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

[Felix Kuehling <felix.kuehling@amd.com>]

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@amd.com>
> ---
>   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) {
			...
			r = -EAGAIN;
		}

Regards,
   Felix

>   		}