Commit bb289b7b authored by Omar Sandoval's avatar Omar Sandoval Committed by Chris Mason
Browse files

Btrfs: fail on mismatched subvol and subvolid mount options 



There's nothing to stop a user from passing both subvol= and subvolid=
to mount, but if they don't refer to the same subvolume, someone is
going to be surprised at some point. Error out on this case, but allow
users to pass in both if they do match (which they could, for example,
get out of /proc/mounts).

Reviewed-by: default avatarDavid Sterba <dsterba@suse.cz>
Signed-off-by: default avatarOmar Sandoval <osandov@osandov.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent fa330659

fs/btrfs/super.c

+25 −8
Original line number Diff line number Diff line
@@ -1167,8 +1167,9 @@ static char *setup_root_args(char *args) 
	return buf;

}



static struct dentry *mount_subvol(const char *subvol_name, int flags,

				   const char *device_name, char *data)

static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,

				   int flags, const char *device_name,

				   char *data)

{

	struct dentry *root;

	struct vfsmount *mnt = NULL;
@@ -1214,12 +1215,27 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, 
	/* mount_subtree() drops our reference on the vfsmount. */

	mnt = NULL;



	if (!IS_ERR(root) && !is_subvolume_inode(d_inode(root))) {

	if (!IS_ERR(root)) {

		struct super_block *s = root->d_sb;

		struct inode *root_inode = d_inode(root);

		u64 root_objectid = BTRFS_I(root_inode)->root->root_key.objectid;



		ret = 0;

		if (!is_subvolume_inode(root_inode)) {

			pr_err("BTRFS: '%s' is not a valid subvolume\n",

			       subvol_name);

			ret = -EINVAL;

		}

		if (subvol_objectid && root_objectid != subvol_objectid) {

			pr_err("BTRFS: subvol '%s' does not match subvolid %llu\n",

			       subvol_name, subvol_objectid);

			ret = -EINVAL;

		}

		if (ret) {

			dput(root);

		root = ERR_PTR(-EINVAL);

			root = ERR_PTR(ret);

			deactivate_locked_super(s);

		pr_err("BTRFS: '%s' is not a valid subvolume\n", subvol_name);

		}

	}



out:
@@ -1312,7 +1328,8 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, 


	if (subvol_name) {

		/* mount_subvol() will free subvol_name. */

		return mount_subvol(subvol_name, flags, device_name, data);

		return mount_subvol(subvol_name, subvol_objectid, flags,

				    device_name, data);

	}



	security_init_mnt_opts(&new_sec_opts);

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