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slob: fix memory corruption

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Previously, it would be possible for prev->next to point to
&free_slob_pages, and thus we would try to move a list onto itself, and
bad things would happen.

It seems a bit hairy to be doing list operations with the list marker as
an entry, rather than a head, but...

this resolves the following crash:

  http://bugzilla.kernel.org/show_bug.cgi?id=9379

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2007-11-15 12:32:04 +01:00 committed by Linus Torvalds
parent a3474224e6
commit d32ddd8f20
1 changed files with 2 additions and 1 deletions
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3
mm/slob.c
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@ -321,7 +321,8 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node)
/* Improve fragment distribution and reduce our average
* search time by starting our next search here. (see
* Knuth vol 1, sec 2.5, pg 449) */
if (free_slob_pages.next != prev->next)
if (prev != free_slob_pages.prev &&
free_slob_pages.next != prev->next)
list_move_tail(&free_slob_pages, prev->next);
break;
}