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

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Message-ID: <5fc967a5-5627-6308-f42b-786be477c30b@canonical.com>
Date:   Thu, 17 Aug 2017 14:02:07 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Emil Velikov <emil.l.velikov@...il.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 17/08/17 13:21, Emil Velikov wrote:
> 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.

Yes, that makes far more sense. I'll send a V2. Thanks Emil.

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