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Message-ID: <51810153-eb6e-40f7-b5d0-5f72c2f4ee9b@linux.microsoft.com>
Date: Tue, 12 Mar 2024 11:14:26 -0700
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Subject: Re: [RFC PATCH v14 15/19] fsverity: consume builtin signature via LSM
 hook
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To: Eric Biggers <ebiggers@kernel.org>
Cc: corbet@lwn.net, zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com,
 tytso@mit.edu, axboe@kernel.dk, agk@redhat.com, snitzer@kernel.org,
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 linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org,
 dm-devel@lists.linux.dev, audit@vger.kernel.org,
 linux-kernel@vger.kernel.org, Deven Bowers <deven.desai@linux.microsoft.com>
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From: Fan Wu <wufan@linux.microsoft.com>
In-Reply-To: <20240312030712.GF1182@sol.localdomain>
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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