path: root/fs
diff options
authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2015-02-11 15:27:31 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-04-29 10:31:56 +0200
commit3b09542675a042106bd31a84b7c86b181751d029 (patch)
tree9b7efa4c69791367a66db36bf65987d86fc31efd /fs
parent620d77bda9fedb4dcd1271d3cbcbe099dff01f98 (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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 06d8c689a316..eaa7374305a3 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -993,7 +993,7 @@ 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' */
@@ -1054,15 +1054,19 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
/* 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)