net: inet6: do not leave a dangling sk pointer in inet6_create()

JIRA: https://issues.redhat.com/browse/RHEL-72313
CVE: CVE-2024-56600

commit 9df99c3
Author: Ignat Korchagin <ignat@cloudflare.com>
Date:   Mon Oct 14 16:38:06 2024 +0100

    net: inet6: do not leave a dangling sk pointer in inet6_create()

    sock_init_data() attaches the allocated sk pointer to the provided sock
    object. If inet6_create() fails later, the sk object is released, but the
    sock object retains the dangling sk pointer, which may cause use-after-free
    later.

    Clear the sock sk pointer on error.

    Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
    Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Reviewed-by: Eric Dumazet <edumazet@google.com>
    Link: https://patch.msgid.link/20241014153808.51894-8-ignat@cloudflare.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

Author: CKI Backport Bot

net/ipv6/af_inet6.c

@@ -260,31 +260,29 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
 		 */
 		inet->inet_sport = htons(inet->inet_num);
 		err = sk->sk_prot->hash(sk);
-		if (err) {
-			sk_common_release(sk);
-			goto out;
-		}
+		if (err)
+			goto out_sk_release;
 	}
 	if (sk->sk_prot->init) {
 		err = sk->sk_prot->init(sk);
-		if (err) {
-			sk_common_release(sk);
-			goto out;
-		}
+		if (err)
+			goto out_sk_release;
 	}
 
 	if (!kern) {
 		err = BPF_CGROUP_RUN_PROG_INET_SOCK(sk);
-		if (err) {
-			sk_common_release(sk);
-			goto out;
-		}
+		if (err)
+			goto out_sk_release;
 	}
 out:
 	return err;
 out_rcu_unlock:
 	rcu_read_unlock();
 	goto out;
+out_sk_release:
+	sk_common_release(sk);
+	sock->sk = NULL;
+	goto out;
 }
 
 static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,