[PATCH 3/3] 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/1954926

commit 7be3248f313930ff3d3436d4e9ddbe9fccc1f541 upstream.

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>
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
[rtg - backported by the Microsoft team. They dropped changes to
fs/cifs/fs_connect.[ch], added a structure tag to fs/cifs/cifsglob.h: struct smb_vol,
misc changes to fs/cifs/connect.c to reflect the intent of the original upstream patch]
---
 fs/cifs/cifsglob.h |  1 +
 fs/cifs/connect.c  | 38 ++++++++++++++++++++++++++++++--------
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 10934d4d5ce33..9607f623c1357 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -538,6 +538,7 @@ struct smb_vol {
 	char *username;
 	char *password;
 	char *domainname;
+	char *server_hostname;
 	char *UNC;
 	char *iocharset;  /* local code page for mapping to and from Unicode */
 	char source_rfc1001_name[RFC1001_NAME_LEN_WITH_NULL]; /* clnt nb name */
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index de188a8b282a5..dfcac2489b46b 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1101,7 +1101,6 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 		 */
 	}
 
-	kfree(server->hostname);
 	kfree(server);
 
 	length = atomic_dec_return(&tcpSesAllocCount);
@@ -1653,6 +1652,11 @@ cifs_parse_devname(const char *devname, struct smb_vol *vol)
 	if (!pos)
 		return -EINVAL;
 
+	/* record the server hostname */
+	vol->server_hostname = kstrndup(devname + 2, pos - devname - 2, GFP_KERNEL);
+	if (!vol->server_hostname)
+		return -ENOMEM;
+
 	/* skip past delimiter */
 	++pos;
 
@@ -2510,6 +2514,12 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 		goto cifs_parse_mount_err;
 	}
 #endif
+
+	if (!vol->server_hostname) {
+		cifs_dbg(VFS, "CIFS mount error: Unable to parse server name in device string!\n");
+		goto cifs_parse_mount_err;
+	}
+
 	if (!vol->UNC) {
 		cifs_dbg(VFS, "CIFS mount error: No usable UNC path provided in device string!\n");
 		goto cifs_parse_mount_err;
@@ -2712,6 +2722,9 @@ static int match_server(struct TCP_Server_Info *server, struct smb_vol *vol)
 	if (!net_eq(cifs_net_ns(server), current->nsproxy->net_ns))
 		return 0;
 
+	if (strcasecmp(server->hostname, vol->server_hostname))
+		return 0;
+
 	if (!match_address(server, addr,
 			   (struct sockaddr *)&vol->srcaddr))
 		return 0;
@@ -2796,6 +2809,7 @@ 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)
@@ -2821,14 +2835,15 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 		goto out_err;
 	}
 
+	tcp_ses->hostname = kstrdup(volume_info->server_hostname, GFP_KERNEL);
+	if (!tcp_ses->hostname) {
+		rc = -ENOMEM;
+		goto out_err;
+	}
+
 	tcp_ses->ops = volume_info->ops;
 	tcp_ses->vals = volume_info->vals;
 	cifs_set_net_ns(tcp_ses, get_net(current->nsproxy->net_ns));
-	tcp_ses->hostname = extract_hostname(volume_info->UNC);
-	if (IS_ERR(tcp_ses->hostname)) {
-		rc = PTR_ERR(tcp_ses->hostname);
-		goto out_err_crypto_release;
-	}
 
 	tcp_ses->noblockcnt = volume_info->rootfs;
 	tcp_ses->noblocksnd = volume_info->noblocksnd || volume_info->rootfs;
@@ -2942,8 +2957,7 @@ cifs_get_tcp_session(struct smb_vol *volume_info)
 
 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);
@@ -4272,6 +4286,7 @@ cifs_cleanup_volume_info_contents(struct smb_vol *volume_info)
 	kfree(volume_info->username);
 	kzfree(volume_info->password);
 	kfree(volume_info->UNC);
+	kfree(volume_info->server_hostname);
 	kfree(volume_info->domainname);
 	kfree(volume_info->iocharset);
 	kfree(volume_info->prepath);
@@ -4541,6 +4556,12 @@ static int update_vol_info(const struct dfs_cache_tgt_iterator *tgt_it,
 	kfree(vol->UNC);
 	vol->UNC = new_unc;
 
+	if (fake_vol->server_hostname) {
+		kfree(vol->server_hostname);
+		vol->server_hostname = fake_vol->server_hostname;
+		fake_vol->server_hostname = NULL;
+	}
+
 	if (fake_vol->prepath) {
 		kfree(vol->prepath);
 		vol->prepath = fake_vol->prepath;
@@ -5342,6 +5363,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	vol_info->linux_uid = fsuid;
 	vol_info->cred_uid = fsuid;
 	vol_info->UNC = master_tcon->treeName;
+	vol_info->server_hostname = master_tcon->ses->server->hostname;
 	vol_info->retry = master_tcon->retry;
 	vol_info->nocase = master_tcon->nocase;
 	vol_info->nohandlecache = master_tcon->nohandlecache;
-- 
2.34.1