[PATCH] drm/panthor: Fix NULL vs IS_ERR() bug in panthor_ioctl_tiler_heap_destroy()

[PATCH] drm/panthor: Fix NULL vs IS_ERR() bug in panthor_ioctl_tiler_heap_destroy()

[Harshit Mogalapalli]

panthor_vm_get_heap_pool() returns ERR_PTR on failure.

Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
---
This is spotted by smatch and the patch is only compile tested
---
 drivers/gpu/drm/panthor/panthor_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index 11b3ccd58f85..050b905b0453 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
 		return -EINVAL;
 
 	pool = panthor_vm_get_heap_pool(vm, false);
-	if (!pool) {
-		ret = -EINVAL;
+	if (IS_ERR(pool)) {
+		ret = PTR_ERR(pool);
 		goto out_put_vm;
 	}
 
-- 
2.39.3

Re: [PATCH] drm/panthor: Fix NULL vs IS_ERR() bug in panthor_ioctl_tiler_heap_destroy()

[Boris Brezillon]

Hello Harshit,

On Tue,  2 Apr 2024 03:33:58 -0700
Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> wrote:

> panthor_vm_get_heap_pool() returns ERR_PTR on failure.
> 
> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
> ---
> This is spotted by smatch and the patch is only compile tested
> ---
>  drivers/gpu/drm/panthor/panthor_drv.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index 11b3ccd58f85..050b905b0453 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
>  		return -EINVAL;
>  
>  	pool = panthor_vm_get_heap_pool(vm, false);
> -	if (!pool) {
> -		ret = -EINVAL;
> +	if (IS_ERR(pool)) {
> +		ret = PTR_ERR(pool);

Actually, panthor_vm_get_heap_pool() will return NULL if there's no
heap pool attached to this VM and create=false, so this was correct.
This being said, I'm fine making that consistent by returning
ERR_PTR(-ENOENT) instead of NULL in that case. This way we don't have
two different semantics based on the 'create' value.

Oh, and please merge everything into a single patch instead of one patch
per call-site.

Regards,

Boris

>  		goto out_put_vm;
>  	}
>  

Re: [PATCH] drm/panthor: Fix NULL vs IS_ERR() bug in panthor_ioctl_tiler_heap_destroy()

[Harshit Mogalapalli]

Hello Boris,

On 02/04/24 18:03, Boris Brezillon wrote:
> Hello Harshit,
> 
> On Tue,  2 Apr 2024 03:33:58 -0700
> Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> wrote:
> 
>> panthor_vm_get_heap_pool() returns ERR_PTR on failure.
>>
>> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
>> ---
>> This is spotted by smatch and the patch is only compile tested
>> ---
>>   drivers/gpu/drm/panthor/panthor_drv.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
>> index 11b3ccd58f85..050b905b0453 100644
>> --- a/drivers/gpu/drm/panthor/panthor_drv.c
>> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
>> @@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
>>   		return -EINVAL;
>>   
>>   	pool = panthor_vm_get_heap_pool(vm, false);
>> -	if (!pool) {
>> -		ret = -EINVAL;
>> +	if (IS_ERR(pool)) {
>> +		ret = PTR_ERR(pool);
> 
> Actually, panthor_vm_get_heap_pool() will return NULL if there's no
> heap pool attached to this VM and create=false, so this was correct.
> This being said, I'm fine making that consistent by returning
> ERR_PTR(-ENOENT) instead of NULL in that case. This way we don't have
> two different semantics based on the 'create' value.
> 

Thanks for explaining. I missed the case where create is false and there 
is no heap pool attached, so panthor_vm_get_heap_pool() can return NULL.

