Code:  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);
 	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);
 	}
 }

Vulnerability Type: DoS 
CWE ID: 
Summary: The ping_unhash function in net/ipv4/ping.c in the Linux kernel through 4.10.8 is too late in obtaining a certain lock and consequently cannot ensure that disconnect function calls are safe, which allows local users to cause a denial of service (panic) by leveraging access to the protocol value of IPPROTO_ICMP in a socket system call.
Commit Message: ping: implement proper locking

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>