NFC: Add sockaddr length checks before accessing sa_family in bind handlers

Verify that the caller-provided sockaddr structure is large enough to
contain the sa_family field, before accessing it in bind() handlers of the
AF_NFC socket. Since the syscall doesn't enforce a minimum size of the
corresponding memory region, very short sockaddrs (zero or one byte long)
result in operating on uninitialized memory while referencing .sa_family.

Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

net/nfc/llcp_sock.c

@@ -77,7 +77,8 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen)
 	struct sockaddr_nfc_llcp llcp_addr;
 	int len, ret = 0;
 
-	if (!addr || addr->sa_family != AF_NFC)
+	if (!addr || alen < offsetofend(struct sockaddr, sa_family) ||
+	    addr->sa_family != AF_NFC)
 		return -EINVAL;
 
 	pr_debug("sk %p addr %p family %d\n", sk, addr, addr->sa_family);
@@ -151,7 +152,8 @@ static int llcp_raw_sock_bind(struct socket *sock, struct sockaddr *addr,
 	struct sockaddr_nfc_llcp llcp_addr;
 	int len, ret = 0;
 
-	if (!addr || addr->sa_family != AF_NFC)
+	if (!addr || alen < offsetofend(struct sockaddr, sa_family) ||
+	    addr->sa_family != AF_NFC)
 		return -EINVAL;
 
 	pr_debug("sk %p addr %p family %d\n", sk, addr, addr->sa_family);