bt_sock_alloc() allocates the sk object and attaches it to the provided
sock object. On error l2cap_sock_alloc() frees the sk object, but the
dangling pointer is still attached to the sock object, which may create
use-after-free in other code.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
---
 net/bluetooth/l2cap_sock.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index ba437c6f6ee5..18e89e764f3b 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1886,6 +1886,7 @@ static struct sock *l2cap_sock_alloc(struct net *net, struct socket *sock,
 	chan = l2cap_chan_create();
 	if (!chan) {
 		sk_free(sk);
+		sock->sk = NULL;
 		return NULL;
 	}
 
-- 
2.39.5

From: Ignat Korchagin <ignat@cloudflare.com>
Date: Mon, 14 Oct 2024 16:38:01 +0100
> bt_sock_alloc() allocates the sk object and attaches it to the provided
> sock object. On error l2cap_sock_alloc() frees the sk object, but the
> dangling pointer is still attached to the sock object, which may create
> use-after-free in other code.
> 
> Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Checked all bt_sock_alloc() paths and confirmed only rfcomm and l2cap
need changes.

On Mon, Oct 14, 2024 at 11:23 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>
> From: Ignat Korchagin <ignat@cloudflare.com>
> Date: Mon, 14 Oct 2024 16:38:01 +0100
> > bt_sock_alloc() allocates the sk object and attaches it to the provided
> > sock object. On error l2cap_sock_alloc() frees the sk object, but the
> > dangling pointer is still attached to the sock object, which may create
> > use-after-free in other code.
> >
> > Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
>
> Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
>
> Checked all bt_sock_alloc() paths and confirmed only rfcomm and l2cap
> need changes.

Reviewed-by: Eric Dumazet <edumazet@google.com>