linux-kernel - [PATCH 4.16 27/81] tcp: clear tp->packets

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Date:   Fri, 27 Apr 2018 15:58:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
        Sami Farin <hvtaifwkbgefbaei@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.16 27/81] tcp: clear tp->packets_out when purging write queue

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Soheil Hassas Yeganeh <soheil@...gle.com>


[ Upstream commit bffd168c3fc5cc7d2bad4c668fa90e7a9010db4b ]

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@...eaurora.org>
Reported-by: Sami Farin <hvtaifwkbgefbaei@...il.com>
Tested-by: Sami Farin <hvtaifwkbgefbaei@...il.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Acked-by: Yuchung Cheng <ycheng@...gle.com>
Acked-by: Neal Cardwell <ncardwell@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2385,6 +2385,7 @@ void tcp_write_queue_purge(struct sock *
 	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)
@@ -2434,7 +2435,6 @@ int tcp_disconnect(struct sock *sk, int
 	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;