[PATCH 1/2] cifs: To match file servers, make sure the server hostname matches

[Tim Gardner]

From: Shyam Prasad N <sprasad at microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/1950336

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 at microsoft.com>
Cc: stable at vger.kernel.org
Signed-off-by: Steve French <stfrench at microsoft.com>
(cherry picked from commit 7be3248f313930ff3d3436d4e9ddbe9fccc1f541)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 fs/cifs/connect.c    | 19 +++++++++++--------
 fs/cifs/fs_context.c |  8 ++++++++
 fs/cifs/fs_context.h |  1 +
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 3912040b89ad..3635724c13dd 100644
--- a/fs/cifs/connect.c
+++ b/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);
diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index 727c8835b222..05aa0a238e99 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -332,6 +332,7 @@ 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);
@@ -470,6 +471,11 @@ 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;
 
@@ -1510,6 +1516,8 @@ 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);
diff --git a/fs/cifs/fs_context.h b/fs/cifs/fs_context.h
index b6243972edf3..ac4b631d8ce3 100644
--- a/fs/cifs/fs_context.h
+++ b/fs/cifs/fs_context.h
@@ -169,6 +169,7 @@ 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 */
-- 
2.33.1