netdev - [PATCH net-next] tcp/dccp: fix potential NULL deref in __inet_inherit

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Message-ID: <1444827518.4166.27.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 14 Oct 2015 05:58:38 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] tcp/dccp: fix potential NULL deref in
 __inet_inherit_port()

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

As we no longer hold listener lock in fast path, it is possible that a
child is created right after listener freed its bound port, if a close()
is done while incoming packets are processed.

__inet_inherit_port() must detect this and return an error,
so that caller can free the child earlier.

Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/inet_hashtables.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 08643a3616af..958728a22001 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -137,6 +137,10 @@ int __inet_inherit_port(const struct sock *sk, struct sock *child)
 
 	spin_lock(&head->lock);
 	tb = inet_csk(sk)->icsk_bind_hash;
+	if (unlikely(!tb)) {
+		spin_unlock(&head->lock);
+		return -ENOENT;
+	}
 	if (tb->port != port) {
 		/* NOTE: using tproxy and redirecting skbs to a proxy
 		 * on a different listener port breaks the assumption


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