Subject: [PATCH v2 7/8] net: inet: do not leave a dangling sk pointer in inet_create()

From: Ignat Korchagin <[email-masked]>
Date: Mon, 7 Oct 2024 22:35:01 +0100

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

Clear the sk pointer in the sock object on error.

Signed-off-by: Ignat Korchagin <[email-masked]>
---
 net/ipv4/af_inet.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index b24d74616637..8095e82de808 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -376,32 +376,30 @@ static int inet_create(struct net *net, struct socket *sock, int protocol,
 		inet->inet_sport = htons(inet->inet_num);
 		/* Add to protocol hash chains. */
 		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;
 }

-- 
2.39.5