[PATCH AUTOSEL 4.19 05/21] af_packet: avoid erroring out after sock_init_data() in packet_create()

Sasha Levin
2024-11-24T13:57:21Z

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 b285a6e1a7669..31b2a843611be 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3346,18 +3346,18 @@ 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;
@@ -3392,7 +3392,7 @@ 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