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    SubjectRe: [Slub allocator] There are chances that kmem_cache_cpu->freelist gets lost if the process happens to be rescheduled to a differenet cpu before the local_irq_save() completes in __slab_alloc()
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    Le lundi 12 décembre 2011 à 09:50 -0600, Christoph Lameter a écrit :

    > Correct. Issue was introduced in 2.6.39.
    >
    > Acked-by: Christoph Lameter <cl@linux.com>
    >

    Indeed, I reproduced the leak with hackbench and lot of threads.

    Thanks

    [PATCH] 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

    Reported-by: zhihua che <zhihua.che@gmail.com>
    Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    Acked-by: Christoph Lameter <cl@linux.com>
    CC: Pekka Enberg <penberg@cs.helsinki.fi>
    CC: stable@vger.kernel.org
    ---
    mm/slub.c | 6 ++++++
    1 file changed, 6 insertions(+)

    diff --git a/mm/slub.c b/mm/slub.c
    index ed3334d..923d238 100644
    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -2166,6 +2166,12 @@ redo:
    goto new_slab;
    }

    +#ifdef CONFIG_PREEMPT
    + object = c->freelist;
    + if (object)
    + goto load_freelist;
    +#endif
    +
    stat(s, ALLOC_SLOWPATH);

    do {

    --
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