3.2.87-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet <edumazet@xxxxxxxxxx> commit d199fab63c11998a602205f7ee7ff7c05c97164b upstream. Multiple threads can call fanout_add() at the same time. We need to grab fanout_mutex earlier to avoid races that could lead to one thread freeing po->rollover that was set by another thread. Do the same in fanout_release(), for peace of mind, and to help us finding lockdep issues earlier. Fixes: dc99f600698d ("packet: Add fanout support.") Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Cc: Willem de Bruijn <willemb@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> [bwh: Backported to 3.2: - No rollover queue stats - Adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1286,13 +1286,16 @@ static int fanout_add(struct sock *sk, u return -EINVAL; } + mutex_lock(&fanout_mutex); + + err = -EINVAL; if (!po->running) - return -EINVAL; + goto out; + err = -EALREADY; if (po->fanout) - return -EALREADY; + goto out; - mutex_lock(&fanout_mutex); match = NULL; list_for_each_entry(f, &fanout_list, list) { if (f->id == id && @@ -1348,17 +1351,16 @@ static void fanout_release(struct sock * struct packet_sock *po = pkt_sk(sk); struct packet_fanout *f; + mutex_lock(&fanout_mutex); f = po->fanout; - if (!f) - return; - - po->fanout = NULL; + if (f) { + po->fanout = NULL; - mutex_lock(&fanout_mutex); - if (atomic_dec_and_test(&f->sk_ref)) { - list_del(&f->list); - dev_remove_pack(&f->prot_hook); - kfree(f); + if (atomic_dec_and_test(&f->sk_ref)) { + list_del(&f->list); + dev_remove_pack(&f->prot_hook); + kfree(f); + } } mutex_unlock(&fanout_mutex); }