RE: [PATCH] drm/amd/amdkfd: Fix a resource leak in svm_range_validate_and_map()

["Errabolu, Ramesh" <Ramesh.Errabolu@xxxxxxx>]

[AMD Official Use Only - General]

Good catch on dropping return values

Regards,
Ramesh

-----Original Message-----
From: Kuehling, Felix <Felix.Kuehling@xxxxxxx>
Sent: Thursday, May 2, 2024 12:30 AM
To: Errabolu, Ramesh <Ramesh.Errabolu@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [PATCH] drm/amd/amdkfd: Fix a resource leak in svm_range_validate_and_map()


On 2024-05-01 14:34, Felix Kuehling wrote:
>
>
> On 2024-04-30 19:29, Ramesh Errabolu wrote:
>> Analysis of code by Coverity, a static code analyser, has identified
>> a resource leak in the symbol hmm_range. This leak occurs when one of
>> the prior steps before it is released encounters an error.
>>
>> Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu@xxxxxxx>
>> ---
>>   drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>> b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>> index 386875e6eb96..dcb1d5d3f860 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>> @@ -1658,7 +1658,7 @@ static int svm_range_validate_and_map(struct
>> mm_struct *mm,
>>       start = map_start << PAGE_SHIFT;
>>       end = (map_last + 1) << PAGE_SHIFT;
>>       for (addr = start; !r && addr < end; ) {
>> -        struct hmm_range *hmm_range;
>> +        struct hmm_range *hmm_range = NULL;
>>           unsigned long map_start_vma;
>>           unsigned long map_last_vma;
>>           struct vm_area_struct *vma; @@ -1696,7 +1696,9 @@ static
>> int svm_range_validate_and_map(struct mm_struct *mm,
>>           }
>>           svm_range_lock(prange);
>> -        if (!r && amdgpu_hmm_range_get_pages_done(hmm_range)) {
>> +
>> +        // Free backing memory of hmm_range if it was initialized
>> +        if (hmm_range && amdgpu_hmm_range_get_pages_done(hmm_range))
>> +{
>>               pr_debug("hmm update the range, need validate
>> again\n");
>>               r = -EAGAIN;
>
> Nack! This can now override other error codes that aren't meant to be
> overridden with -EAGAIN.
>
> I think a better solution would be to just revserse this condition to
> ensure that amdgpu_hmm_range_get_pages_done is always called:
>
>          if (amdgpu_hmm_range_get_pages_done(hmm_range) && !r) {

Correction: You still need the NULL check:

                if (hmm_range &&
                    amdgpu_hmm_range_get_pages_done(hmm_range) &&
                    !r) {
                        ...
                }

Regards,
   Felix

>              ...
>              r = -EAGAIN;
>          }
>
> Regards,
>    Felix
>
>>           }