• Eric Dumazet's avatar
    netfilter: nf_conntrack: nf_conntrack_alloc() fixes · 941297f4
    Eric Dumazet authored
    When a slab cache uses SLAB_DESTROY_BY_RCU, we must be careful when allocating
    objects, since slab allocator could give a freed object still used by lockless
    In particular, nf_conntrack RCU lookups rely on ct->tuplehash[xxx].hnnode.next
    being always valid (ie containing a valid 'nulls' value, or a valid pointer to next
    object in hash chain.)
    kmem_cache_zalloc() setups object with NULL values, but a NULL value is not valid
    for ct->tuplehash[xxx].hnnode.next.
    Fix is to call kmem_cache_alloc() and do the zeroing ourself.
    As spotted by Patrick, we also need to make sure lookup keys are committed to
    memory before setting refcount to 1, or a lockless reader could get a reference
    on the old version of the object. Its key re-check could then pass the barrier.
    Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
    Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
rculist_nulls.txt 5.1 KB