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slub: fix a possible memleak in __slab_alloc()

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Zhihua Che reported a possible memleak in slub allocator on
CONFIG_PREEMPT=y builds.

It is possible current thread migrates right before disabling irqs in
__slab_alloc(). We must check again c->freelist, and perform a normal
allocation instead of scratching c->freelist.

Many thanks to Zhihua Che for spotting this bug, introduced in 2.6.39

V2: Its also possible an IRQ freed one (or several) object(s) and
populated c->freelist, so its not a CONFIG_PREEMPT only problem.

Cc: <stable@vger.kernel.org>        [2.6.39+]
Reported-by: Zhihua Che <zhihua.che@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
This commit is contained in:
Eric Dumazet 2011-12-13 04:57:06 +01:00 • committed by Pekka Enberg
parent 25f4379b8c
commit 73736e0387
1 changed files with 5 additions and 0 deletions

5
mm/slub.c
View file

@ -2169,6 +2169,11 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
goto new_slab;
}
/* must check again c->freelist in case of cpu migration or IRQ */
object = c->freelist;
if (object)
goto load_freelist;
stat(s, ALLOC_SLOWPATH);
do {