From 17c3060b1701fc69daedb4c90be6325d3d9fca8e Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Sat, 8 Apr 2017 08:07:33 -0700
Subject: [PATCH] tcp: clear saved_syn in tcp_disconnect()
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
Fixes: cd8ae85299d5 ("tcp: provide SYN headers for passive connections")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/tcp.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1e319a525d51..40ba4249a586 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2322,6 +2322,7 @@ int tcp_disconnect(struct sock *sk, int flags)
tcp_init_send_head(sk);
memset(&tp->rx_opt, 0, sizeof(tp->rx_opt));
__sk_dst_reset(sk);
+ tcp_saved_syn_free(tp);
/* Clean up fastopen related fields */
tcp_free_fastopen_req(tp);
--
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