linux-kernel - Re: [PATCH v9 1/7] ima: copy only complete measurement records across kexec

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Message-ID: <fe6e3c1333a50d66dc876b5a196d3491170802a8.camel@linux.ibm.com>
Date: Wed, 05 Mar 2025 07:27:40 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Baoquan He <bhe@...hat.com>, steven chen <chenste@...ux.microsoft.com>
Cc: stefanb@...ux.ibm.com, roberto.sassu@...weicloud.com,
        roberto.sassu@...wei.com, eric.snowberg@...cle.com,
        ebiederm@...ssion.com, paul@...l-moore.com, code@...icks.com,
        bauermann@...abnow.com, linux-integrity@...r.kernel.org,
        kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, madvenka@...ux.microsoft.com,
        nramas@...ux.microsoft.com, James.Bottomley@...senpartnership.com,
        vgoyal@...hat.com, dyoung@...hat.com
Subject: Re: [PATCH v9 1/7] ima: copy only complete measurement records
 across kexec

On Wed, 2025-03-05 at 20:08 +0800, Baoquan He wrote:
> On 03/04/25 at 11:03am, steven chen wrote:
> > Carrying the IMA measurement list across kexec requires allocating a
> > buffer and copying the measurement records.  Separate allocating the
> > buffer and copying the measurement records into separate functions in
> > order to allocate the buffer at kexec 'load' and copy the measurements
> > at kexec 'execute'.
> > 
> > This patch includes the following changes:
> 
> I don't know why one patch need include so many changes. From below log,
> it should be split into separate patches. It may not need to make one
> patch to reflect one change, we should at least split and wrap several
> kind of changes to ease patch understanding and reviewing. My personal
> opinion.

Agreed, well explained.

Mimi

> 
> >  - Refactor ima_dump_measurement_list() to move the memory allocation
> >    to a separate function ima_alloc_kexec_file_buf() which allocates
> >    buffer of size 'kexec_segment_size' at kexec 'load'.
> >  - Make the local variable ima_kexec_file in ima_dump_measurement_list()
> >    a local static to the file, so that it can be accessed from 
> >    ima_alloc_kexec_file_buf(). Compare actual memory required to ensure 
> >    there is enough memory for the entire measurement record.
> >  - Copy only complete measurement records.
> >  - Make necessary changes to the function ima_add_kexec_buffer() to call
> >    the above two functions.
> >  - Compared the memory size allocated with memory size of the entire 
> >    measurement record. Copy only complete measurement records if there 
> >    is enough memory. If there is not enough memory, it will not copy
> >    any IMA measurement records, and this situation will result in a 
> >    failure of remote attestation.
> > 
> > Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
> > Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> > Signed-off-by: steven chen <chenste@...ux.microsoft.com>