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Subject[PATCH 4.16 27/81] tcp: clear tp->packets_out when purging write queue
Date
4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Soheil Hassas Yeganeh <soheil@google.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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;

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