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: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index cd426313a29819b34648086b551fe9390d8a0b0a..3b83b157b0a198d8ac043f39cf48e56cdc691103 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -535,14 +535,15 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
                if (sock_owned_by_user(sk))
                        break;
 
+               skb = tcp_rtx_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_rtx_queue_head(sk);
-               BUG_ON(!skb);
-
                tcp_mstamp_refresh(tp);
                delta_us = (u32)(tp->tcp_mstamp - skb->skb_mstamp);
                remaining = icsk->icsk_rto -