Messages in this thread Patch in this message | | | From | Johannes Weiner <> | Subject | [PATCH] mm: Fix possible off-by-one in walk_pte_range() | Date | Tue, 15 Apr 2008 16:00:40 +0200 |
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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> CC: Matt Mackall <mpm@selenic.com> CC: Andrew Morton <akpm@linux-foundation.org> ---
A bug is unlikely, though. kunmap_atomic() looks up the kmap entry by map-type instead of the address the pte points. So the worst thing I could find with a quick grep was that a wrong TLB entry is being flushed. Still, the code is wrong :)
diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 1cf1417..cf3c004 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -13,7 +13,7 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, private); if (err) break; - } while (pte++, addr += PAGE_SIZE, addr != end); + } while (addr += PAGE_SIZE, addr != end && pte++); pte_unmap(pte); return err;
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