linux-kernel - Re: [PATCH v2] drm/nouveau/secboot: remove VLA usage

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Message-ID: <CACAvsv6NhUrskZGMJGyO42LtuNTWygsutddo_-fuhHRPCs2KWA@mail.gmail.com>
Date:   Fri, 16 Mar 2018 12:05:53 +1000
From:   Ben Skeggs <skeggsb@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        David Airlie <airlied@...ux.ie>, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        David Laight <David.Laight@...lab.com>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [PATCH v2] drm/nouveau/secboot: remove VLA usage

On 14 March 2018 at 21:08, Thierry Reding <thierry.reding@...il.com> wrote:
> On Tue, Mar 13, 2018 at 11:24:11AM -0500, Gustavo A. R. Silva wrote:
>> In preparation to enabling -Wvla, remove VLA. In this particular
>> case directly use macro NVKM_MSGQUEUE_CMDLINE_SIZE instead of local
>> variable cmdline_size. Also, remove cmdline_size as it is not
>> actually useful anymore.
>>
>> The use of stack Variable Length Arrays needs to be avoided, as they
>> can be a vector for stack exhaustion, which can be both a runtime bug
>> or a security flaw. Also, in general, as code evolves it is easy to
>> lose track of how big a VLA can get. Thus, we can end up having runtime
>> failures that are hard to debug.
>>
>> Also, fixed as part of the directive to remove all VLAs from
>> the kernel: https://lkml.org/lkml/2018/3/7/621
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>> ---
>> Changes in v2:
>>  - Use sizeof(buf) instead of NVKM_MSGQUEUE_CMDLINE_SIZE. This change
>>    is based on the feedback provided by David Laight. Thanks David.
>>
>>  drivers/gpu/drm/nouveau/nvkm/subdev/secboot/ls_ucode_msgqueue.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> Reviewed-by: Thierry Reding <treding@...dia.com>
Thanks everyone.  I've taken the patch in my tree.

Ben.

>
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