Re: [PATCH v2 1/2] drm/panthor: Fix handling of NO_MMAP BOs

[Liviu Dudau <liviu.dudau@arm.com>]

On Tue, Oct 13, 2026 at 01:54:32PM +0100, Akash Goel wrote:
> The BOs created with DRM_PANTHOR_BO_NO_MMAP flag are not supposed to be
> mmappable by the Userspace. But after the rework to support shrinker,
> it became possible to mmap NO_MMAP BOs. Userspace could second guess
> the file offset range, allocated unconditionally at the BO creation
> time, and create a CPU mapping. There may not be any adverse effect of
> such a CPU mapping though.
> This commit adds a check in the mmap callback of Panthor driver to
> fail the mmap() attempts on BOs created with NO_MMAP flag. The check
> covers private BOs as well as the prime exported BOs that are mmapped
> using prime fd.
> 
> v2:
>  - Fix breakage of mmap() on exported BOs that didn't have
>    BO_MMAP_OFFSET ioctl invoked for them.
> 
> Fixes: 68cbf96b1e9b ("drm/panthor: Part ways with drm_gem_shmem_object")
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Akash Goel <akash.goel@arm.com>

Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>

Best regards,
Liviu

> ---
>  drivers/gpu/drm/panthor/panthor_gem.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> index c07a44057e42..22b57ab6f929 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.c
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -744,6 +744,9 @@ static int panthor_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *v
>  	struct panthor_gem_object *bo = to_panthor_bo(obj);
>  	int ret;
>  
> +	if (bo->flags & DRM_PANTHOR_BO_NO_MMAP)
> +		return -EINVAL;
> +
>  	if (drm_gem_is_imported(obj)) {
>  		/* Reset both vm_ops and vm_private_data, so we don't end up with
>  		 * vm_ops pointing to our implementation if the dma-buf backend
> -- 
> 2.25.1
> 

-- 
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