From f0295c3fe30d58888c555314e803e352903894b5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 14 Feb 2017 09:03:51 -0800 Subject: [PATCH] packet: fix races in fanout_add() 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. [js] no rollover in 3.12 Fixes: dc99f600698d ("packet: Add fanout support.") Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby Signed-off-by: Willy Tarreau [sw0312.kim: cherry-pick from linux-3.10.y to fix CVE-2017-6346] Signed-off-by: Seung-Woo Kim Change-Id: Ia81bda1ccaf66462fea305c918353b0d34f63e71 --- net/packet/af_packet.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 8220608..642b2c8 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1318,13 +1318,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) 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 && @@ -1380,17 +1383,16 @@ static void fanout_release(struct sock *sk) struct packet_sock *po = pkt_sk(sk); struct packet_fanout *f; - f = po->fanout; - if (!f) - return; - mutex_lock(&fanout_mutex); - po->fanout = NULL; + f = po->fanout; + if (f) { + po->fanout = NULL; - 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); } -- 2.7.4