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Subject[042/129] slub: fix a possible memleak in __slab_alloc()
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
Content-Length: 1140
Lines: 41
From: Eric Dumazet <eric.dumazet@gmail.com>

commit 73736e0387ba0e6d2b703407b4d26168d31516a7 upstream.

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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
mm/slub.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2166,6 +2166,11 @@ redo:
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 {



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