diff options
| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2015-02-11 15:27:31 -0800 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-04-27 20:38:16 +0200 |
| commit | 8ead83eacb662ddb22a8e8e91b804a49ea182716 (patch) | |
| tree | 4fa9d38d0a198673374429ff1b68aaa21b9be503 | |
| parent | fdfce812d2c6bd0c1eb6ccd3196fe34b5e293c6b (diff) | |
proc/pagemap: walk page tables under pte lock
commit 05fbf357d94152171bc50f8a369390f1f16efd89 upstream.
Lockless access to pte in pagemap_pte_range() might race with page
migration and trigger BUG_ON(!PageLocked()) in migration_entry_to_page():
CPU A (pagemap) CPU B (migration)
lock_page()
try_to_unmap(page, TTU_MIGRATION...)
make_migration_entry()
set_pte_at()
<read *pte>
pte_to_pagemap_entry()
remove_migration_ptes()
unlock_page()
if(is_migration_entry())
migration_entry_to_page()
BUG_ON(!PageLocked(page))
Also lockless read might be non-atomic if pte is larger than wordsize.
Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes.
Fixes: 052fb0d635df ("proc: report file/anon bit in /proc/pid/pagemap")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reported-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: <stable@vger.kernel.org> [3.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | fs/proc/task_mmu.c | 15 |
1 files changed, 10 insertions, 5 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 6223070e7265..d20f37d1c6e7 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -996,7 +996,8 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, { struct vm_area_struct *vma; struct pagemapread *pm = walk->private; - pte_t *pte; + spinlock_t *ptl; + pte_t *pte, *orig_pte; int err = 0; /* find the first VMA at or above 'addr' */ @@ -1057,15 +1058,19 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, BUG_ON(is_vm_hugetlb_page(vma)); /* Addresses in the VMA. */ - for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) { + orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + for (; addr < min(end, vma->vm_end); pte++, addr += PAGE_SIZE) { pagemap_entry_t pme; - pte = pte_offset_map(pmd, addr); + pte_to_pagemap_entry(&pme, pm, vma, addr, *pte); - pte_unmap(pte); err = add_to_pagemap(addr, &pme, pm); if (err) - return err; + break; } + pte_unmap_unlock(orig_pte, ptl); + + if (err) + return err; if (addr == end) break; |