Messages in this thread Patch in this message | | | Date | Thu, 16 Feb 2012 16:55:24 -0800 | From | Greg KH <> | Subject | [15/15] slub: fix a possible memleak in __slab_alloc() |
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3.0-stable review patch. If anyone has any objections, please let me know.
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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@linuxfoundation.org>
--- mm/slub.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/mm/slub.c +++ b/mm/slub.c @@ -1818,6 +1818,11 @@ static void *__slab_alloc(struct kmem_ca if (unlikely(!node_match(c, node))) goto another_slab; + /* must check again c->freelist in case of cpu migration or IRQ */ + object = c->freelist; + if (object) + goto update_freelist; + stat(s, ALLOC_REFILL); load_freelist: @@ -1827,6 +1832,7 @@ load_freelist: if (kmem_cache_debug(s)) goto debug; +update_freelist: c->freelist = get_freepointer(s, object); page->inuse = page->objects; page->freelist = NULL;
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