Re: [PATCH v2 1/2] drm/xe/ufence: Prefetch ufence addr to catch bogus address

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Oct 16, 2024 at 10:23:03AM +0200, Nirmoy Das wrote:
> access_ok() only checks for addr overflow so also try to read the addr
> to catch invalid addr sent from userspace.
> 
> Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/1630
> Cc: Francois Dugast <francois.dugast@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_sync.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c
> index c6cf227ead40..2e72c06fd40d 100644
> --- a/drivers/gpu/drm/xe/xe_sync.c
> +++ b/drivers/gpu/drm/xe/xe_sync.c
> @@ -54,8 +54,9 @@ static struct xe_user_fence *user_fence_create(struct xe_device *xe, u64 addr,
>  {
>  	struct xe_user_fence *ufence;
>  	u64 __user *ptr = u64_to_user_ptr(addr);
> +	u64 __maybe_unused prefetch_val;
>  
> -	if (!access_ok(ptr, sizeof(*ptr)))
> +	if (get_user(prefetch_val, ptr))
>  		return ERR_PTR(-EFAULT);
>  
>  	ufence = kzalloc(sizeof(*ufence), GFP_KERNEL);
> -- 
> 2.46.0
>