Bluetooth: L2CAP: do not leave dangling sk pointer on error in l2cap_sock_create()

Bluetooth: L2CAP: do not leave dangling sk pointer on error in l2cap_sock_create()

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>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241014153808.51894-3-ignat@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>