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

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Message-ID: <08ad72c3ddebb829acd66697c14e9bb5fadc6f97.camel@huaweicloud.com>
Date:   Mon, 30 Jan 2023 11:37:17 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Mimi Zohar <zohar@...ux.ibm.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 Sun, 2023-01-29 at 09:52 -0500, Mimi Zohar wrote:
> 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.

Ok, wasn't clear. I meant attestation server. The system itself is not
broken.

> "with a patch" is unnecessary.

Ok.

> > 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.

Ok, will make the changes.

Thanks

Roberto