Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf
[linux-2.6-microblaze.git] / mm / userfaultfd.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  mm/userfaultfd.c
4  *
5  *  Copyright (C) 2015  Red Hat, Inc.
6  */
7
8 #include <linux/mm.h>
9 #include <linux/sched/signal.h>
10 #include <linux/pagemap.h>
11 #include <linux/rmap.h>
12 #include <linux/swap.h>
13 #include <linux/swapops.h>
14 #include <linux/userfaultfd_k.h>
15 #include <linux/mmu_notifier.h>
16 #include <linux/hugetlb.h>
17 #include <linux/shmem_fs.h>
18 #include <asm/tlbflush.h>
19 #include "internal.h"
20
21 static int mcopy_atomic_pte(struct mm_struct *dst_mm,
22                             pmd_t *dst_pmd,
23                             struct vm_area_struct *dst_vma,
24                             unsigned long dst_addr,
25                             unsigned long src_addr,
26                             struct page **pagep)
27 {
28         struct mem_cgroup *memcg;
29         pte_t _dst_pte, *dst_pte;
30         spinlock_t *ptl;
31         void *page_kaddr;
32         int ret;
33         struct page *page;
34         pgoff_t offset, max_off;
35         struct inode *inode;
36
37         if (!*pagep) {
38                 ret = -ENOMEM;
39                 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, dst_vma, dst_addr);
40                 if (!page)
41                         goto out;
42
43                 page_kaddr = kmap_atomic(page);
44                 ret = copy_from_user(page_kaddr,
45                                      (const void __user *) src_addr,
46                                      PAGE_SIZE);
47                 kunmap_atomic(page_kaddr);
48
49                 /* fallback to copy_from_user outside mmap_sem */
50                 if (unlikely(ret)) {
51                         ret = -ENOENT;
52                         *pagep = page;
53                         /* don't free the page */
54                         goto out;
55                 }
56         } else {
57                 page = *pagep;
58                 *pagep = NULL;
59         }
60
61         /*
62          * The memory barrier inside __SetPageUptodate makes sure that
63          * preceeding stores to the page contents become visible before
64          * the set_pte_at() write.
65          */
66         __SetPageUptodate(page);
67
68         ret = -ENOMEM;
69         if (mem_cgroup_try_charge(page, dst_mm, GFP_KERNEL, &memcg, false))
70                 goto out_release;
71
72         _dst_pte = mk_pte(page, dst_vma->vm_page_prot);
73         if (dst_vma->vm_flags & VM_WRITE)
74                 _dst_pte = pte_mkwrite(pte_mkdirty(_dst_pte));
75
76         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
77         if (dst_vma->vm_file) {
78                 /* the shmem MAP_PRIVATE case requires checking the i_size */
79                 inode = dst_vma->vm_file->f_inode;
80                 offset = linear_page_index(dst_vma, dst_addr);
81                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
82                 ret = -EFAULT;
83                 if (unlikely(offset >= max_off))
84                         goto out_release_uncharge_unlock;
85         }
86         ret = -EEXIST;
87         if (!pte_none(*dst_pte))
88                 goto out_release_uncharge_unlock;
89
90         inc_mm_counter(dst_mm, MM_ANONPAGES);
91         page_add_new_anon_rmap(page, dst_vma, dst_addr, false);
92         mem_cgroup_commit_charge(page, memcg, false, false);
93         lru_cache_add_active_or_unevictable(page, dst_vma);
94
95         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
96
97         /* No need to invalidate - it was non-present before */
98         update_mmu_cache(dst_vma, dst_addr, dst_pte);
99
100         pte_unmap_unlock(dst_pte, ptl);
101         ret = 0;
102 out:
103         return ret;
104 out_release_uncharge_unlock:
105         pte_unmap_unlock(dst_pte, ptl);
106         mem_cgroup_cancel_charge(page, memcg, false);
107 out_release:
108         put_page(page);
109         goto out;
110 }
111
112 static int mfill_zeropage_pte(struct mm_struct *dst_mm,
113                               pmd_t *dst_pmd,
114                               struct vm_area_struct *dst_vma,
115                               unsigned long dst_addr)
116 {
117         pte_t _dst_pte, *dst_pte;
118         spinlock_t *ptl;
119         int ret;
120         pgoff_t offset, max_off;
121         struct inode *inode;
122
123         _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
124                                          dst_vma->vm_page_prot));
125         dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
126         if (dst_vma->vm_file) {
127                 /* the shmem MAP_PRIVATE case requires checking the i_size */
