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

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Message-ID: <20180314110834.GB8564@ulmo>
Date:   Wed, 14 Mar 2018 12:08:34 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/nouveau/secboot: remove VLA usage

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>

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