Nouveau - Nov 2022 - Coverity: nouveau_dp_irq(): Null pointer dereferences

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")

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 at chromium.org>
Addresses-Coverity-ID: 1527266 ("Null pointer dereferences")
Fixes: a0922278f83e ("drm/nouveau/kms/nv50-: Refactor and cleanup DP HPD
handling")

Thanks for your attention!

-- 
Coverity-bot

On Thu, 10 Nov 2022, coverity-bot <keescook at chromium.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 at chromium.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