128                 inode = dst_vma->vm_file->f_inode;
129                 offset = linear_page_index(dst_vma, dst_addr);
130                 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
131                 ret = -EFAULT;
132                 if (unlikely(offset >= max_off))
133                         goto out_unlock;
134         }
135         ret = -EEXIST;
136         if (!pte_none(*dst_pte))
137                 goto out_unlock;
138         set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
139         /* No need to invalidate - it was non-present before */
140         update_mmu_cache(dst_vma, dst_addr, dst_pte);
141         ret = 0;
142 out_unlock:
143         pte_unmap_unlock(dst_pte, ptl);
144         return ret;
145 }
146
147 static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
148 {
149         pgd_t *pgd;
150         p4d_t *p4d;
151         pud_t *pud;
152
153         pgd = pgd_offset(mm, address);
154         p4d = p4d_alloc(mm, pgd, address);
155         if (!p4d)
156                 return NULL;
157         pud = pud_alloc(mm, p4d, address);
158         if (!pud)
159                 return NULL;
160         /*
161          * Note that we didn't run this because the pmd was
162          * missing, the *pmd may be already established and in
163          * turn it may also be a trans_huge_pmd.
164          */
165         return pmd_alloc(mm, pud, address);
166 }
167
168 #ifdef CONFIG_HUGETLB_PAGE
169 /*
170  * __mcopy_atomic processing for HUGETLB vmas.  Note that this routine is
171  * called with mmap_sem held, it will release mmap_sem before returning.
172  */
173 static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
174                                               struct vm_area_struct *dst_vma,
175                                               unsigned long dst_start,
176                                               unsigned long src_start,
177                                               unsigned long len,
178                                               bool zeropage)
179 {
180         int vm_alloc_shared = dst_vma->vm_flags & VM_SHARED;
181         int vm_shared = dst_vma->vm_flags & VM_SHARED;
182         ssize_t err;
183         pte_t *dst_pte;
184         unsigned long src_addr, dst_addr;
185         long copied;
186         struct page *page;
187         struct hstate *h;
188         unsigned long vma_hpagesize;
189         pgoff_t idx;
190         u32 hash;
191         struct address_space *mapping;
192
193         /*
194          * There is no default zero huge page for all huge page sizes as
195          * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
196          * by THP.  Since we can not reliably insert a zero page, this
197          * feature is not supported.
198          */
199         if (zeropage) {
200                 up_read(&dst_mm->mmap_sem);
201                 return -EINVAL;
202         }
203
204         src_addr = src_start;
205         dst_addr = dst_start;
206         copied = 0;
207         page = NULL;
208         vma_hpagesize = vma_kernel_pagesize(dst_vma);
209
210         /*
211          * Validate alignment based on huge page size
212          */
213         err = -EINVAL;
214         if (dst_start & (vma_hpagesize - 1) || len & (vma_hpagesize - 1))
215                 goto out_unlock;
216
217 retry:
218         /*
219          * On routine entry dst_vma is set.  If we had to drop mmap_sem and
220          * retry, dst_vma will be set to NULL and we must lookup again.
221          */
222         if (!dst_vma) {
223                 err = -ENOENT;
224                 dst_vma = find_vma(dst_mm, dst_start);
225                 if (!dst_vma || !is_vm_hugetlb_page(dst_vma))
226                         goto out_unlock;
227                 /*
228                  * Check the vma is registered in uffd, this is
229                  * required to enforce the VM_MAYWRITE check done at
230                  * uffd registration time.
231                  */
232                 if (!dst_vma->vm_userfaultfd_ctx.ctx)
233                         goto out_unlock;
234
235                 if (dst_start < dst_vma->vm_start ||
236                     dst_start + len > dst_vma->vm_end)
237                         goto out_unlock;
238
239                 err = -EINVAL;
240                 if (vma_hpagesize != vma_kernel_pagesize(dst_vma))
241                         goto out_unlock;
242
243                 vm_shared = dst_vma->vm_flags & VM_SHARED;
244         }
245
246         if (WARN_ON(dst_addr & (vma_hpagesize - 1) ||
247                     (len - copied) & (vma_hpagesize - 1)))
248                 goto out_unlock;
249
250         /*
251          * If not shared, ensure the dst_vma has a anon_vma.
