[PATCH net] nfc: llcp: check socket state after locking in nfc_llcp_recv_dm()

[Aldo Ariel Panzardo <qwe.aldo@gmail.com>]

Between nfc_llcp_connecting_sock_get() and lock_sock(), another
thread can move the socket from connecting_sockets to sockets via
a failed connect + re-bind. After lock_sock(), the socket may no
longer be in LLCP_CONNECTING state, so unconditionally unlinking
from connecting_sockets corrupts the wrong list.

Add a state check after acquiring the socket lock: only unlink
from connecting_sockets if the socket is still LLCP_CONNECTING.

Fixes: bf1460acdf8c ("nfc: llcp: Fix list corruption / refcount desync in nfc_llcp_recv_dm()")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
---
 net/nfc/llcp_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index 74bf81700..acf113311 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -1326,7 +1326,7 @@ static void nfc_llcp_recv_dm(struct nfc_llcp_local *local,
 	 * corrupt the connecting_sockets list / desync the socket refcount.
 	 * This mirrors nfc_llcp_recv_cc().
 	 */
-	if (connecting)
+	if (connecting && sk->sk_state == LLCP_CONNECTING)
 		nfc_llcp_sock_unlink(&local->connecting_sockets, sk);
 
 	sk->sk_err = ENXIO;
-- 
2.43.0