573 goto out;
1574 /*
1575 * double check for wraparound just in case. copy_from_user()
1576 * will later check uffdio_copy.src + uffdio_copy.len to fit
1577 * in the userland range.
1578 */
1579 ret = -EINVAL;
1580 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
1581 goto out;
1582 if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
1583 goto out;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001584 if (mmget_not_zero(ctx->mm)) {
1585 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
1586 uffdio_copy.len);
1587 mmput(ctx->mm);
Mike Rapoport96333182017-02-24 14:58:31 -08001588 } else {
1589 return -ENOSPC;
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001590 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001591 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1592 return -EFAULT;
1593 if (ret < 0)
1594 goto out;
1595 BUG_ON(!ret);
1596 /* len == 0 would wake all */
1597 range.len = ret;
1598 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1599 range.start = uffdio_copy.dst;
1600 wake_userfault(ctx, &range);
1601 }
1602 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1603out:
1604 return ret;
1605}
1606
1607static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1608 unsigned long arg)
1609{
1610 __s64 ret;
1611 struct uffdio_zeropage uffdio_zeropage;
1612 struct uffdio_zeropage __user *user_uffdio_zeropage;
1613 struct userfaultfd_wake_range range;
1614
1615 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1616
1617 ret = -EFAULT;
1618 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1619 /* don't copy "zeropage" last field */
1620 sizeof(uffdio_zeropage)-sizeof(__s64)))
1621 goto out;
1622
1623 ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
1624 uffdio_zeropage.range.len);
1625 if (ret)
1626 goto out;
1627 ret = -EINVAL;
1628 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1629 goto out;
1630
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001631 if (mmget_not_zero(ctx->mm)) {
1632 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
1633 uffdio_zeropage.range.len);
1634 mmput(ctx->mm);
1635 }
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001636 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1637 return -EFAULT;
1638 if (ret < 0)
1639 goto out;
1640 /* len == 0 would wake all */
1641 BUG_ON(!ret);
1642 range.len = ret;
1643 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1644 range.start = uffdio_zeropage.range.start;
1645 wake_userfault(ctx, &range);
1646 }
1647 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1648out:
1649 return ret;
1650}
1651
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001652static inline unsigned int uffd_ctx_features(__u64 user_features)
1653{
1654 /*
1655 * For the current set of features the bits just coincide
1656 */
1657 return (unsigned int)user_features;
1658}
1659
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001660/*
1661 * userland asks for a certain API version and we return which bits
1662 * and ioctl commands are implemented in this kernel for such API
1663 * version or -EINVAL if unknown.
1664 */
1665static int userfaultfd_api(struct userfaultfd_ctx *ctx,
1666 unsigned long arg)
1667{
1668 struct uffdio_api uffdio_api;
1669 void __user *buf = (void __user *)arg;
1670 int ret;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001671 __u64 features;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001672
1673 ret = -EINVAL;
1674 if (ctx->state != UFFD_STATE_WAIT_API)
1675 goto out;
1676 ret = -EFAULT;
Andrea Arcangelia9b85f92015-09-04 15:46:37 -07001677 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001678 goto out;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001679 features = uffdio_api.features;
1680 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001681 memset(&uffdio_api, 0, sizeof(uffdio_api));
1682 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1683 goto out;
1684 ret = -EINVAL;
1685 goto out;
1686 }
Andrea Arcangeli65603142017-02-22 15:42:24 -08001687 /* report all available features and ioctls to userland */
1688 uffdio_api.features = UFFD_API_FEATURES;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001689 uffdio_api.ioctls = UFFD_API_IOCTLS;
1690 ret = -EFAULT;
1691 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1692 goto out;
1693 ctx->state = UFFD_STATE_RUNNING;
Andrea Arcangeli65603142017-02-22 15:42:24 -08001694 /* only enable the requested features for this uffd context */
1695 ctx->features = uffd_ctx_features(features);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001696 ret = 0;
1697out:
1698 return ret;
1699}
1700
1701static long userfaultfd_ioctl(struct file *file, unsigned cmd,
1702 unsigned long arg)
1703{
1704 int ret = -EINVAL;
1705 struct userfaultfd_ctx *ctx = file->private_data;
1706
Andrea Arcangelie6485a42015-09-04 15:47:15 -07001707 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
1708 return -EINVAL;
1709
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001710 switch(cmd) {
1711 case UFFDIO_API:
1712 ret = userfaultfd_api(ctx, arg);
1713 break;
1714 case UFFDIO_REGISTER:
1715 ret = userfaultfd_register(ctx, arg);
1716 break;
1717 case UFFDIO_UNREGISTER:
1718 ret = userfaultfd_unregister(ctx, arg);
1719 break;
1720 case UFFDIO_WAKE:
1721 ret = userfaultfd_wake(ctx, arg);
1722 break;
Andrea Arcangeliad465ca2015-09-04 15:47:11 -07001723 case UFFDIO_COPY:
1724 ret = userfaultfd_copy(ctx, arg);
1725 break;
1726 case UFFDIO_ZEROPAGE:
1727 ret = userfaultfd_zeropage(ctx, arg);
1728 break;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001729 }
1730 return ret;
1731}
1732
1733#ifdef CONFIG_PROC_FS
1734static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
1735{
1736 struct userfaultfd_ctx *ctx = f->private_data;
1737 wait_queue_t *wq;
1738 struct userfaultfd_wait_queue *uwq;
1739 unsigned long pending = 0, total = 0;
1740
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001741 spin_lock(&ctx->fault_pending_wqh.lock);
1742 list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) {
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001743 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001744 pending++;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001745 total++;
1746 }
Andrea Arcangeli15b726e2015-09-04 15:46:44 -07001747 list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) {
1748 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
1749 total++;
1750 }
1751 spin_unlock(&ctx->fault_pending_wqh.lock);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001752
1753 /*
1754 * If more protocols will be added, there will be all shown
1755 * separated by a space. Like this:
1756 * protocols: aa:... bb:...
