netdev - [PATCH] net-tcp: fix panic in tcp_fastopen_cache

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Date:	Wed, 13 Nov 2013 15:00:46 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Dave Jones <davej@...hat.com>, David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH] net-tcp: fix panic in tcp_fastopen_cache_set()

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

We had some reports of crashes using TCP fastopen, and Dave Jones
gave a nice stack trace pointing to the error.

Issue is that tcp_get_metrics() should not be called with a NULL dst

Fixes: 1fe4c481ba637 ("net-tcp: Fast Open client - cookie cache")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Dave Jones <davej@...hat.com>
Cc: Yuchung Cheng <ycheng@...gle.com>
---
 net/ipv4/tcp_metrics.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 2ab09cbae74d..d3ee2e0c28b6 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -663,10 +663,13 @@ void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
 			    struct tcp_fastopen_cookie *cookie, bool syn_lost)
 {
+	struct dst_entry *dst = __sk_dst_get(sk);
 	struct tcp_metrics_block *tm;
 
+	if (!dst)
+		return;
 	rcu_read_lock();
-	tm = tcp_get_metrics(sk, __sk_dst_get(sk), true);
+	tm = tcp_get_metrics(sk, dst, true);
 	if (tm) {
 		struct tcp_fastopen_metrics *tfom = &tm->tcpm_fastopen;
 


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