Commit 73736e03 authored Dec 13, 2011 by Eric Dumazet Committed by Pekka Enberg Dec 13, 2011

slub: fix a possible memleak in __slab_alloc()



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>

parent 25f4379b

mm/slub.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -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 {