ima: detect changes to the backing overlay file

Commit 18b44bc5a672 ("ovl: Always reevaluate the file signature for
IMA") forced signature re-evaulation on every file access.

Instead of always re-evaluating the file's integrity, detect a change
to the backing file, by comparing the cached file metadata with the
backing file's metadata.  Verifying just the i_version has not changed
is insufficient.  In addition save and compare the i_ino and s_dev
as well.

Reviewed-by: Amir Goldstein <[email protected]>
Tested-by: Eric Snowberg <[email protected]>
Tested-by: Raul E Rangel <[email protected]>
Cc: [email protected]
Signed-off-by: Mimi Zohar <[email protected]>

0 files changed, 0 insertions, 0 deletions