252          */
253         err = -ENOMEM;
254         if (!vm_shared) {
255                 if (unlikely(anon_vma_prepare(dst_vma)))
256                         goto out_unlock;
257         }
258
259         h = hstate_vma(dst_vma);
260
261         while (src_addr < src_start + len) {
262                 pte_t dst_pteval;
263
264                 BUG_ON(dst_addr >= dst_start + len);
265                 VM_BUG_ON(dst_addr & ~huge_page_mask(h));
266
267                 /*
268                  * Serialize via hugetlb_fault_mutex
269                  */
270                 idx = linear_page_index(dst_vma, dst_addr);
271                 mapping = dst_vma->vm_file->f_mapping;
272                 hash = hugetlb_fault_mutex_hash(h, mapping, idx, dst_addr);
273                 mutex_lock(&hugetlb_fault_mutex_table[hash]);
274
275                 err = -ENOMEM;
276                 dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
277                 if (!dst_pte) {
278                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
279                         goto out_unlock;
280                 }
281
282                 err = -EEXIST;
283                 dst_pteval = huge_ptep_get(dst_pte);
284                 if (!huge_pte_none(dst_pteval)) {
285                         mutex_unlock(&hugetlb_fault_mutex_table[hash]);
286                         goto out_unlock;
287                 }
288
289                 err = hugetlb_mcopy_atomic_pte(dst_mm, dst_pte, dst_vma,
290                                                 dst_addr, src_addr, &page);
291
292                 mutex_unlock(&hugetlb_fault_mutex_table[hash]);
293                 vm_alloc_shared = vm_shared;
294
295                 cond_resched();
296
297                 if (unlikely(err == -ENOENT)) {
298                         up_read(&dst_mm->mmap_sem);
299                         BUG_ON(!page);
300
301                         err = copy_huge_page_from_user(page,
302                                                 (const void __user *)src_addr,
303                                                 pages_per_huge_page(h), true);
304                         if (unlikely(err)) {
305                                 err = -EFAULT;
306                                 goto out;
307                         }
308                         down_read(&dst_mm->mmap_sem);
309
310                         dst_vma = NULL;
311                         goto retry;
312                 } else
313                         BUG_ON(page);
314
315                 if (!err) {
316                         dst_addr += vma_hpagesize;
317                         src_addr += vma_hpagesize;
318                         copied += vma_hpagesize;
319
320                         if (fatal_signal_pending(current))
321                                 err = -EINTR;
322                 }
323                 if (err)
324                         break;
325         }
326
327 out_unlock:
328         up_read(&dst_mm->mmap_sem);
329 out:
330         if (page) {
331                 /*
332                  * We encountered an error and are about to free a newly
333                  * allocated huge page.
334                  *
335                  * Reservation handling is very subtle, and is different for
336                  * private and shared mappings.  See the routine
337                  * restore_reserve_on_error for details.  Unfortunately, we
338                  * can not call restore_reserve_on_error now as it would
339                  * require holding mmap_sem.
340                  *
341                  * If a reservation for the page existed in the reservation
342                  * map of a private mapping, the map was modified to indicate
343                  * the reservation was consumed when the page was allocated.
344                  * We clear the PagePrivate flag now so that the global
345                  * reserve count will not be incremented in free_huge_page.
346                  * The reservation map will still indicate the reservation
347                  * was consumed and possibly prevent later page allocation.
348                  * This is better than leaking a global reservation.  If no
349                  * reservation existed, it is still safe to clear PagePrivate
350                  * as no adjustments to reservation counts were made during
351                  * allocation.
352                  *
353                  * The reservation map for shared mappings indicates which
354                  * pages have reservations.  When a huge page is allocated
355                  * for an address with a reservation, no change is made to
356                  * the reserve map.  In this case PagePrivate will be set
357                  * to indicate that the global reservation count should be
358                  * incremented when the page is freed.  This is the desired
359                  * behavior.  However, when a huge page is allocated for an
360                  * address without a reservation a reservation entry is added
361                  * to the reservation map, and PagePrivate will not be set.
