[PATCH] drm/amdgpu: fix potential null dereference

[Christian König]

Looks like my response never made it through.

This change and the existing check is nonsense. The caller makes sure 
that ctx is never NULL here.

So the check should probably just be dropped entirely.

Regards,
Christian.

Am 02.03.22 um 15:21 schrieb Alex Deucher:
> Applied.  Thanks!
>
> Alex
>
> On Wed, Mar 2, 2022 at 3:56 AM Weiguo Li <liwg06 at foxmail.com> wrote:
>> "ctx" is dereferenced but null checked later. Swap their positions
>> to avoid potential null dereference.
>>
>> Found using a Coccinelle script:
>> https://coccinelle.gitlabpages.inria.fr/website/rules/mini_null_ref.cocci
>>
>> Signed-off-by: Weiguo Li <liwg06 at foxmail.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> index f522b52725e4..b4f035ce44bc 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> @@ -258,11 +258,12 @@ static void amdgpu_ctx_fini_entity(struct amdgpu_ctx_entity *entity)
>>   static int amdgpu_ctx_get_stable_pstate(struct amdgpu_ctx *ctx,
>>                                          u32 *stable_pstate)
>>   {
>> -       struct amdgpu_device *adev = ctx->adev;
>> +       struct amdgpu_device *adev;
>>          enum amd_dpm_forced_level current_level;
>>
>>          if (!ctx)
>>                  return -EINVAL;
>> +       adev = ctx->adev;
>>
>>          current_level = amdgpu_dpm_get_performance_level(adev);
>>
>> @@ -289,12 +290,13 @@ static int amdgpu_ctx_get_stable_pstate(struct amdgpu_ctx *ctx,
>>   static int amdgpu_ctx_set_stable_pstate(struct amdgpu_ctx *ctx,
>>                                          u32 stable_pstate)
>>   {
>> -       struct amdgpu_device *adev = ctx->adev;
>> +       struct amdgpu_device *adev;
>>          enum amd_dpm_forced_level level;
>>          int r;
>>
>>          if (!ctx)
>>                  return -EINVAL;
>> +       adev = ctx->adev;
>>
>>          mutex_lock(&adev->pm.stable_pstate_ctx_lock);
>>          if (adev->pm.stable_pstate_ctx && adev->pm.stable_pstate_ctx != ctx) {
>> --
>> 2.25.1
>>