diff options
| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2015-02-11 15:27:31 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-11 17:06:05 -0800 |
| commit | 05fbf357d94152171bc50f8a369390f1f16efd89 (patch) | |
| tree | 656156ba6e3b055ef9353f0d17e92b59de49175b | |
| parent | 0664e57ff0c68cbca012a45a38288fa277eb6795 (diff) | |
proc/pagemap: walk page tables under pte lock
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>
| -rw-r--r-- | fs/proc/task_mmu.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index e6e0abeb5d12..eeab30fcffcc 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1056,7 +1056,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, struct vm_area_struct *vma; struct pagemapread *pm = walk->private; spinlock_t *ptl; - pte_t *pte; + pte_t *pte, *orig_pte; int err = 0; /* find the first VMA at or above 'addr' */ @@ -1117,15 +1117,19 @@ 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; |