[PATCH] drm: Set vm_ops to GEM object's values during mmap

[Thomas Zimmermann]

Hi

Am 15.01.21 um 10:17 schrieb Kieran Bingham:
> Hi Thomas,
> 
> On 15/01/2021 08:39, Thomas Zimmermann wrote:
>> The GEM mmap code relies on the GEM object's mmap callback to set the
>> VMA's vm_ops field. This is easily forgotten and lead to a memory leak
> 
>   s/lead/can lead/
> 
>> in the CMA helpers. Instead set the vm_ops field in the DRM core code
>> to the GEM object's value. Drivers with different needs can override
>> this in their mmap callback.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> Fixes: f5ca8eb6f9bd ("drm/cma-helper: Implement mmap as GEM CMA object functions")
>> Reported-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>
> 
> This also works here.
>   - https://paste.ubuntu.com/p/S2Q586rgwT/
> 
> Tested-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>

Great! I have to send out another iteration of the patch, but I think 
the change is such that I can keep the Tested-by.

Best regards
Thomas

> 
>> Cc: Maxime Ripard <mripard at kernel.org>
>> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
>> Cc: David Airlie <airlied at linux.ie>
>> Cc: Daniel Vetter <daniel at ffwll.ch>
>> Cc: Eric Anholt <eric at anholt.net>
>> Cc: dri-devel at lists.freedesktop.org
>> ---
>>   drivers/gpu/drm/drm_gem.c   | 23 ++++++++++++-----------
>>   drivers/gpu/drm/drm_prime.c |  4 ++++
>>   2 files changed, 16 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
>> index 34b2f111c01c..54d95621fcbb 100644
>> --- a/drivers/gpu/drm/drm_gem.c
>> +++ b/drivers/gpu/drm/drm_gem.c
>> @@ -1069,27 +1069,28 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
>>   
>>   	vma->vm_private_data = obj;
>>   
>> +	if (!obj->funcs->vm_ops) {
>> +		ret = -EINVAL;
>> +		goto err_drm_gem_object_put;
>> +	}
>> +	vma->vm_ops = obj->funcs->vm_ops;
>> +
>>   	if (obj->funcs->mmap) {
>>   		ret = obj->funcs->mmap(obj, vma);
>> -		if (ret) {
>> -			drm_gem_object_put(obj);
>> -			return ret;
>> -		}
>> +		if (ret)
>> +			goto err_drm_gem_object_put;
>>   		WARN_ON(!(vma->vm_flags & VM_DONTEXPAND));
>>   	} else {
>> -		if (obj->funcs->vm_ops)
>> -			vma->vm_ops = obj->funcs->vm_ops;
>> -		else {
>> -			drm_gem_object_put(obj);
>> -			return -EINVAL;
>> -		}
>> -
>>   		vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
>>   		vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
>>   		vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>>   	}
>>   
>>   	return 0;
>> +
>> +err_drm_gem_object_put:
>> +	drm_gem_object_put(obj);
>> +	return ret;
>>   }
>>   EXPORT_SYMBOL(drm_gem_mmap_obj);
>>   
>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>> index 683aa29ecd3b..0549ec190583 100644
>> --- a/drivers/gpu/drm/drm_prime.c
>> +++ b/drivers/gpu/drm/drm_prime.c
>> @@ -717,6 +717,10 @@ int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
>>   	vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
>>   
>>   	if (obj->funcs && obj->funcs->mmap) {
>> +		if (!obj->funcs->vm_ops)
>> +			return -EINVAL;
>> +		vma->vm_ops = obj->funcs->vm_ops;
>> +
>>   		ret = obj->funcs->mmap(obj, vma);
>>   		if (ret)
>>   			return ret;
>>
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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