linux-kernel - [PATCH 3.2 073/101] ping: implement proper locking

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Message-ID: <lsq.1496331655.480348712@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:40:55 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
        "Andrey Konovalov" <andreyknvl@...gle.com>,
        "Solar Designer" <solar@...nwall.com>,
        "Daniel Jiang" <danieljiang0415@...il.com>,
        "Eric Dumazet" <edumazet@...gle.com>
Subject: [PATCH 3.2 073/101] ping: implement proper locking

3.2.89-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 43a6684519ab0a6c52024b5e25322476cabad893 upstream.

We got a report of yet another bug in ping

http://www.openwall.com/lists/oss-security/2017/03/24/6

->disconnect() is not called with socket lock held.

Fix this by acquiring ping rwlock earlier.

Thanks to Daniel, Alexander and Andrey for letting us know this problem.

Fixes: c319b4d76b9e ("net: ipv4: add IPPROTO_ICMP socket kind")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Daniel Jiang <danieljiang0415@...il.com>
Reported-by: Solar Designer <solar@...nwall.com>
Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/ipv4/ping.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -135,16 +135,17 @@ static void ping_v4_hash(struct sock *sk
 static void ping_v4_unhash(struct sock *sk)
 {
 	struct inet_sock *isk = inet_sk(sk);
+
 	pr_debug("ping_v4_unhash(isk=%p,isk->num=%u)\n", isk, isk->inet_num);
+	write_lock_bh(&ping_table.lock);
 	if (sk_hashed(sk)) {
-		write_lock_bh(&ping_table.lock);
 		hlist_nulls_del(&sk->sk_nulls_node);
 		sk_nulls_node_init(&sk->sk_nulls_node);
 		sock_put(sk);
 		isk->inet_num = isk->inet_sport = 0;
 		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
-		write_unlock_bh(&ping_table.lock);
 	}
+	write_unlock_bh(&ping_table.lock);
 }
 
 static struct sock *ping_v4_lookup(struct net *net, u32 saddr, u32 daddr,