[PATCH] drm/i915: Allow NULL memory region

[Nirmoy Das]

On 7/17/2024 5:25 PM, Dan Carpenter wrote:
> 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.


intel_memory_regions_driver_release() skipped my eyes  in the cleanup path.

>   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/


I am the perfect target audience for this blog post :)


Thanks,

Nirmoy

>
> regards,
> dan carpenter