From d624d276d1ddacbcb12ad96832ce0c7b82cd25db Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 14 Aug 2017 17:44:43 -0700 Subject: [PATCH] tcp: fix possible deadlock in TCP stack vs BPF filter Filtering the ACK packet was not put at the right place. At this place, we already allocated a child and put it into accept queue. We absolutely need to call tcp_child_process() to release its spinlock, or we will deadlock at accept() or close() time. Found by syzkaller team (Thanks a lot !) Fixes: 8fac365f63c8 ("tcp: Add a tcp_filter hook before handle ack packet") Signed-off-by: Eric Dumazet Reported-by: Dmitry Vyukov Cc: Chenbo Feng Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 4 ++-- net/ipv6/tcp_ipv6.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index a20e7f0..e9252c7 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1722,6 +1722,8 @@ process: */ sock_hold(sk); refcounted = true; + if (tcp_filter(sk, skb)) + goto discard_and_relse; nsk = tcp_check_req(sk, skb, req, false); if (!nsk) { reqsk_put(req); @@ -1729,8 +1731,6 @@ process: } if (nsk == sk) { reqsk_put(req); - } else if (tcp_filter(sk, skb)) { - goto discard_and_relse; } else if (tcp_child_process(sk, nsk, skb)) { tcp_v4_send_reset(nsk, skb); goto discard_and_relse; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 2521690..2062101 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1456,6 +1456,8 @@ process: } sock_hold(sk); refcounted = true; + if (tcp_filter(sk, skb)) + goto discard_and_relse; nsk = tcp_check_req(sk, skb, req, false); if (!nsk) { reqsk_put(req); @@ -1464,8 +1466,6 @@ process: if (nsk == sk) { reqsk_put(req); tcp_v6_restore_cb(skb); - } else if (tcp_filter(sk, skb)) { - goto discard_and_relse; } else if (tcp_child_process(sk, nsk, skb)) { tcp_v6_send_reset(nsk, skb); goto discard_and_relse; -- 2.7.4