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Subject[patch] slob: fix memory corruption

* Ingo Molnar <mingo@elte.hu> wrote:

> > I had implemented SLOB in userspace, so I resynched and think I
> > found your problem. Sorry for the attachment format -- this mailer
> > isn't the best. I'm really computer illiterate when it comes to
> > userspace...
>
> thx, i'll try your fix in a minute.

that did the trick! Nick, find an updated patch below. (reference to the
bugzilla added.)

Ingo

-------------------->
Subject: slob: fix memory corruption
From: Nick Piggin <npiggin@suse.de>

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>
---
mm/slob.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux/mm/slob.c
===================================================================
--- linux.orig/mm/slob.c
+++ linux/mm/slob.c
@@ -321,7 +321,8 @@ static void *slob_alloc(size_t size, gfp
/* 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;
}
-
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