1878  *
1879  * Return: A valid pointer on success, an ERR_PTR() otherwise.
1880  */
1881 struct panthor_heap_pool *panthor_vm_get_heap_pool(struct 
panthor_vm *vm, bool create)

The documentation says it returns ERR_PTR() on failure, so is it worth 
doing something like:

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c 
b/drivers/gpu/drm/panthor/panthor_mmu.c
index fdd35249169f..e1285cdb09ff 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1893,6 +1893,8 @@ struct panthor_heap_pool 
*panthor_vm_get_heap_pool(struct panthor_vm *vm, bool c
                         vm->heaps.pool = panthor_heap_pool_get(pool);
         } else {
                 pool = panthor_heap_pool_get(vm->heaps.pool);
+               if (!pool)
+                       pool = ERR_PTR(-ENOENT);
         }
         mutex_unlock(&vm->heaps.lock);


and change all callers of panthor_vm_get_heap_pool() to only check for 
IS_ERR() ?


> Oh, and please merge everything into a single patch instead of one patch
> per call-site.
> 

Sure, I noticed one after the other. I will fix them together in v2.

Thanks,
Harshit
> Regards,
> 
> Boris
> 
>>   		goto out_put_vm;
>>   	}
>>   
> 

Re: [PATCH] drm/panthor: Fix NULL vs IS_ERR() bug in panthor_ioctl_tiler_heap_destroy()

[Boris Brezillon]

On Tue, 2 Apr 2024 18:52:12 +0530
Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> wrote:

> Hello Boris,
> 
> On 02/04/24 18:03, Boris Brezillon wrote:
> > Hello Harshit,
> > 
> > On Tue,  2 Apr 2024 03:33:58 -0700
> > Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> wrote:
> >   
> >> panthor_vm_get_heap_pool() returns ERR_PTR on failure.
> >>
> >> Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
> >> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
> >> ---
> >> This is spotted by smatch and the patch is only compile tested
> >> ---
> >>   drivers/gpu/drm/panthor/panthor_drv.c | 4 ++--
> >>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> >> index 11b3ccd58f85..050b905b0453 100644
> >> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> >> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> >> @@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
> >>   		return -EINVAL;
> >>   
> >>   	pool = panthor_vm_get_heap_pool(vm, false);
> >> -	if (!pool) {
> >> -		ret = -EINVAL;
> >> +	if (IS_ERR(pool)) {
> >> +		ret = PTR_ERR(pool);  
> > 
> > Actually, panthor_vm_get_heap_pool() will return NULL if there's no
> > heap pool attached to this VM and create=false, so this was correct.
> > This being said, I'm fine making that consistent by returning
> > ERR_PTR(-ENOENT) instead of NULL in that case. This way we don't have
> > two different semantics based on the 'create' value.
> >   
> 
> Thanks for explaining. I missed the case where create is false and there 
> is no heap pool attached, so panthor_vm_get_heap_pool() can return NULL.
> 
> 1878  *
> 1879  * Return: A valid pointer on success, an ERR_PTR() otherwise.
> 1880  */
> 1881 struct panthor_heap_pool *panthor_vm_get_heap_pool(struct 
> panthor_vm *vm, bool create)
> 
> The documentation says it returns ERR_PTR() on failure, so is it worth 
> doing something like:
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c 
> b/drivers/gpu/drm/panthor/panthor_mmu.c
> index fdd35249169f..e1285cdb09ff 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -1893,6 +1893,8 @@ struct panthor_heap_pool 
> *panthor_vm_get_heap_pool(struct panthor_vm *vm, bool c
>                          vm->heaps.pool = panthor_heap_pool_get(pool);
>          } else {
>                  pool = panthor_heap_pool_get(vm->heaps.pool);
> +               if (!pool)
> +                       pool = ERR_PTR(-ENOENT);
>          }
>          mutex_unlock(&vm->heaps.lock);
> 
> 
> and change all callers of panthor_vm_get_heap_pool() to only check for 
> IS_ERR() ?

Yep, that's what I had in mind.

> 
> 
> > Oh, and please merge everything into a single patch instead of one patch
> > per call-site.
> >   
> 
> Sure, I noticed one after the other. I will fix them together in v2.

Great!

Thanks,

Boris