[SRU][N][PATCH 1/1] net: inet6: do not leave a dangling sk pointer in inet6_create()

[Massimiliano Pellizzer]

From: Ignat Korchagin <ignat at cloudflare.com>

CVE-2024-56600

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 at cloudflare.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu at amazon.com>
Reviewed-by: Eric Dumazet <edumazet at google.com>
Link: https://patch.msgid.link/20241014153808.51894-8-ignat@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
(cherry picked from commit 9df99c395d0f55fb444ef39f4d6f194ca437d884)
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 net/ipv6/af_inet6.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 959bfd9f6344..5374c5f9b764 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -251,31 +251,29 @@ 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,
-- 
2.43.0