1757 */
1758 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
Mike Rapoport045098e2017-04-07 16:04:42 -07001759 pending, total, UFFD_API, ctx->features,
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001760 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
1761}
1762#endif
1763
1764static const struct file_operations userfaultfd_fops = {
1765#ifdef CONFIG_PROC_FS
1766 .show_fdinfo = userfaultfd_show_fdinfo,
1767#endif
1768 .release = userfaultfd_release,
1769 .poll = userfaultfd_poll,
1770 .read = userfaultfd_read,
1771 .unlocked_ioctl = userfaultfd_ioctl,
1772 .compat_ioctl = userfaultfd_ioctl,
1773 .llseek = noop_llseek,
1774};
1775
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001776static void init_once_userfaultfd_ctx(void *mem)
1777{
1778 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
1779
1780 init_waitqueue_head(&ctx->fault_pending_wqh);
1781 init_waitqueue_head(&ctx->fault_wqh);
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001782 init_waitqueue_head(&ctx->event_wqh);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001783 init_waitqueue_head(&ctx->fd_wqh);
Andrea Arcangeli2c5b7e12015-09-04 15:47:23 -07001784 seqcount_init(&ctx->refile_seq);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001785}
1786
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001787/**
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001788 * userfaultfd_file_create - Creates a userfaultfd file pointer.
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001789 * @flags: Flags for the userfaultfd file.
1790 *
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001791 * This function creates a userfaultfd file pointer, w/out installing
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001792 * it into the fd table. This is useful when the userfaultfd file is
1793 * used during the initialization of data structures that require
1794 * extra setup after the userfaultfd creation. So the userfaultfd
1795 * creation is split into the file pointer creation phase, and the
1796 * file descriptor installation phase. In this way races with
1797 * userspace closing the newly installed file descriptor can be
Masahiro Yamada9332ef92017-02-27 14:28:47 -08001798 * avoided. Returns a userfaultfd file pointer, or a proper error
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001799 * pointer.
1800 */
1801static struct file *userfaultfd_file_create(int flags)
1802{
1803 struct file *file;
1804 struct userfaultfd_ctx *ctx;
1805
1806 BUG_ON(!current->mm);
1807
1808 /* Check the UFFD_* constants for consistency. */
1809 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1810 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1811
1812 file = ERR_PTR(-EINVAL);
1813 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
1814 goto out;
1815
1816 file = ERR_PTR(-ENOMEM);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001817 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001818 if (!ctx)
1819 goto out;
1820
1821 atomic_set(&ctx->refcount, 1);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001822 ctx->flags = flags;
Pavel Emelyanov9cd75c32017-02-22 15:42:21 -08001823 ctx->features = 0;
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001824 ctx->state = UFFD_STATE_WAIT_API;
1825 ctx->released = false;
1826 ctx->mm = current->mm;
1827 /* prevent the mm struct to be freed */
Vegard Nossumf1f10072017-02-27 14:30:07 -08001828 mmgrab(ctx->mm);
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001829
1830 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
1831 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
Eric Biggersc03e9462015-09-17 16:01:54 -07001832 if (IS_ERR(file)) {
Oleg Nesterovd2005e32016-05-20 16:58:36 -07001833 mmdrop(ctx->mm);
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001834 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
Eric Biggersc03e9462015-09-17 16:01:54 -07001835 }
Andrea Arcangeli86039bd2015-09-04 15:46:31 -07001836out:
1837 return file;
1838}
1839
1840SYSCALL_DEFINE1(userfaultfd, int, flags)
1841{
1842 int fd, error;
1843 struct file *file;
1844
1845 error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
1846 if (error < 0)
1847 return error;
1848 fd = error;
1849
1850 file = userfaultfd_file_create(flags);
1851 if (IS_ERR(file)) {
1852 error = PTR_ERR(file);
1853 goto err_put_unused_fd;
1854 }
1855 fd_install(fd, file);
1856
1857 return fd;
1858
1859err_put_unused_fd:
1860 put_unused_fd(fd);
1861
1862 return error;
1863}
Andrea Arcangeli3004ec92015-09-04 15:46:48 -07001864
1865static int __init userfaultfd_init(void)
1866{
1867 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
1868 sizeof(struct userfaultfd_ctx),
1869 0,
1870 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
1871 init_once_userfaultfd_ctx);
1872 return 0;
1873}
1874__initcall(userfaultfd_init);