linux-kernel - Re: [PATCH v4 0/5] kexec_file: Add buffer hand-over for the next kernel

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Date:   Wed, 07 Sep 2016 09:19:40 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc:     kexec@...ts.infradead.org, linux-security-module@...r.kernel.org,
        linux-ima-devel@...ts.sourceforge.net,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Dave Young <dyoung@...hat.com>,
        Vivek Goyal <vgoyal@...hat.com>, Baoquan He <bhe@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Stewart Smith <stewart@...ux.vnet.ibm.com>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        Eric Richter <erichte@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Balbir Singh <bsingharora@...il.com>
Subject: Re: [PATCH v4 0/5] kexec_file: Add buffer hand-over for the next kernel

ebiederm@...ssion.com (Eric W. Biederman) writes:

> Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com> writes:
>
>> Hello,
>>
>> The purpose of this new version of the series is to fix a small issue that
>> I found, which is that the kernel doesn't remove the memory reservation
>> for the hand-over buffer it received from the previous kernel in the
>> device tree it sets up for the next kernel. The result is that for each
>> successive kexec, a stale hand-over buffer is left behind, wasting memory.
>>
>> This is fixed by changes to kexec_free_handover_buffer and
>> setup_handover_buffer in patch 2. The other change is to fix checkpatch
>> warnings in the last patch.
>
> This is fundamentally broken.  You do not increase the integrity of a
> system by dropping integrity checks.
>
> No. No. No. No.
>
> Nacked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

To be constructive the way we have handled similiar situations in the
past (hotplu memory) is to call kexec_load again.

Eric