362                  * When the page is freed, the global reserve count will NOT
363                  * be incremented and it will appear as though we have leaked
364                  * reserved page.  In this case, set PagePrivate so that the
365                  * global reserve count will be incremented to match the
366                  * reservation map entry which was created.
367                  *
368                  * Note that vm_alloc_shared is based on the flags of the vma
369                  * for which the page was originally allocated.  dst_vma could
370                  * be different or NULL on error.
371                  */
372                 if (vm_alloc_shared)
373                         SetPagePrivate(page);
374                 else
375                         ClearPagePrivate(page);
376                 put_page(page);
377         }
378         BUG_ON(copied < 0);
379         BUG_ON(err > 0);
380         BUG_ON(!copied && !err);
381         return copied ? copied : err;
382 }
383 #else /* !CONFIG_HUGETLB_PAGE */
384 /* fail at build time if gcc attempts to use this */
385 extern ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
386                                       struct vm_area_struct *dst_vma,
387                                       unsigned long dst_start,
388                                       unsigned long src_start,
389                                       unsigned long len,
390                                       bool zeropage);
391 #endif /* CONFIG_HUGETLB_PAGE */
392
393 static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
394                                                 pmd_t *dst_pmd,
395                                                 struct vm_area_struct *dst_vma,
396                                                 unsigned long dst_addr,
397                                                 unsigned long src_addr,
398                                                 struct page **page,
399                                                 bool zeropage)
400 {
401         ssize_t err;
402
403         /*
404          * The normal page fault path for a shmem will invoke the
405          * fault, fill the hole in the file and COW it right away. The
406          * result generates plain anonymous memory. So when we are
407          * asked to fill an hole in a MAP_PRIVATE shmem mapping, we'll
408          * generate anonymous memory directly without actually filling
409          * the hole. For the MAP_PRIVATE case the robustness check
410          * only happens in the pagetable (to verify it's still none)
411          * and not in the radix tree.
412          */
413         if (!(dst_vma->vm_flags & VM_SHARED)) {
414                 if (!zeropage)
415                         err = mcopy_atomic_pte(dst_mm, dst_pmd, dst_vma,
416                                                dst_addr, src_addr, page);
417                 else
418                         err = mfill_zeropage_pte(dst_mm, dst_pmd,
419                                                  dst_vma, dst_addr);
420         } else {
421                 if (!zeropage)
422                         err = shmem_mcopy_atomic_pte(dst_mm, dst_pmd,
423                                                      dst_vma, dst_addr,
424                                                      src_addr, page);
425                 else
426                         err = shmem_mfill_zeropage_pte(dst_mm, dst_pmd,
427                                                        dst_vma, dst_addr);
428         }
429
430         return err;
431 }
432
433 static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm,
434                                               unsigned long dst_start,
435                                               unsigned long src_start,
436                                               unsigned long len,
437                                               bool zeropage,
438                                               bool *mmap_changing)
439 {
440         struct vm_area_struct *dst_vma;
441         ssize_t err;
442         pmd_t *dst_pmd;
443         unsigned long src_addr, dst_addr;
444         long copied;
445         struct page *page;
446
447         /*
448          * Sanitize the command parameters:
449          */
450         BUG_ON(dst_start & ~PAGE_MASK);
451         BUG_ON(len & ~PAGE_MASK);
452
453         /* Does the address range wrap, or is the span zero-sized? */
454         BUG_ON(src_start + len <= src_start);
455         BUG_ON(dst_start + len <= dst_start);
456
457         src_addr = src_start;
458         dst_addr = dst_start;
459         copied = 0;
460         page = NULL;
461 retry:
462         down_read(&dst_mm->mmap_sem);
463
464         /*
465          * If memory mappings are changing because of non-cooperative
466          * operation (e.g. mremap) running in parallel, bail out and
467          * request the user to retry later
468          */
469         err = -EAGAIN;
470         if (mmap_changing && READ_ONCE(*mmap_changing))
471                 goto out_unlock;
472
473         /*
474          * Make sure the vma is not shared, that the dst range is
475          * both valid and fully within a single existing vma.
476          */
477         err = -ENOENT;
478         dst_vma = find_vma(dst_mm, dst_start);
479         if (!dst_vma)
480                 goto out_unlock;
481         /*
482          * Check the vma is registered in uffd, this is required to
483          * enforce the VM_MAYWRITE check done at uffd registration
484          * time.
