linux-kernel - Re: [PATCH v7 1/7] ima: define and call ima_alloc_kexec_file

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Message-ID: <4d258641d36088b1a1239724a2951211159d81f0.camel@linux.ibm.com>
Date: Thu, 06 Feb 2025 11:49:48 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: steven chen <chenste@...ux.microsoft.com>, 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
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
        James.Bottomley@...senPartnership.com
Subject: Re: [PATCH v7 1/7] ima: define and call ima_alloc_kexec_file_buf

Thanks, Steven, for picking up and working on Tushar's patch set.

I normally finish reviewing the patch set, before commenting.  In this case, there's
a generic comment that relates to all of the patches.  It's also a way of letting you
know that I've started reviewing the patch set.  The remaining comments will come
after I finish reviewing the patch set.

On Mon, 2025-02-03 at 15:20 -0800, 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:
>  - 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 as many measurement events as possible.
>  - 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. If there is not enough memory, it will copy as many
>    IMA measurement records as possible, and this situation will result
>    in a failure of remote attestation.
> 
> Author: Tushar Sugandhi <tusharsu@...ux.microsoft.com>

I understand you want to credit Tushar for the patch, but the mechanism is described
in Documentation/process/submitting-patches.rst.  Refer to the paragraph on "Co-
developed-by".  There is no tag named "Author".

> Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>

"Suggested-by" goes before the Signed-off-by tag(s). "Reviewed-by" tag goes after
your and/or Tushar's Signed-off-tag.

> Signed-off-by: Tushar Sugandhi <tusharsu@...ux.microsoft.com>
> Signed-off-by: steven chen <chenste@...ux.microsoft.com>

Before the "Co-developed-by" tag was defined, it was implied simply by this ordering
of the "Signed-off-by" tags.

For those patches you didn't modify, simply import Tushar's patch with him as the
author and add your Signed-off-by tag after his.

thanks,

Mimi