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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
        Sami Farin <hvtaifwkbgefbaei@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        Soheil Hassas Yeganeh <soheil@google.com>,
        Yuchung Cheng <ycheng@google.com>,
        Neal Cardwell <ncardwell@google.com>
Subject: [PATCH 4.14 33/80] tcp: clear tp->packets_out when purging write queue
Date:   Fri, 27 Apr 2018 15:58:26 +0200
Message-Id: <20180427135734.655295347@linuxfoundation.org>
In-Reply-To: <20180427135732.928644313@linuxfoundation.org>
References: <20180427135732.928644313@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

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


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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/tcp.h |    1 +
 net/ipv4/tcp.c    |    1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1616,6 +1616,7 @@ static inline void tcp_write_queue_purge
 	sk_mem_reclaim(sk);
 	tcp_clear_all_retrans_hints(tcp_sk(sk));
 	tcp_init_send_head(sk);
+	tcp_sk(sk)->packets_out = 0;
 }
 
 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2354,7 +2354,6 @@ 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;