[31/37] mm: fix possible off-by-one in walk_pte_range()

Greg KH
2008-04-29T17:32:45Z

[-- Attachment #1: mm-fix-possible-off-by-one-in-walk_pte_range.patch --]
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2.6.25-stable review patch. If anyone has any objections, please let us
know.

------------------
From: Johannes Weiner <hannes@saeurebad.de>

commit 556637cdabcd5918c7d4a1a2679b8f86fc81e891 upstream

After the loop in walk_pte_range() pte might point to the first address after
the pmd it walks. The pte_unmap() is then applied to something bad.

Spotted by Roel Kluin and Andreas Schwab.

Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
Cc: Roel Kluin <12o3l@tiscali.nl>
Cc: Andreas Schwab <schwab@suse.de>
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Mikael Pettersson <mikpe@it.uu.se>
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@suse.de>

---
mm/pagewalk.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -9,11 +9,15 @@ static int walk_pte_range(pmd_t *pmd, un
int err = 0;

pte = pte_offset_map(pmd, addr);
- do {
+ for (;;) {
err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, private);
if (err)
break;
- } while (pte++, addr += PAGE_SIZE, addr != end);
+ addr += PAGE_SIZE;
+ if (addr == end)
+ break;
+ pte++;
+ }

pte_unmap(pte);
return err;

--