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 <[e-mail]>
Cc: [e-mail]
Signed-off-by: Steve French <[e-mail]>

fs/cifs/connect.c

···
 		 */
 	}
 
-	kfree(server->hostname);
 	kfree(server);
 
 	length = atomic_dec_return(&tcpSesAllocCount);
···
 	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;
···
 	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)
···
 		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;
···
 
 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

···
 	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);
···
 	pos = strpbrk(devname + 2, delims);
 	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;
···
 	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

···
 	char *password;
 	char *domainname;
 	char *source;
+	char *server_hostname;
 	char *UNC;
 	char *nodename;
 	char *iocharset;  /* local code page for mapping to and from Unicode */