[v1] drm/panthor: Fix potential memleak of vma structure

[PATCH] drm/panthor: Fix potential memleak of vma structure

Posted by Akash Goel 3 months, 2 weeks ago

This commit addresses a memleak issue of panthor_vma (or drm_gpuva)
structure in Panthor driver, that can happen if the GPU page table
update operation to map the pages fail.
The issue is very unlikely to occur in practice.

Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
Signed-off-by: Akash Goel <akash.goel@arm.com>
---
 drivers/gpu/drm/panthor/panthor_mmu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 6dec4354e378..34a86f7b58d9 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -2081,8 +2081,10 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv)
 	ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags),
 				   op_ctx->map.sgt, op->map.gem.offset,
 				   op->map.va.range);
-	if (ret)
+	if (ret) {
+		kfree(vma);
 		return ret;
+	}
 
 	/* Ref owned by the mapping now, clear the obj field so we don't release the
 	 * pinning/obj ref behind GPUVA's back.
-- 
2.25.1

Re: [PATCH] drm/panthor: Fix potential memleak of vma structure

Posted by Boris Brezillon 3 months, 2 weeks ago

On Mon, 20 Oct 2025 09:59:14 +0100
Akash Goel <akash.goel@arm.com> wrote:

> This commit addresses a memleak issue of panthor_vma (or drm_gpuva)
> structure in Panthor driver, that can happen if the GPU page table
> update operation to map the pages fail.
> The issue is very unlikely to occur in practice.
> 
> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> Signed-off-by: Akash Goel <akash.goel@arm.com>
> ---
>  drivers/gpu/drm/panthor/panthor_mmu.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index 6dec4354e378..34a86f7b58d9 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -2081,8 +2081,10 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv)
>  	ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags),
>  				   op_ctx->map.sgt, op->map.gem.offset,
>  				   op->map.va.range);
> -	if (ret)
> +	if (ret) {
> +		kfree(vma);

Calling kfree() in this context is probably fine, but I think I'd
prefer if we were introducing a panthor_vm_op_ctx_return_vma() helper
returning the vma to the preallocated array, and letting the deferred
cleanup function free this up.

>  		return ret;
> +	}
>  
>  	/* Ref owned by the mapping now, clear the obj field so we don't release the
>  	 * pinning/obj ref behind GPUVA's back.

Re: [PATCH] drm/panthor: Fix potential memleak of vma structure

Posted by Akash Goel 3 months, 2 weeks ago


On 10/20/25 10:30, Boris Brezillon wrote:
> On Mon, 20 Oct 2025 09:59:14 +0100
> Akash Goel <akash.goel@arm.com> wrote:
> 
>> This commit addresses a memleak issue of panthor_vma (or drm_gpuva)
>> structure in Panthor driver, that can happen if the GPU page table
>> update operation to map the pages fail.
>> The issue is very unlikely to occur in practice.
>>
>> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
>> Signed-off-by: Akash Goel <akash.goel@arm.com>
>> ---
>>   drivers/gpu/drm/panthor/panthor_mmu.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
>> index 6dec4354e378..34a86f7b58d9 100644
>> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
>> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
>> @@ -2081,8 +2081,10 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv)
>>   	ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags),
>>   				   op_ctx->map.sgt, op->map.gem.offset,
>>   				   op->map.va.range);
>> -	if (ret)
>> +	if (ret) {
>> +		kfree(vma);
> 
> Calling kfree() in this context is probably fine, but I think I'd
> prefer if we were introducing a panthor_vm_op_ctx_return_vma() helper
> returning the vma to the preallocated array, and letting the deferred
> cleanup function free this up.


Thanks for the quick review.

So need to do like this, where we search for a NULL entry to store the 
VMA pointer to be returned ?

static void
panthor_vm_op_ctx_return_vma(struct panthor_vm_op_ctx *op_ctx,
			     struct panthor_vma *vma)
{
	for (u32 i = 0; i < ARRAY_SIZE(op_ctx->preallocated_vmas); i++) {
		if (!op_ctx->preallocated_vmas[i]) {
			op_ctx->preallocated_vmas[i] = vma;
			return;
		}
	}
}


Please let me know.

Best regards
Akash

> 
>>   		return ret;
>> +	}
>>   
>>   	/* Ref owned by the mapping now, clear the obj field so we don't release the
>>   	 * pinning/obj ref behind GPUVA's back.
>

Re: [PATCH] drm/panthor: Fix potential memleak of vma structure

Posted by Boris Brezillon 3 months, 2 weeks ago

On Mon, 20 Oct 2025 10:50:19 +0100
Akash Goel <akash.goel@arm.com> wrote:

> On 10/20/25 10:30, Boris Brezillon wrote:
> > On Mon, 20 Oct 2025 09:59:14 +0100
> > Akash Goel <akash.goel@arm.com> wrote:
> >   
> >> This commit addresses a memleak issue of panthor_vma (or drm_gpuva)
> >> structure in Panthor driver, that can happen if the GPU page table
> >> update operation to map the pages fail.
> >> The issue is very unlikely to occur in practice.
> >>
> >> Fixes: 647810ec2476 ("drm/panthor: Add the MMU/VM logical block")
> >> Signed-off-by: Akash Goel <akash.goel@arm.com>
> >> ---
> >>   drivers/gpu/drm/panthor/panthor_mmu.c | 4 +++-
> >>   1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> >> index 6dec4354e378..34a86f7b58d9 100644
> >> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> >> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> >> @@ -2081,8 +2081,10 @@ static int panthor_gpuva_sm_step_map(struct drm_gpuva_op *op, void *priv)
> >>   	ret = panthor_vm_map_pages(vm, op->map.va.addr, flags_to_prot(vma->flags),
> >>   				   op_ctx->map.sgt, op->map.gem.offset,
> >>   				   op->map.va.range);
> >> -	if (ret)
> >> +	if (ret) {
> >> +		kfree(vma);  
> > 
> > Calling kfree() in this context is probably fine, but I think I'd
> > prefer if we were introducing a panthor_vm_op_ctx_return_vma() helper
> > returning the vma to the preallocated array, and letting the deferred
> > cleanup function free this up.  
> 
> 
> Thanks for the quick review.
> 
> So need to do like this, where we search for a NULL entry to store the 
> VMA pointer to be returned ?
> 
> static void
> panthor_vm_op_ctx_return_vma(struct panthor_vm_op_ctx *op_ctx,
> 			     struct panthor_vma *vma)
> {
> 	for (u32 i = 0; i < ARRAY_SIZE(op_ctx->preallocated_vmas); i++) {
> 		if (!op_ctx->preallocated_vmas[i]) {
> 			op_ctx->preallocated_vmas[i] = vma;
> 			return;
> 		}
> 	}
> }
> 
> 
> Please let me know.

Yep, that looks good to me.