IMA: use vfs_getattr_nosec to get the i_version

IMA: use vfs_getattr_nosec to get the i_version

IMA currently accesses the i_version out of the inode directly when it
does a measurement. This is fine for most simple filesystems, but can be
problematic with more complex setups (e.g. overlayfs).

Make IMA instead call vfs_getattr_nosec to get this info. This allows
the filesystem to determine whether and how to report the i_version, and
should allow IMA to work properly with a broader class of filesystems in
the future.

Reported-and-Tested-by: Stefan Berger <[email protected]>
Reviewed-by: Christian Brauner <[email protected]>
Signed-off-by: Jeff Layton <[email protected]>
Signed-off-by: Mimi Zohar <[email protected]>