netdev - [PATCH] ipv4: ping: Fix potential use-after-free bug

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Date:   Fri, 16 Sep 2022 18:07:27 +0800
From:   Liang He <windhl@....com>
To:     davem@...emloft.net, yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org
Cc:     windhl@....com
Subject: [PATCH] ipv4: ping: Fix potential use-after-free bug

In ping_unhash(), we should move sock_put(sk) after any possible
access point as the put function may free the object.

Fixes: c319b4d76b9e ("net: ipv4: add IPPROTO_ICMP socket kind")
Signed-off-by: Liang He <windhl@....com>
---

 I have found other places containing similar code patterns.

 net/ipv4/ping.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ping.c b/net/ipv4/ping.c
index b83c2bd9d722..f90c86d37ffc 100644
--- a/net/ipv4/ping.c
+++ b/net/ipv4/ping.c
@@ -157,10 +157,10 @@ void ping_unhash(struct sock *sk)
 	spin_lock(&ping_table.lock);
 	if (sk_hashed(sk)) {
 		hlist_nulls_del_init_rcu(&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);
+		sock_put(sk);
 	}
 	spin_unlock(&ping_table.lock);
 }
-- 
2.25.1