From f9d9ef62cd3ecbd6cbb7957a253c1e81f69d5586 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 29 Sep 2011 13:11:33 +0200 Subject: [PATCH] btrfs: do not allow mounting non-subvolumes via subvol option 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 --- fs/btrfs/super.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 29eecbb6ec3a..5429b1fa0bfc 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -740,6 +740,16 @@ 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; +} + /* * This will strip out the subvol=%s argument for an argument string and add * subvolid=0 to make sure we get the actual tree root for path walking to the @@ -843,6 +853,15 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, if (error) return ERR_PTR(error); + if (!is_subvolume_inode(path.dentry->d_inode)) { + path_put(&path); + mntput(mnt); + error = -EINVAL; + printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n", + subvol_name); + return ERR_PTR(-EINVAL); + } + /* Get a ref to the sb and the dentry we found and return it */ s = path.mnt->mnt_sb; atomic_inc(&s->s_active); -- 2.30.2