[PATCH] drm/i915: Allow NULL memory region

[Dan Carpenter]

On Wed, Jul 17, 2024 at 05:05:55PM +0200, Nirmoy Das wrote:
> 
> On 7/12/2024 11:41 PM, Jonathan Cavitt wrote:
> > Prevent a NULL pointer access in intel_memory_regions_hw_probe.
> > 
> > Fixes: 05da7d9f717b ("drm/i915/gem: Downgrade stolen lmem setup warning")
> > Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
> > Signed-off-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
> > ---
> >   drivers/gpu/drm/i915/intel_memory_region.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_memory_region.c b/drivers/gpu/drm/i915/intel_memory_region.c
> > index 172dfa7c3588b..d40ee1b42110a 100644
> > --- a/drivers/gpu/drm/i915/intel_memory_region.c
> > +++ b/drivers/gpu/drm/i915/intel_memory_region.c
> > @@ -368,8 +368,10 @@ int intel_memory_regions_hw_probe(struct drm_i915_private *i915)
> >   			goto out_cleanup;
> >   		}
> > -		mem->id = i;
> > -		i915->mm.regions[i] = mem;
> 
> There is a check for mem just before that. You could use IS_ERR_OR_NULL(mem)
> instead of IS_ERR().

An error pointer return is normally completely different from a NULL
return in how it's handled.  Here NULL is a special kind of success.  I
wrote a blog about this.

https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/

regards,
dan carpenter