ecryptfs: extend ro check to private mount

So far ecryptfs only verified that the superblock wasn't read-only but
didn't check whether the mount was. This made sense when we did not use
a private mount because the read-only state could change at any point.

Now that we have a private mount and mount properties can't change
behind our back extend the read-only check to include the vfsmount.

The __mnt_is_readonly() helper will check both the mount and the
superblock.  Note that before we checked root->d_sb and now we check
mnt->mnt_sb but since we have a matching <vfsmount, dentry> pair here
this is only syntactical change, not a semantic one.

Overlayfs and cachefiles have been changed to check this as well.

Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Tyler Hicks <code@tyhicks.com>
Cc: ecryptfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
1 file changed