tcp: tcp_v4_err() should be more careful

[ Upstream commit 2c4cc9712364c051b1de2d175d5fbea6be948ebf ]

ICMP handlers are not very often stressed, we should
make them more resilient to bugs that might surface in
the future.

If there is no packet in retransmit queue, we should
avoid a NULL deref.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: soukjin bae <soukjin.bae@samsung.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ee8399f11fd088dbff829784ffb3c17d816573b1..b3d6b8e77300dfc504ceb605159d80eb9c5c44db 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -466,14 +466,15 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                if (sock_owned_by_user(sk))
                        break;
 
+               skb = tcp_write_queue_head(sk);
+               if (WARN_ON_ONCE(!skb))
+                       break;
+
                icsk->icsk_backoff--;
                icsk->icsk_rto = tp->srtt_us ? __tcp_set_rto(tp) :
                                               TCP_TIMEOUT_INIT;
                icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
 
-               skb = tcp_write_queue_head(sk);
-               BUG_ON(!skb);
-
                remaining = icsk->icsk_rto -
                            min(icsk->icsk_rto,
                                tcp_time_stamp - tcp_skb_timestamp(skb));