Re: [PATCH 1/2] drm/radeon: forbid mapping of userptr bo through radeon device file

["Christian König" <deathsimple@vodafone.de>]

There are also checks in (amdgpu|radeon)_gem_mmap_ioctl() to prevent 
this as well.

But it shouldn't hurt us to check that here as well. So both patches are 
Reviewed-by: Christian König <christian.koenig@amd.com>

Regards,
Christian.

Am 19.04.2016 um 15:07 schrieb Jérôme Glisse:
> Allowing userptr bo which are basicly a list of page from some vma
> (so either anonymous page or file backed page) would lead to serious
> corruption of kernel structures and counters (because we overwrite
> the page->mapping field when mapping buffer).
>
> This will already block if the buffer was populated before anyone does
> try to mmap it because then TTM_PAGE_FLAG_SG would be set in in the
> ttm_tt flags. But that flag is check before ttm_tt_populate in the ttm
> vm fault handler.
>
> So to be safe just add a check to verify_access() callback.
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: <stable@vger.kernel.org>
> ---
>   drivers/gpu/drm/radeon/radeon_ttm.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> index 7dddfdc..90f7394 100644
> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> @@ -235,6 +235,8 @@ static int radeon_verify_access(struct ttm_buffer_object *bo, struct file *filp)
>   {
>   	struct radeon_bo *rbo = container_of(bo, struct radeon_bo, tbo);
>   
> +	if (radeon_ttm_tt_has_userptr(bo->ttm))
> +		return -EPERM;
>   	return drm_vma_node_verify_access(&rbo->gem_base.vma_node, filp);
>   }
>   

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