netdev - [PATCH net-next] tcp: fix tcp_send_syn

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Message-ID: <1508361630.31614.142.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 18 Oct 2017 14:20:30 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>, Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] tcp: fix tcp_send_syn_data()

From: Eric Dumazet <edumazet@...gle.com>

syn_data was allocated by sk_stream_alloc_skb(), meaning
its destructor and _skb_refdst fields are mangled.

We need to call tcp_skb_tsorted_anchor_cleanup() before
calling kfree_skb() or kernel crashes.

Bug was reported by syzkaller bot.

Fixes: e2080072ed2d ("tcp: new list for sent but unacked skbs for RACK recovery")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
---
 net/ipv4/tcp_output.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 53dc1267c85e668d9a6d5d60d24e6101f7a9c56b..988733f289c8c43f3ed88a9ae1b7f272ab8de1a2 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3383,6 +3383,7 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
 		int copied = copy_from_iter(skb_put(syn_data, space), space,
 					    &fo->data->msg_iter);
 		if (unlikely(!copied)) {
+			tcp_skb_tsorted_anchor_cleanup(syn_data);
 			kfree_skb(syn_data);
 			goto fallback;
 		}