linux-kernel - Re: [PATCH v3 2/2] ima: Introduce MMAP_CHECK

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Date:   Sun, 29 Jan 2023 09:52:51 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, stefanb@...ux.ibm.com,
        viro@...iv.linux.org.uk, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v3 2/2] ima: Introduce MMAP_CHECK_REQPROT hook

On Thu, 2023-01-26 at 17:38 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@...wei.com>
> 
> Commit 98de59bfe4b2f ("take calculation of final prot in
> security_mmap_file() into a helper") caused ima_file_mmap() to receive the
> protections requested by the application and not those applied by the
> kernel.
> 
> After restoring the original MMAP_CHECK behavior with a patch, existing
> systems might be broken due to not being ready to handle new entries
> (previously missing) in the IMA measurement list.

Is this a broken system or a broken attestation server?  The
attestation server might not be able to handle the additional
measurements, but the system, itself, is not broken.

"with a patch" is unnecessary.

> 
> Restore the original correct MMAP_CHECK behavior instead of keeping the

^ add missing comma after "behavior"

> current buggy one and introducing a new hook with the correct behavior. The
> second option 

^ The second option -> Otherwise,

> would have had the risk of IMA users not noticing the problem
> at all, as they would actively have to update the IMA policy, to switch to
> the correct behavior.
> 
> Also, introduce the new MMAP_CHECK_REQPROT hook to keep the current
> behavior, so that IMA users could easily fix a broken system, although this
> approach is discouraged due to potentially missing measurements.

Again, is this a broken system or a broken attestation server? 

> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>

Otherwise, the patch looks good.

-- 
thanks,

Mimi