Re: [RFC PATCH v14 15/19] fsverity: consume builtin signature via LSM hook

[Fan Wu <wufan@linux.microsoft.com>]

On 3/11/2024 8:07 PM, Eric Biggers wrote:
> On Mon, Mar 11, 2024 at 07:57:12PM -0700, Eric Biggers wrote:
>>
>> As I've said before, this commit message needs some work.  It currently doesn't
>> say anything about what the patch actually does.
>>
>> BTW, please make sure you're Cc'ing the fsverity mailing list
>> (fsverity@lists.linux.dev), not fscrypt (linux-fscrypt@vger.kernel.org).
> 
> Also, I thought this patch was using a new LSM hook, but I now see that you're
> actually abusing the existing security_inode_setsecurity() LSM hook.  Currently
> that hook is called when an xattr is set.  I don't see any precedent for
> overloading it for other purposes.  This seems problematic, as it means that a
> request to set an xattr with the name you chose ("fsverity.builtin-sig") will be
> interpreted by LSMs as the fsverity builtin signature.  A dedicated LSM hook may
> be necessary to avoid issues with overloading the existing xattr hook like this.
> 
> - Eric

Thanks for the suggestion. I found that using 
security_inode_setsecurity() causes issues with SMACK's 
inode_setsecurity() hook. I will crate a dedicated new hook like 
security_inode_setsig() in the next version.

-Fan