tcp: clear tp->packets_out when purging write queue

Clear tp->packets_out when purging the write queue, otherwise
tcp_rearm_rto() mistakenly assumes TCP write queue is not empty.
This results in NULL pointer dereference.

Also, remove the redundant `tp->packets_out = 0` from
tcp_disconnect(), since tcp_disconnect() calls
tcp_write_queue_purge().

Fixes: a27fd7a8ed38 (tcp: purge write queue upon RST)
Reported-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Reported-by: Sami Farin <hvtaifwkbgefbaei@gmail.com>
Tested-by: Sami Farin <hvtaifwkbgefbaei@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4fa3f81..9ce1c72 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2368,6 +2368,7 @@ void tcp_write_queue_purge(struct sock *sk)
        INIT_LIST_HEAD(&tcp_sk(sk)->tsorted_sent_queue);
        sk_mem_reclaim(sk);
        tcp_clear_all_retrans_hints(tcp_sk(sk));
+       tcp_sk(sk)->packets_out = 0;
 }
 
 int tcp_disconnect(struct sock *sk, int flags)
@@ -2417,7 +2418,6 @@ int tcp_disconnect(struct sock *sk, int flags)
        icsk->icsk_backoff = 0;
        tp->snd_cwnd = 2;
        icsk->icsk_probes_out = 0;
-       tp->packets_out = 0;
        tp->snd_ssthresh = TCP_INFINITE_SSTHRESH;
        tp->snd_cwnd_cnt = 0;
        tp->window_clamp = 0;