[Intel-gfx] Potential NULL pointer dereference in intel_crt_get_edid

[Shaobo He]

Hi Rodrigo,

Sorry I'm a bit lost here. May I ask where the `WARN` is?

Thanks,
Shaobo
On 3/18/19 5:26 PM, Rodrigo Vivi wrote:
> Hi Shaobo,
> 
> n Mon, Mar 18, 2019 at 05:01:10PM -0600, Shaobo He wrote:
>> Hello everyone,
>>
>> My name is Shaobo He and I am a graduate student at University of Utah. I am
>> using a static analysis tool to search for null pointer dereferences and
>> came across a potentially invalid memory access in the file
>> drivers/gpu/drm/i915/intel_crt.c: in function `intel_crt_detect_ddc`,
>> function `intel_gmbus_get_adapter` can return a NULL pointer which is
> 
> if this happens we've done a terrible job on defining the platform...
> 
>> dereferenced by the call to `drm_get_edid` or `intel_gmbus_is_forced_bit`.
> 
> but it seems you are right... this will reach i2c_transfer in the end
> and it will break everything after we gave the Warning...
> 
>> It seems that the return value of `intel_gmbus_get_adapter` is never
>> NULL-checked. If so, it would be better to replace the branch to return a
>> NULL pointer with something like `BUG_ON`.
> 
> what about just adding if (!i2c) return false
> instead of BUG.
> 
> We already have the WARN to debug if this case ever happens.
> 
> Thanks,
> Rodrigo.
> 
>>
>> Please let me know if it makes sense. I am looking forward to your reply.
>>
>> Best,
>> Shaobo