From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Sterba Subject: [PATCH] btrfs: do not allow mounting non-subvolumes via subvol option Date: Fri, 29 Jul 2011 12:14:08 +0200 Message-ID: <1311934448-887-1-git-send-email-dsterba@suse.cz> Cc: chris.mason@oracle.com, David Sterba To: linux-btrfs@vger.kernel.org Return-path: List-ID: There's a missing test whether the path passed to subvol=path option during mount is a real subvolume, allowing any directory located in default subovlume to be passed and accepted for mount. (current btrfs progs prevent this early) $ btrfs subvol snapshot . p1-snap ERROR: '.' is not a subvolume (with "is subvolume?" test bypassed) $ btrfs subvol snapshot . p1-snap Create a snapshot of '.' in './p1-snap' $ btrfs subvol list -p . ID 258 parent 5 top level 5 path subvol ID 259 parent 5 top level 5 path subvol1 ID 260 parent 5 top level 5 path default-subvol1 ID 262 parent 5 top level 5 path p1/p1-snapshot ID 263 parent 259 top level 5 path subvol1/subvol1-snap The problem I see is that this makes a false impression of snapshotting the given subvolume but in fact snapshots the default one: a user expects outcome like ID 263 but in fact gets ID 262 . This patch makes mount fail with EINVAL with a message in syslog. Signed-off-by: David Sterba --- I did not find a better errno than EINVAL, probably adding someting like ENSUBVOL would be better so that other filesystems with such functionality may use it in future. fs/btrfs/super.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 15634d4..0c2a1d1 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -753,6 +753,15 @@ static int btrfs_set_super(struct super_block *s, void *data) return set_anon_super(s, data); } +/* + * subvolumes are identified by ino 256 + */ +static inline int is_subvolume_inode(struct inode *inode) +{ + if (inode && inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) + return 1; + return 0; +} /* * Find a superblock for the given device / mount point. @@ -873,6 +882,16 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, error = -ENXIO; goto error_free_subvol_name; } + + if (!is_subvolume_inode(new_root->d_inode)) { + dput(root); + dput(new_root); + deactivate_locked_super(s); + error = -EINVAL; + printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n", + subvol_name); + goto error_free_subvol_name; + } dput(root); root = new_root; } else { -- 1.7.6