Doug / smarc-fsl-linux-kernel

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Commit f9d9ef62cd3ecbd6cbb7957a253c1e81f69d5586

Authored by David Sterba
1 parent 20bcd64934
Exists in master and in 6 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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 <dsterba@suse.cz>

Showing 1 changed file with 19 additions and 0 deletions Side-by-side Diff

... ... @@ -741,6 +741,16 @@
741 741 }
742 742  
743 743 /*
  744 + * subvolumes are identified by ino 256
  745 + */
  746 +static inline int is_subvolume_inode(struct inode *inode)
  747 +{
  748 + if (inode && inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
  749 + return 1;
  750 + return 0;
  751 +}
  752 +
  753 +/*
744 754 * This will strip out the subvol=%s argument for an argument string and add
745 755 * subvolid=0 to make sure we get the actual tree root for path walking to the
746 756 * subvol we want.
... ... @@ -842,6 +852,15 @@
842 852 put_mnt_ns(ns_private);
843 853 if (error)
844 854 return ERR_PTR(error);
  855 +
  856 + if (!is_subvolume_inode(path.dentry->d_inode)) {
  857 + path_put(&path);
  858 + mntput(mnt);
  859 + error = -EINVAL;
  860 + printk(KERN_ERR "btrfs: '%s' is not a valid subvolume\n",
  861 + subvol_name);
  862 + return ERR_PTR(-EINVAL);
  863 + }
845 864  
846 865 /* Get a ref to the sb and the dentry we found and return it */
847 866 s = path.mnt->mnt_sb;