slob: fix memory corruption
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>
diff --git a/mm/slob.c b/mm/slob.c
index 5bc2ceb..08a9bd9 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -321,7 +321,8 @@
/* 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;
}