485          */
486         if (!dst_vma->vm_userfaultfd_ctx.ctx)
487                 goto out_unlock;
488
489         if (dst_start < dst_vma->vm_start ||
490             dst_start + len > dst_vma->vm_end)
491                 goto out_unlock;
492
493         err = -EINVAL;
494         /*
495          * shmem_zero_setup is invoked in mmap for MAP_ANONYMOUS|MAP_SHARED but
496          * it will overwrite vm_ops, so vma_is_anonymous must return false.
497          */
498         if (WARN_ON_ONCE(vma_is_anonymous(dst_vma) &&
499             dst_vma->vm_flags & VM_SHARED))
500                 goto out_unlock;
501
502         /*
503          * If this is a HUGETLB vma, pass off to appropriate routine
504          */
505         if (is_vm_hugetlb_page(dst_vma))
506                 return  __mcopy_atomic_hugetlb(dst_mm, dst_vma, dst_start,
507                                                 src_start, len, zeropage);
508
509         if (!vma_is_anonymous(dst_vma) && !vma_is_shmem(dst_vma))
510                 goto out_unlock;
511
512         /*
513          * Ensure the dst_vma has a anon_vma or this page
514          * would get a NULL anon_vma when moved in the
515          * dst_vma.
516          */
517         err = -ENOMEM;
518         if (!(dst_vma->vm_flags & VM_SHARED) &&
519             unlikely(anon_vma_prepare(dst_vma)))
520                 goto out_unlock;
521
522         while (src_addr < src_start + len) {
523                 pmd_t dst_pmdval;
524
525                 BUG_ON(dst_addr >= dst_start + len);
526
527                 dst_pmd = mm_alloc_pmd(dst_mm, dst_addr);
528                 if (unlikely(!dst_pmd)) {
529                         err = -ENOMEM;
530                         break;
531                 }
532
533                 dst_pmdval = pmd_read_atomic(dst_pmd);
534                 /*
535                  * If the dst_pmd is mapped as THP don't
536                  * override it and just be strict.
537                  */
538                 if (unlikely(pmd_trans_huge(dst_pmdval))) {
539                         err = -EEXIST;
540                         break;
541                 }
542                 if (unlikely(pmd_none(dst_pmdval)) &&
543                     unlikely(__pte_alloc(dst_mm, dst_pmd))) {
544                         err = -ENOMEM;
545                         break;
546                 }
547                 /* If an huge pmd materialized from under us fail */
548                 if (unlikely(pmd_trans_huge(*dst_pmd))) {
549                         err = -EFAULT;
550                         break;
551                 }
552
553                 BUG_ON(pmd_none(*dst_pmd));
554                 BUG_ON(pmd_trans_huge(*dst_pmd));
555
556                 err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
557                                        src_addr, &page, zeropage);
558                 cond_resched();
559
560                 if (unlikely(err == -ENOENT)) {
561                         void *page_kaddr;
562
563                         up_read(&dst_mm->mmap_sem);
564                         BUG_ON(!page);
565
566                         page_kaddr = kmap(page);
567                         err = copy_from_user(page_kaddr,
568                                              (const void __user *) src_addr,
569                                              PAGE_SIZE);
570                         kunmap(page);
571                         if (unlikely(err)) {
572                                 err = -EFAULT;
573                                 goto out;
574                         }
575                         goto retry;
576                 } else
577                         BUG_ON(page);
578
579                 if (!err) {
580                         dst_addr += PAGE_SIZE;
581                         src_addr += PAGE_SIZE;
582                         copied += PAGE_SIZE;
583
584                         if (fatal_signal_pending(current))
585                                 err = -EINTR;
586                 }
587                 if (err)
588                         break;
589         }
590
591 out_unlock:
592         up_read(&dst_mm->mmap_sem);
593 out:
594         if (page)
595                 put_page(page);
596         BUG_ON(copied < 0);
597         BUG_ON(err > 0);
598         BUG_ON(!copied && !err);
599         return copied ? copied : err;
600 }
601
602 ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
603                      unsigned long src_start, unsigned long len,
604                      bool *mmap_changing)
605 {
606         return __mcopy_atomic(dst_mm, dst_start, src_start, len, false,
607                               mmap_changing);
608 }
609
610 ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start,
611                        unsigned long len, bool *mmap_changing)
612 {
613         return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing);
614 }