[PATCH] drm/amdgpu: fix a possible null pointer dereference

[Joshua Ashton]

Maybe that wasn't you or whatever, but your last patch that did this got 
some CVE assigned to it that didn't really make any sense, given this is 
just a null deref that'd end up as an oops?

It can only happen if the kzalloc in drm_mode_create fails.

I imagine that the `continue` is not the best cause of action anyway, 
it's probably not worth adding some broken connector with a bunch of 
missing modes.
It's just going to make things appear more broken and be unexpected to 
userspace.

Maybe this is some new thing that we do now I am out of the loop on...

- Joshie 🐸✨

On 6/23/24 10:20 AM, Joshua Ashton wrote:
> Are you planning on submitting a bogus CVE for this patch too?
> 
> - Joshie 🐸✨
> 
> On June 22, 2024 9:22:19 AM GMT+01:00, Ma Ke <make24 at iscas.ac.cn> wrote:
>> In amdgpu_connector_add_common_modes(), the return value of drm_cvt_mode()
>> is assigned to mode, which will lead to a NULL pointer dereference on
>> failure of drm_cvt_mode(). Add a check to avoid npd.
>>
>> Signed-off-by: Ma Ke <make24 at iscas.ac.cn>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
>> index 9caba10315a8..6cf946adb6fe 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
>> @@ -458,6 +458,8 @@ static void amdgpu_connector_add_common_modes(struct drm_encoder *encoder,
>> 			continue;
>>
>> 		mode = drm_cvt_mode(dev, common_modes[i].w, common_modes[i].h, 60, false, false, false);
>> +		if (!mode)
>> +			continue;
>> 		drm_mode_probed_add(connector, mode);
>> 	}
>> }