smb3: do not allow insecure cifs mounts when using smb3

if mounting as smb3 do not allow cifs (vers=1.0) or insecure vers=2.0
mounts.

For example:
root@smf-Thinkpad-P51:~/cifs-2.6# mount -t smb3 //127.0.0.1/scratch /mnt -o username=testuser,password=Testpass1
root@smf-Thinkpad-P51:~/cifs-2.6# umount /mnt
root@smf-Thinkpad-P51:~/cifs-2.6# mount -t smb3 //127.0.0.1/scratch /mnt -o username=testuser,password=Testpass1,vers=1.0
mount: /mnt: wrong fs type, bad option, bad superblock on //127.0.0.1/scratch ...
root@smf-Thinkpad-P51:~/cifs-2.6# dmesg | grep smb3
[ 4302.200122] CIFS VFS: vers=1.0 (cifs) not permitted when mounting with smb3
root@smf-Thinkpad-P51:~/cifs-2.6# mount -t smb3 //127.0.0.1/scratch /mnt -o username=testuser,password=Testpass1,vers=3.11

Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Sachin Prabhu <sprabhu@redhat.com>

3 files changed, 36 insertions, 14 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index eb7b6573f322..d5aa7ae917bf 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -698,8 +698,8 @@ static int cifs_set_super(struct super_block *sb, void *data)
 }
 
 static struct dentry *
-cifs_do_mount(struct file_system_type *fs_type,
-	      int flags, const char *dev_name, void *data)
+cifs_smb3_do_mount(struct file_system_type *fs_type,
+	      int flags, const char *dev_name, void *data, bool is_smb3)
 {
 	int rc;
 	struct super_block *sb;
@@ -710,7 +710,7 @@ cifs_do_mount(struct file_system_type *fs_type,
 
 	cifs_dbg(FYI, "Devname: %s flags: %d\n", dev_name, flags);
 
-	volume_info = cifs_get_volume_info((char *)data, dev_name);
+	volume_info = cifs_get_volume_info((char *)data, dev_name, is_smb3);
 	if (IS_ERR(volume_info))
 		return ERR_CAST(volume_info);
 
@@ -790,6 +790,20 @@ out_nls:
 	goto out;
 }
 
+static struct dentry *
+smb3_do_mount(struct file_system_type *fs_type,
+	      int flags, const char *dev_name, void *data)
+{
+	return cifs_smb3_do_mount(fs_type, flags, dev_name, data, true);
+}
+
+static struct dentry *
+cifs_do_mount(struct file_system_type *fs_type,
+	      int flags, const char *dev_name, void *data)
+{
+	return cifs_smb3_do_mount(fs_type, flags, dev_name, data, false);
+}
+
 static ssize_t
 cifs_loose_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
@@ -925,7 +939,7 @@ MODULE_ALIAS_FS("cifs");
 static struct file_system_type smb3_fs_type = {
 	.owner = THIS_MODULE,
 	.name = "smb3",
-	.mount = cifs_do_mount,
+	.mount = smb3_do_mount,
 	.kill_sb = cifs_kill_sb,
 	/*  .fs_flags */
 };
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 84765c8764bf..4e0d183c3d10 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -211,7 +211,7 @@ extern int cifs_setup_cifs_sb(struct smb_vol *pvolume_info,
 extern int cifs_match_super(struct super_block *, void *);
 extern void cifs_cleanup_volume_info(struct smb_vol *pvolume_info);
 extern struct smb_vol *cifs_get_volume_info(char *mount_data,
-					    const char *devname);
+					    const char *devname, bool is_smb3);
 extern int cifs_mount(struct cifs_sb_info *, struct smb_vol *);
 extern void cifs_umount(struct cifs_sb_info *);
 extern void cifs_mark_open_files_invalid(struct cifs_tcon *tcon);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 9089b73809de..96645a7d8f27 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -320,7 +320,7 @@ static int generic_ip_connect(struct TCP_Server_Info *server);
 static void tlink_rb_insert(struct rb_root *root, struct tcon_link *new_tlink);
 static void cifs_prune_tlinks(struct work_struct *work);
 static int cifs_setup_volume_info(struct smb_vol *volume_info, char *mount_data,
-					const char *devname);
+					const char *devname, bool is_smb3);
 
