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authorAndrea Arcangeli <aarcange@redhat.com>2011-10-31 17:08:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-10-31 17:30:47 -0700
commitebed48460be5abd86d9a24fa7c66378e58109f30 (patch)
tree721d935953c58ac014e3d00ea1092ab480ea3356 /mm/mremap.c
parent6661672053aee709d93f5dbd7887c789364c11d4 (diff)
downloadlinaro-lsk-ebed48460be5abd86d9a24fa7c66378e58109f30.tar.gz
mremap: check for overflow using deltas
Using "- 1" relies on the old_end to be page aligned and PAGE_SIZE > 1, those are reasonable requirements but the check remains obscure and it looks more like an off by one error than an overflow check. This I feel will improve readability. Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Acked-by: Johannes Weiner <jweiner@redhat.com> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mremap.c')
-rw-r--r--mm/mremap.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 506fa44403d..195e866568e 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -141,9 +141,10 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
cond_resched();
next = (old_addr + PMD_SIZE) & PMD_MASK;
- if (next - 1 > old_end)
- next = old_end;
+ /* even if next overflowed, extent below will be ok */
extent = next - old_addr;
+ if (extent > old_end - old_addr)
+ extent = old_end - old_addr;
old_pmd = get_old_pmd(vma->vm_mm, old_addr);
if (!old_pmd)
continue;