cifs: fix potential memory leaks in session setup

Make sure to free cifs_ses::auth_key.response before allocating it as
we might end up leaking memory in reconnect or mounting.
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsencrypt.c

@@ -278,6 +278,7 @@ build_avpair_blob(struct cifs_ses *ses, const struct nls_table *nls_cp)
 	 * ( for NTLMSSP_AV_NB_DOMAIN_NAME followed by NTLMSSP_AV_EOL ) +
 	 * unicode length of a netbios domain name
 	 */
+	kfree_sensitive(ses->auth_key.response);
 	ses->auth_key.len = size + 2 * dlen;
 	ses->auth_key.response = kzalloc(ses->auth_key.len, GFP_KERNEL);
 	if (!ses->auth_key.response) {

fs/cifs/sess.c

@@ -815,6 +815,7 @@ int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
 		return -EINVAL;
 	}
 	if (tilen) {
+		kfree_sensitive(ses->auth_key.response);
 		ses->auth_key.response = kmemdup(bcc_ptr + tioffset, tilen,
 						 GFP_KERNEL);
 		if (!ses->auth_key.response) {
@@ -1428,6 +1429,7 @@ sess_auth_kerberos(struct sess_data *sess_data)
 		goto out_put_spnego_key;
 	}
 
+	kfree_sensitive(ses->auth_key.response);
 	ses->auth_key.response = kmemdup(msg->data, msg->sesskey_len,
 					 GFP_KERNEL);
 	if (!ses->auth_key.response) {

fs/cifs/smb2pdu.c

@@ -1453,6 +1453,7 @@ SMB2_auth_kerberos(struct SMB2_sess_data *sess_data)
 
 	/* keep session key if binding */
 	if (!is_binding) {
+		kfree_sensitive(ses->auth_key.response);
 		ses->auth_key.response = kmemdup(msg->data, msg->sesskey_len,
 						 GFP_KERNEL);
 		if (!ses->auth_key.response) {