ping: implement proper locking

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@google.com>
Reported-by: Daniel Jiang <danieljiang0415@gmail.com>
Reported-by: Solar Designer <solar@openwall.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index 105c0748c52f..e612991c9185 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -156,17 +156,18 @@ int ping_hash(struct sock *sk)
 void ping_unhash(struct sock *sk)
 {
         struct inet_sock *isk = inet_sk(sk);
+
         pr_debug("ping_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 = 0;
                 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);
 }
 EXPORT_SYMBOL_GPL(ping_unhash);