diff options
| author | Hugh Dickins <hugh@veritas.com> | 2007-02-10 01:43:00 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-11 10:51:17 -0800 |
| commit | c3704ceb4ad055b489b143f4e37c57d128908012 (patch) | |
| tree | 730892c9d4d9dbab03c77597e822a7cb79c9cd96 | |
| parent | f05b6284ee5d3be51ebe22284fc4b25fc586f380 (diff) | |
[PATCH] page_mkwrite caller race fix
After do_wp_page has tested page_mkwrite, it must release old_page after
acquiring page table lock, not before: at some stage that ordering got
reversed, leaving a (very unlikely) window in which old_page might be
truncated, freed, and reused in the same position.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/memory.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/mm/memory.c b/mm/memory.c index ef09f0acb1d8..0047d3a4e364 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1531,8 +1531,6 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, if (vma->vm_ops->page_mkwrite(vma, old_page) < 0) goto unwritable_page; - page_cache_release(old_page); - /* * Since we dropped the lock we need to revalidate * the PTE as someone else may have changed it. If @@ -1541,6 +1539,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, */ page_table = pte_offset_map_lock(mm, pmd, address, &ptl); + page_cache_release(old_page); if (!pte_same(*page_table, orig_pte)) goto unlock; } |