 /*
  * cifs tcp session reconnection
@@ -1166,7 +1166,7 @@ cifs_parse_cache_flavor(char *value, struct smb_vol *vol)
 }
 
 static int
-cifs_parse_smb_version(char *value, struct smb_vol *vol)
+cifs_parse_smb_version(char *value, struct smb_vol *vol, bool is_smb3)
 {
 	substring_t args[MAX_OPT_ARGS];
 
@@ -1176,6 +1176,10 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol)
 			cifs_dbg(VFS, "mount with legacy dialect disabled\n");
 			return 1;
 		}
+		if (is_smb3) {
+			cifs_dbg(VFS, "vers=1.0 (cifs) not permitted when mounting with smb3\n");
+			return 1;
+		}
 		vol->ops = &smb1_operations;
 		vol->vals = &smb1_values;
 		break;
@@ -1184,6 +1188,10 @@ cifs_parse_smb_version(char *value, struct smb_vol *vol)
 			cifs_dbg(VFS, "mount with legacy dialect disabled\n");
 			return 1;
 		}
+		if (is_smb3) {
+			cifs_dbg(VFS, "vers=2.0 not permitted when mounting with smb3\n");
+			return 1;
+		}
 		vol->ops = &smb20_operations;
 		vol->vals = &smb20_values;
 		break;
@@ -1272,7 +1280,7 @@ cifs_parse_devname(const char *devname, struct smb_vol *vol)
 
 static int
 cifs_parse_mount_options(const char *mountdata, const char *devname,
-			 struct smb_vol *vol)
+			 struct smb_vol *vol, bool is_smb3)
 {
 	char *data, *end;
 	char *mountdata_copy = NULL, *options;
@@ -1985,7 +1993,7 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			if (string == NULL)
 				goto out_nomem;
 
-			if (cifs_parse_smb_version(string, vol) != 0)
+			if (cifs_parse_smb_version(string, vol, is_smb3) != 0)
 				goto cifs_parse_mount_err;
 			got_version = true;
 			break;
@@ -3797,7 +3805,7 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
 		} else {
 			cleanup_volume_info_contents(volume_info);
 			rc = cifs_setup_volume_info(volume_info, mdata,
-							fake_devname);
+							fake_devname, false);
 		}
 		kfree(fake_devname);
 		kfree(cifs_sb->mountdata);
@@ -3810,11 +3818,11 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
 
 static int
 cifs_setup_volume_info(struct smb_vol *volume_info, char *mount_data,
-			const char *devname)
+			const char *devname, bool is_smb3)
 {
 	int rc = 0;
 
-	if (cifs_parse_mount_options(mount_data, devname, volume_info))
+	if (cifs_parse_mount_options(mount_data, devname, volume_info, is_smb3))
 		return -EINVAL;
 
 	if (volume_info->nullauth) {
@@ -3848,7 +3856,7 @@ cifs_setup_volume_info(struct smb_vol *volume_info, char *mount_data,
 }
 
 struct smb_vol *
-cifs_get_volume_info(char *mount_data, const char *devname)
+cifs_get_volume_info(char *mount_data, const char *devname, bool is_smb3)
 {
 	int rc;
 	struct smb_vol *volume_info;
@@ -3857,7 +3865,7 @@ cifs_get_volume_info(char *mount_data, const char *devname)
 	if (!volume_info)
 		return ERR_PTR(-ENOMEM);
 
-	rc = cifs_setup_volume_info(volume_info, mount_data, devname);
+	rc = cifs_setup_volume_info(volume_info, mount_data, devname, is_smb3);
 	if (rc) {
 		cifs_cleanup_volume_info(volume_info);
 		volume_info = ERR_PTR(rc);