drm/amdkfd: Fix potential deallocation of previously deallocated memory.

  Pointer mqd_mem_obj can be deallocated in kfd_gtt_sa_allocate().
The function then returns non-zero value, which causes the second deallocation.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
---
 drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
  

Hi Daniil,

On Mon, Apr 17, 2023 at 11:55:21PM -0700, Daniil Dulov wrote:
> Pointer mqd_mem_obj can be deallocated in kfd_gtt_sa_allocate().
> The function then returns non-zero value, which causes the second deallocation.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
> Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> index 3b6f5963180d..bce11c5b07d6 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> @@ -119,7 +119,8 @@ static struct kfd_mem_obj *allocate_mqd(struct kfd_dev *kfd,
>  	}
>  
>  	if (retval) {
> -		kfree(mqd_mem_obj);
> +		if (mqd_mem_obj)
> +			kfree(mqd_mem_obj);

I think this is not needed. kfree() returns immediately if
mqd_mem_obj is NULL.

Andi

>  		return NULL;
>  	}
>  
> -- 
> 2.25.1
  

On 18/04/2023 10:47, Andi Shyti wrote:
> Hi Daniil,
> 
> On Mon, Apr 17, 2023 at 11:55:21PM -0700, Daniil Dulov wrote:
>> Pointer mqd_mem_obj can be deallocated in kfd_gtt_sa_allocate().
>> The function then returns non-zero value, which causes the second deallocation.
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
>> Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
>> ---
>>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> index 3b6f5963180d..bce11c5b07d6 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> @@ -119,7 +119,8 @@ static struct kfd_mem_obj *allocate_mqd(struct kfd_dev *kfd,
>>  	}
>>  
>>  	if (retval) {
>> -		kfree(mqd_mem_obj);
>> +		if (mqd_mem_obj)
>> +			kfree(mqd_mem_obj);
> 
> I think this is not needed. kfree() returns immediately if
> mqd_mem_obj is NULL.
> 

Yep, the tool has to be fixed because such patch is just misleading.
However different point - the commit description actually describes
entirely different case: double free. Maybe the issue is true, just the
fix is wrong?

Best regards,
Krzysztof
  

On Tue, Apr 18, 2023 at 12:07:15PM +0200, Krzysztof Kozlowski wrote:
> On 18/04/2023 10:47, Andi Shyti wrote:
> > Hi Daniil,
> > 
> > On Mon, Apr 17, 2023 at 11:55:21PM -0700, Daniil Dulov wrote:
> >> Pointer mqd_mem_obj can be deallocated in kfd_gtt_sa_allocate().
> >> The function then returns non-zero value, which causes the second deallocation.
> >>
> >> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >>
> >> Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
> >> Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
> >> ---
> >>  drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> >> index 3b6f5963180d..bce11c5b07d6 100644
> >> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> >> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
> >> @@ -119,7 +119,8 @@ static struct kfd_mem_obj *allocate_mqd(struct kfd_dev *kfd,
> >>  	}
> >>  
> >>  	if (retval) {
> >> -		kfree(mqd_mem_obj);
> >> +		if (mqd_mem_obj)
> >> +			kfree(mqd_mem_obj);
> > 
> > I think this is not needed. kfree() returns immediately if
> > mqd_mem_obj is NULL.
> > 
> 
> Yep, the tool has to be fixed because such patch is just misleading.
> However different point - the commit description actually describes
> entirely different case: double free. Maybe the issue is true, just the
> fix is wrong?

Yes, indeed, the fix is wrong, but the bug exists. I'm pasting
the original function:

	if (kfd->cwsr_enabled && (q->type == KFD_QUEUE_TYPE_COMPUTE)) {
		mqd_mem_obj = kzalloc(sizeof(struct kfd_mem_obj), GFP_KERNEL);
		if (!mqd_mem_obj)
			return NULL;
		...
	} else {
		retval = kfd_gtt_sa_allocate(kfd, sizeof(struct v9_mqd),
				&mqd_mem_obj);
	}

	if (retval) {
		kfree(mqd_mem_obj);
		return NULL;
	}

The "kfd_gtt_sa_allocate()" function allocates mqd_mem_obj and if
an error occurs internally frees it, without setting it to NULL;
retval is true and we kfree a memory that has already been freed.

The real fix is to move the "if (retval)" inside the if. It would
basically be:

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
index fdbfd725841ff..31d47d687bd62 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
@@ -115,18 +115,20 @@ static struct kfd_mem_obj *allocate_mqd(struct kfd_dev *kfd,
                        &(mqd_mem_obj->gtt_mem),
                        &(mqd_mem_obj->gpu_addr),
                        (void *)&(mqd_mem_obj->cpu_ptr), true);
+
+               if (retval) {
+                       kfree(mqd_mem_obj);
+                       return NULL;
+               }
+
        } else {
                retval = kfd_gtt_sa_allocate(kfd, sizeof(struct v9_mqd),
                                &mqd_mem_obj);
-       }
-
-       if (retval) {
-               kfree(mqd_mem_obj);
-               return NULL;
+               if (retval)
+                       return NULL;
        }
 
        return mqd_mem_obj;
-
 }

Maybe with some clever refactoring we could reduce some code
duplication.

Daniil will you look into this?

Andi
  

> Daniil will you look into this?

and, because this is a bug fix, if you do want to send a real
fix, plase add to the commit message:

Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
Cc: Oak Zeng <oak.zeng@intel.com>
Cc: <stable@vger.kernel.org> # v5.3+

Andi

PS: please note that Oak's e-mail has changed.
  

Thank you for your feedback! I will do it as soon as possible.

Daniil

________________________________
От: Andi Shyti <andi.shyti@linux.intel.com>
Отправлено: вторник, 18 апреля 2023 г., 20:44
Кому: Andi Shyti <andi.shyti@linux.intel.com>
Копия: Krzysztof Kozlowski <krzk@kernel.org>; Daniil Dulov <D.Dulov@aladdin.ru>; Felix Kuehling <Felix.Kuehling@amd.com>; lvc-project@linuxtesting.org <lvc-project@linuxtesting.org>; David Airlie <airlied@linux.ie>; linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>; Alex Deucher <alexander.deucher@amd.com>; Oak Zeng <oak.zeng@intel.com>; Christian König <christian.koenig@amd.com>
Тема: Re: [PATCH] drm/amdkfd: Fix potential deallocation of previously deallocated memory.

> Daniil will you look into this?

and, because this is a bug fix, if you do want to send a real
fix, plase add to the commit message:

Fixes: d1f8f0d17d40 ("drm/amdkfd: Move non-sdma mqd allocation out of init_mqd")
Cc: Oak Zeng <oak.zeng@intel.com>
Cc: <stable@vger.kernel.org> # v5.3+

Andi

PS: please note that Oak's e-mail has changed.