cifs: To match file servers, make sure the server hostname matches

We generally rely on a bunch of factors to differentiate between servers.
For example, IP address, port etc.

For certain server types (like Azure), it is important to make sure
that the server hostname matches too, even if the both hostnames currently
resolve to the same IP address.
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/connect.c

@@ -794,7 +794,6 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 		 */
 	}
 
-	kfree(server->hostname);
 	kfree(server);
 
 	length = atomic_dec_return(&tcpSesAllocCount);
@@ -1235,6 +1234,9 @@ static int match_server(struct TCP_Server_Info *server, struct smb3_fs_context *
 	if (!net_eq(cifs_net_ns(server), current->nsproxy->net_ns))
 		return 0;
 
+	if (strcasecmp(server->hostname, ctx->server_hostname))
+		return 0;
+
 	if (!match_address(server, addr,
 			   (struct sockaddr *)&ctx->srcaddr))
 		return 0;
@@ -1336,6 +1338,7 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect)
 	kfree(server->session_key.response);
 	server->session_key.response = NULL;
 	server->session_key.len = 0;
+	kfree(server->hostname);
 
 	task = xchg(&server->tsk, NULL);
 	if (task)
@@ -1361,14 +1364,15 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 		goto out_err;
 	}
 
+	tcp_ses->hostname = kstrdup(ctx->server_hostname, GFP_KERNEL);
+	if (!tcp_ses->hostname) {
+		rc = -ENOMEM;
+		goto out_err;
+	}
+
 	tcp_ses->ops = ctx->ops;
 	tcp_ses->vals = ctx->vals;
 	cifs_set_net_ns(tcp_ses, get_net(current->nsproxy->net_ns));
-	tcp_ses->hostname = extract_hostname(ctx->UNC);
-	if (IS_ERR(tcp_ses->hostname)) {
-		rc = PTR_ERR(tcp_ses->hostname);
-		goto out_err_crypto_release;
-	}
 
 	tcp_ses->conn_id = atomic_inc_return(&tcpSesNextId);
 	tcp_ses->noblockcnt = ctx->rootfs;
@@ -1497,8 +1501,7 @@ cifs_get_tcp_session(struct smb3_fs_context *ctx)
 
 out_err:
 	if (tcp_ses) {
-		if (!IS_ERR(tcp_ses->hostname))
-			kfree(tcp_ses->hostname);
+		kfree(tcp_ses->hostname);
 		if (tcp_ses->ssocket)
 			sock_release(tcp_ses->ssocket);
 		kfree(tcp_ses);

fs/cifs/fs_context.c

@@ -318,6 +318,7 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
 	DUP_CTX_STR(mount_options);
 	DUP_CTX_STR(username);
 	DUP_CTX_STR(password);
+	DUP_CTX_STR(server_hostname);
 	DUP_CTX_STR(UNC);
 	DUP_CTX_STR(source);
 	DUP_CTX_STR(domainname);
@@ -456,6 +457,11 @@ smb3_parse_devname(const char *devname, struct smb3_fs_context *ctx)
 	if (!pos)
 		return -EINVAL;
 
+	/* record the server hostname */
+	ctx->server_hostname = kstrndup(devname + 2, pos - devname - 2, GFP_KERNEL);
+	if (!ctx->server_hostname)
+		return -ENOMEM;
+
 	/* skip past delimiter */
 	++pos;
 
@@ -1496,6 +1502,8 @@ smb3_cleanup_fs_context_contents(struct smb3_fs_context *ctx)
 	ctx->username = NULL;
 	kfree_sensitive(ctx->password);
 	ctx->password = NULL;
+	kfree(ctx->server_hostname);
+	ctx->server_hostname = NULL;
 	kfree(ctx->UNC);
 	ctx->UNC = NULL;
 	kfree(ctx->source);

fs/cifs/fs_context.h

@@ -166,6 +166,7 @@ struct smb3_fs_context {
 	char *password;
 	char *domainname;
 	char *source;
+	char *server_hostname;
 	char *UNC;
 	char *nodename;
 	char *iocharset;  /* local code page for mapping to and from Unicode */