path: root/mm
diff options
authorVlastimil Babka <vbabka@suse.cz>2013-09-30 13:45:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-30 14:31:02 -0700
commiteadb41ae82f802105c0601aa8a0a0e7595826497 (patch)
treef8bb5f7f5e2ae9ed84b63548c8112eae3c8976ef /mm
parent117aad1e9e4d97448d1df3f84b08bd65811e6d6a (diff)
mm/mlock.c: prevent walking off the end of a pagetable in no-pmd configuration
The function __munlock_pagevec_fill() introduced in commit 7a8010cd3627 ("mm: munlock: manual pte walk in fast path instead of follow_page_mask()") uses pmd_addr_end() for restricting its operation within current page table. This is insufficient on architectures/configurations where pmd is folded and pmd_addr_end() just returns the end of the full range to be walked. In this case, it allows pte++ to walk off the end of a page table resulting in unpredictable behaviour. This patch fixes the function by using pgd_addr_end() and pud_addr_end() before pmd_addr_end(), which will yield correct page table boundary on all configurations. This is similar to what existing page walkers do when walking each level of the page table. Additionaly, the patch clarifies a comment for get_locked_pte() call in the function. Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: Fengguang Wu <fengguang.wu@intel.com> Reviewed-by: Bob Liu <bob.liu@oracle.com> Cc: Jörn Engel <joern@logfs.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Michel Lespinasse <walken@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 6 insertions, 2 deletions
diff --git a/mm/mlock.c b/mm/mlock.c
index 67ba6da7d0e..d480cd6fc47 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -379,10 +379,14 @@ static unsigned long __munlock_pagevec_fill(struct pagevec *pvec,
* Initialize pte walk starting at the already pinned page where we
- * are sure that there is a pte.
+ * are sure that there is a pte, as it was pinned under the same
+ * mmap_sem write op.
pte = get_locked_pte(vma->vm_mm, start, &ptl);
- end = min(end, pmd_addr_end(start, end));
+ /* Make sure we do not cross the page table boundary */
+ end = pgd_addr_end(start, end);
+ end = pud_addr_end(start, end);
+ end = pmd_addr_end(start, end);
/* The page next to the pinned page is the first we will try to get */
start += PAGE_SIZE;