Bluetooth: RFCOMM: avoid leaving dangling sk pointer in rfcomm_sock_alloc()

bt_sock_alloc() attaches allocated sk object to the provided sock object.
If rfcomm_dlc_alloc() fails, we release the sk object, but leave the
dangling pointer in the sock object, which may cause use-after-free.

Fix this by swapping calls to bt_sock_alloc() and rfcomm_dlc_alloc().

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/20241014153808.51894-4-ignat@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c
index f48250e3f2e103c75d5937e1608e43c123aa3297..355e1a1698f56ca6fd6d3b1da708c836e01e1932 100644 (file)
--- a/net/bluetooth/rfcomm/sock.c
+++ b/net/bluetooth/rfcomm/sock.c
@@ -274,13 +274,13 @@ static struct sock *rfcomm_sock_alloc(struct net *net, struct socket *sock,
        struct rfcomm_dlc *d;
        struct sock *sk;
 
-       sk = bt_sock_alloc(net, sock, &rfcomm_proto, proto, prio, kern);
-       if (!sk)
+       d = rfcomm_dlc_alloc(prio);
+       if (!d)
                return NULL;
 
-       d = rfcomm_dlc_alloc(prio);
-       if (!d) {
-               sk_free(sk);
+       sk = bt_sock_alloc(net, sock, &rfcomm_proto, proto, prio, kern);
+       if (!sk) {
+               rfcomm_dlc_free(d);
                return NULL;
        }