[PATCH net-next v3 1/9] af_packet: avoid erroring out after sock_init_data() in packet_create()

From: Ignat Korchagin
Date: Mon Oct 14 2024 - 11:39:06 EST


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@xxxxxxxxxx>
Signed-off-by: Ignat Korchagin <ignat@xxxxxxxxxxxxxx>
---
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 f8942062f776..99ae27d1e4dc 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3421,17 +3421,17 @@ 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;

- err = packet_alloc_pending(po);
- if (err)
- goto out2;
-
packet_cached_dev_reset(po);

sk->sk_destruct = packet_sock_destruct;
@@ -3463,7 +3463,7 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
sock_prot_inuse_add(net, &packet_proto, 1);

return 0;
-out2:
+out_sk_free:
sk_free(sk);
out:
return err;
--
2.39.5