[PATCH AUTOSEL 5.10 10/33] af_packet: avoid erroring out after sock_init_data() in packet_create()

[Sasha Levin <sashal@kernel.org>]

From: Ignat Korchagin <ignat@cloudflare.com>

[ Upstream commit 46f2a11cb82b657fd15bab1c47821b635e03838b ]

After sock_init_data() the allocated sk object is attached to the provided
sock object. On error, packet_create() frees the sk object leaving the
dangling pointer in the sock object on return. Some other code may try
to use this pointer and cause use-after-free.

Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241014153808.51894-2-ignat@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/packet/af_packet.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index ce3e20bcde4ab..01a191c8194b4 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3386,18 +3386,18 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
 	if (sock->type == SOCK_PACKET)
 		sock->ops = &packet_ops_spkt;
 
+	po = pkt_sk(sk);
+	err = packet_alloc_pending(po);
+	if (err)
+		goto out_sk_free;
+
 	sock_init_data(sock, sk);
 
-	po = pkt_sk(sk);
 	init_completion(&po->skb_completion);
 	sk->sk_family = PF_PACKET;
 	po->num = proto;
 	po->xmit = dev_queue_xmit;
 
-	err = packet_alloc_pending(po);
-	if (err)
-		goto out2;
-
 	packet_cached_dev_reset(po);
 
 	sk->sk_destruct = packet_sock_destruct;
@@ -3432,7 +3432,7 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
 	preempt_enable();
 
 	return 0;
-out2:
+out_sk_free:
 	sk_free(sk);
 out:
 	return err;
-- 
2.43.0