Patch "tcp: clear saved_syn in tcp_disconnect()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

tcp: clear saved_syn in tcp_disconnect()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-clear-saved_syn-in-tcp_disconnect.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Sat, 8 Apr 2017 08:07:33 -0700
Subject: tcp: clear saved_syn in tcp_disconnect()

From: Eric Dumazet <[email protected]>

[ Upstream commit 17c3060b1701fc69daedb4c90be6325d3d9fca8e ]

In the (very unlikely) case a passive socket becomes a listener, we do not want to duplicate its saved SYN headers.

This would lead to double frees, use after free, and please hackers and various fuzzers

Tested:

    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3

+0 setsockopt(3, IPPROTO_TCP, TCP_SAVE_SYN, [1], 4) = 0 +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0

+0 bind(3, ..., ...) = 0
+0 listen(3, 5) = 0

+0 < S 0:0(0) win 32972 <mss 1460,nop,wscale 7> +0 > S. 0:0(0) ack 1 <...>
+.1 < . 1:1(0) ack 1 win 257
+0 accept(3, ..., ...) = 4

+0 connect(4, AF_UNSPEC, ...) = 0
+0 close(3) = 0
+0 bind(4, ..., ...) = 0
+0 listen(4, 5) = 0

+0 < S 0:0(0) win 32972 <mss 1460,nop,wscale 7> +0 > S. 0:0(0) ack 1 <...>
+.1 < . 1:1(0) ack 1 win 257

---
 net/ipv4/tcp.c |    1 +
 1 file changed, 1 insertion(+)

@@ -2260,6 +2260,7 @@ int tcp_disconnect(struct sock *sk, int
 	tcp_init_send_head(sk);
 	memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
 	__sk_dst_reset(sk);
+	tcp_saved_syn_free(tp);
 
 	WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/tcp-clear-saved_syn-in-tcp_disconnect.patch queue-4.4/net-packet-fix-overflow-in-check-for-tp_frame_nr.patch queue-4.4/net-packet-fix-overflow-in-check-for-tp_reserve.patch queue-4.4/net-neigh-guard-against-null-solicit-method.patch