linux-kernel - Re: [Nouveau] [PATCH] drm/nouveau: remove redundant null check on array mstm->msto

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Message-ID: <CACvgo53Bg=HkA-ohgrybg=FqS-p-oxehhsnrA_ZpQpGPo7Oy7Q@mail.gmail.com>
Date:   Thu, 17 Aug 2017 13:21:17 +0100
From:   Emil Velikov <emil.l.velikov@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        ML nouveau <nouveau@...ts.freedesktop.org>,
        kernel-janitors@...r.kernel.org,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: Re: [Nouveau] [PATCH] drm/nouveau: remove redundant null check on
 array mstm->msto

On 17 August 2017 at 11:37, Colin King <colin.king@...onical.com> wrote:
> From: Colin Ian King <colin.king@...onical.com>
>
> The check to see if mstm->msto is null is redundant because it is
> an array and hence can never be null.  Remove the redundant check.
>
> Detected by CoverityScan, CID#1375915 ("Array compared against 0")
>
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/nouveau/nv50_display.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nv50_display.c b/drivers/gpu/drm/nouveau/nv50_display.c
> index f7b4326a4641..51e9081b95a0 100644
> --- a/drivers/gpu/drm/nouveau/nv50_display.c
> +++ b/drivers/gpu/drm/nouveau/nv50_display.c
> @@ -3141,7 +3141,7 @@ nv50_mstc_new(struct nv50_mstm *mstm, struct drm_dp_mst_port *port,
>         mstc->connector.funcs->reset(&mstc->connector);
>         nouveau_conn_attach_properties(&mstc->connector);
>
> -       for (i = 0; i < ARRAY_SIZE(mstm->msto) && mstm->msto; i++)
> +       for (i = 0; i < ARRAY_SIZE(mstm->msto); i++)
I think that should be mstm->msto[i]. After all we are dereferencing
the pointer, so we don't want to crash.

>                 drm_mode_connector_attach_encoder(&mstc->connector, &mstm->msto[i]->encoder);

-Emil