[PATCH net] nfc: llcp: add missing return after LLCP_CLOSED checks

[Junxi Qian <qjx1298677004@gmail.com>]

In nfc_llcp_recv_hdlc() and nfc_llcp_recv_disc(), when the socket
state is LLCP_CLOSED, the code correctly calls release_sock() and
nfc_llcp_sock_put() but fails to return. Execution falls through to
the remainder of the function, which calls release_sock() and
nfc_llcp_sock_put() again. This results in a double release_sock()
and a refcount underflow via double nfc_llcp_sock_put(), leading to
a use-after-free.

Add the missing return statements after the LLCP_CLOSED branches
in both functions to prevent the fall-through.

Fixes: d646960f7986 ("NFC: Initial LLCP support")
Signed-off-by: Junxi Qian <qjx1298677004@gmail.com>
---
 net/nfc/llcp_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c
index 366d75663..db5bc6a87 100644
--- a/net/nfc/llcp_core.c
+++ b/net/nfc/llcp_core.c
@@ -1091,6 +1091,7 @@ static void nfc_llcp_recv_hdlc(struct nfc_llcp_local *local,
 	if (sk->sk_state == LLCP_CLOSED) {
 		release_sock(sk);
 		nfc_llcp_sock_put(llcp_sock);
+		return;
 	}
 
 	/* Pass the payload upstream */
@@ -1182,6 +1183,7 @@ static void nfc_llcp_recv_disc(struct nfc_llcp_local *local,
 	if (sk->sk_state == LLCP_CLOSED) {
 		release_sock(sk);
 		nfc_llcp_sock_put(llcp_sock);
+		return;
 	}
 
 	if (sk->sk_state == LLCP_CONNECTED) {
-- 
2.25.1