af_packet: avoid erroring out after sock_init_data() in packet_create()

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>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 2ff4b251842d496a99d05ef3c4a9179ffef96237..886c0dd47b66210e4bbaf8e78f1778c2d25b896e 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3422,17 +3422,17 @@ 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;
@@ -3464,7 +3464,7 @@ 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;