Re: linux-4.16-rc5/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c:1723]: (warning) Possible null pointer dereference: pipe_ctx

[Andrey Grodzovsky]

The check before alone is not enough for a case where there is another 
bug introduced so that

context->stream_count is not in sync with actual number of streams 
across entire resource_context.

At least assert indeed should be there.

Andrey


On 03/12/2018 07:06 PM, Li, Roman wrote:
> There is a check just before for-loop that should ensure pipe_ctx is not null:
>
> 	/* Only supports single display */
> 	if (context->stream_count != 1)
> 		return false;
>
> To remove the subject warning - we can rather add  an assert:
> assert(pipe_ctx);
>
> Thanks,
> Roman
>
> -----Original Message-----
> From: Grodzovsky, Andrey
> Sent: Monday, March 12, 2018 6:23 PM
> To: David Binderman <dcb314@xxxxxxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>; Zhou, David(ChunMing) <David1.Zhou@xxxxxxx>; airlied@xxxxxxxx; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Wentland, Harry <Harry.Wentland@xxxxxxx>; Li, Roman <Roman.Li@xxxxxxx>
> Subject: Re: linux-4.16-rc5/drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c:1723]: (warning) Possible null pointer dereference: pipe_ctx
>
>
>
> On 03/12/2018 06:22 AM, David Binderman wrote:
> > hello there,
> >
> > Source code is
> >
> >
> >   ÂÂÂ for (i = 0; i < dc->res_pool->pipe_count; i++) {
> >   ÂÂÂÂÂÂÂ if (res_ctx->pipe_ctx[i].stream) {
> >   ÂÂÂÂÂÂÂÂÂÂÂ pipe_ctx = &res_ctx->pipe_ctx[i];
> >   ÂÂÂÂÂÂÂÂÂÂÂ *pipe_idx = i;
> >   ÂÂÂÂÂÂÂÂÂÂÂ break;
> >   ÂÂÂÂÂÂÂ }
> >   ÂÂÂ }
> Indeed something like
>
> if (!pipe_ctx)
>   ÂÂÂÂÂÂÂÂÂÂÂÂÂ return false;
>
> seems the right thing here.
>
> Harry, Roman , your opinion ?
>
> Andrey
>
> >   ÂÂÂ /* Only supports eDP */
> >   ÂÂÂ if (pipe_ctx->stream->sink->link->connector_signal !=
> > SIGNAL_TYPE_EDP)
> >   ÂÂÂÂÂÂÂ return false;
> >
> > Suggest add some code to deal with the case that the for loop doesn't
> > find what it is looking for and so pipe_ctx is NULL.
> >
> > Regards
> >
> > David Binderman
> >       
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