Re: [PATCH 2/2] drm/amd/display: Fix null pointer dereference in error message

[Cong Liu]

> On 2023-09-26 01:56, Cong Liu wrote:
> > This patch fixes a null pointer dereference in the error message that is
> > printed when the Display Core (DC) fails to initialize. The original
> > message includes the DC version number, which is undefined if the DC is
> > not initialized.
> >
> > Fixes: 9788d087caff ("drm/amd/display: improve the message printed when loading DC")
> > Signed-off-by: Cong Liu <liucong2@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 8e98dda1e084..bf52a909f558 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -1703,8 +1703,7 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
> >   		DRM_INFO("Display Core v%s initialized on %s\n", DC_VER,
> >   			 dce_version_to_string(adev->dm.dc->ctx->dce_version));
> >   	} else {
> > -		DRM_INFO("Display Core v%s failed to initialize on %s\n", DC_VER,
> > -			 dce_version_to_string(adev->dm.dc->ctx->dce_version));
> > +		DRM_INFO("Display Core failed to initialize with v%s!\n", DC_VER);
>
> There is value in printing the version number. Let's not remove it.
>
> Instead you can probably fix it by doing a NULL check on adev->dm.dc->ctx.

Hi Harry

I don't understand what you mean. Are you saying that I need to add a 
NULL check in the if statement (i.e. if(adev->dm.dc && 
adev->dm.dc->ctx)), because adev->dm.dc is NULL in the else statement 
and there is no way to print adev->dm.dc->ctx->dce_version.

Regards
Cong

> Harry
>
> >   		goto error;
> >   	}
> >