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>

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 */
 };