Re: [PATCH] fsverity: rework fsverity_get_digest() again

[Mimi Zohar <zohar@linux.ibm.com>]

On Mon, 2023-06-12 at 12:00 -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Address several issues with the calling convention and documentation of
> fsverity_get_digest():
> 
> - Make it provide the hash algorithm as either a FS_VERITY_HASH_ALG_*
>   value or HASH_ALGO_* value, at the caller's choice, rather than only a
>   HASH_ALGO_* value as it did before.  This allows callers to work with
>   the fsverity native algorithm numbers if they want to.  HASH_ALGO_* is
>   what IMA uses, but other users (e.g. overlayfs) should use
>   FS_VERITY_HASH_ALG_* to match fsverity-utils and the fsverity UAPI.
> 
> - Make it return the digest size so that it doesn't need to be looked up
>   separately.  Use the return value for this, since 0 works nicely for
>   the "file doesn't have fsverity enabled" case.  This also makes it
>   clear that no other errors are possible.
> 
> - Rename the 'digest' parameter to 'raw_digest' and clearly document
>   that it is only useful in combination with the algorithm ID.  This
>   hopefully clears up a point of confusion.
> 
> - Export it to modules, since overlayfs will need it for checking the
>   fsverity digests of lowerdata files
>   (https://lore.kernel.org/r/dd294a44e8f401e6b5140029d8355f88748cd8fd.1686565330.git.alexl@redhat.com).
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Acked-by: Mimi Zohar <zohar@linux.ibm.com> for the IMA piece.