linux-hardening - Re: Coverity: nouveau_dp_irq(): Null pointer dereferences

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Date:   Fri, 11 Nov 2022 11:13:17 +0200
From:   Jani Nikula <jani.nikula@...el.com>
To:     coverity-bot <keescook@...omium.org>, Lyude Paul <lyude@...hat.com>
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org, Ilia Mirkin <imirkin@...m.mit.edu>,
        Daniel Vetter <daniel@...ll.ch>,
        Karol Herbst <kherbst@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...il.com>,
        "Nathan E. Egge" <unlord@...h.org>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        Dave Airlie <airlied@...hat.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        linux-next@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: Coverity: nouveau_dp_irq(): Null pointer dereferences

On Thu, 10 Nov 2022, coverity-bot <keescook@...omium.org> wrote:
> Hello!
>
> This is an experimental semi-automated report about issues detected by
> Coverity from a scan of next-20221110 as part of the linux-next scan project:
> https://scan.coverity.com/projects/linux-next-weekly-scan
>
> You're getting this email because you were associated with the identified
> lines of code (noted below) that were touched by commits:
>
>   Mon Aug 31 19:10:08 2020 -0400
>     a0922278f83e ("drm/nouveau/kms/nv50-: Refactor and cleanup DP HPD handling")

Hi Kees, this looks like a good idea, but maybe double check the Cc list
generation? I was Cc'd on four mails today that I thought were
irrelevant to me.

Thanks,
Jani.

>
> Coverity reported the following:
>
> *** CID 1527266:  Null pointer dereferences  (REVERSE_INULL)
> drivers/gpu/drm/nouveau/nouveau_dp.c:237 in nouveau_dp_irq()
> 231     	struct nouveau_encoder *outp = find_encoder(connector, DCB_OUTPUT_DP);
> 232     	struct nouveau_drm *drm = nouveau_drm(outp->base.base.dev);
> 233     	struct nv50_mstm *mstm;
> 234     	u64 hpd = 0;
> 235     	int ret;
> 236
> vvv     CID 1527266:  Null pointer dereferences  (REVERSE_INULL)
> vvv     Null-checking "outp" suggests that it may be null, but it has already been dereferenced on all paths leading to the check.
> 237     	if (!outp)
> 238     		return;
> 239
> 240     	mstm = outp->dp.mstm;
> 241     	NV_DEBUG(drm, "service %s\n", connector->name);
> 242
>
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):
>
> Reported-by: coverity-bot <keescook+coverity-bot@...omium.org>
> Addresses-Coverity-ID: 1527266 ("Null pointer dereferences")
> Fixes: a0922278f83e ("drm/nouveau/kms/nv50-: Refactor and cleanup DP HPD handling")
>
> Thanks for your attention!

-- 
Jani Nikula, Intel Open Source Graphics Center