Commit d0242061 authored Jan 15, 2014 by David Sterba Committed by Chris Mason Jan 28, 2014

btrfs: restrict snapshotting to own subvolumes

Currently, any user can snapshot any subvolume if the path is accessible and
thus indirectly create and keep files he does not own under his direcotries.
This is not possible with traditional directories.

In security context, a user can snapshot root filesystem and pin any
potentially buggy binaries, even if the updates are applied.

All the snapshots are visible to the administrator, so it's possible to
verify if there are suspicious snapshots.

Another more practical problem is that any user can pin the space used
by eg. root and cause ENOSPC.

Original report:
https://bugs.launchpad.net/ubuntu/+source/apparmor/+bug/484786



CC: stable@vger.kernel.org
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent 89d4346a

fs/btrfs/ioctl.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -1574,6 +1574,12 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
		btrfs_info(BTRFS_I(src_inode)->root->fs_info,
		"Snapshot src from another FS");
		ret = -EINVAL;
		} else if (!inode_owner_or_capable(src_inode)) {
		/*
		* Subvolume creation is not restricted, but snapshots
		* are limited to own subvolumes only
		*/
		ret = -EPERM;
		} else {
		ret = btrfs_mksubvol(&file->f_path, name, namelen,
		BTRFS_I(src_inode)->root,

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