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    Subject[patch 12/22] slub: Fix kmem_cache_destroy() with SLAB_DESTROY_BY_RCU
    2.6.30-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    From: Eric Dumazet <eric.dumazet@gmail.com>

    commit d76b1590e06a63a3d8697168cd0aabf1c4b3cb3a upstream.

    kmem_cache_destroy() should call rcu_barrier() *after* kmem_cache_close() and
    *before* sysfs_slab_remove() or risk rcu_free_slab() being called after
    kmem_cache is deleted (kfreed).

    rmmod nf_conntrack can crash the machine because it has to kmem_cache_destroy()
    a SLAB_DESTROY_BY_RCU enabled cache.

    Reported-by: Zdenek Kabelac <zdenek.kabelac@gmail.com>
    Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
    Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    mm/slub.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/mm/slub.c
    +++ b/mm/slub.c
    @@ -2490,8 +2490,6 @@ static inline int kmem_cache_close(struc
    */
    void kmem_cache_destroy(struct kmem_cache *s)
    {
    - if (s->flags & SLAB_DESTROY_BY_RCU)
    - rcu_barrier();
    down_write(&slub_lock);
    s->refcount--;
    if (!s->refcount) {
    @@ -2502,6 +2500,8 @@ void kmem_cache_destroy(struct kmem_cach
    "still has objects.\n", s->name, __func__);
    dump_stack();
    }
    + if (s->flags & SLAB_DESTROY_BY_RCU)
    + rcu_barrier();
    sysfs_slab_remove(s);
    } else
    up_write(&slub_lock);



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