Re: [PATCH] drm/fence: fix memory overwrite when setting out_fence fd

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Gustavo,

Thank you for the patch.

On Friday 13 Jan 2017 12:22:09 Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.com>
> 
> Currently if the userspace declares a int variable to store the out_fence
> fd and pass it to OUT_FENCE_PTR the kernel will overwrite the 32 bits
> above the int variable on 64 bits systems.
> 
> Fix this by making the internal storage of out_fence in the kernel a s32
> pointer.
> 
> Reported-by: Chad Versace <chadversary@chromium.org>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Rafael Antognolli <rafael.antognolli@intel.com>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> Cc: stable@vger.kernel.org

I don't think this is needed, given that the code was merged in v4.10-rc1, and 
this patch should be merged as a v4.10-rc fix.

> ---
>  drivers/gpu/drm/drm_atomic.c  | 12 ++++++------
>  include/drm/drm_atomic.h      |  2 +-
>  include/drm/drm_mode_config.h |  2 +-
>  3 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 6414bcf..723392f 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -286,15 +286,15 @@ drm_atomic_get_crtc_state(struct drm_atomic_state
> *state, EXPORT_SYMBOL(drm_atomic_get_crtc_state);
> 
>  static void set_out_fence_for_crtc(struct drm_atomic_state *state,
> -				   struct drm_crtc *crtc, s64 __user 
*fence_ptr)
> +				   struct drm_crtc *crtc, s32 __user 
*fence_ptr)
>  {
>  	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = fence_ptr;
>  }
> 
> -static s64 __user *get_out_fence_for_crtc(struct drm_atomic_state *state,
> +static s32 __user *get_out_fence_for_crtc(struct drm_atomic_state *state,
>  					  struct drm_crtc *crtc)
>  {
> -	s64 __user *fence_ptr;
> +	s32 __user *fence_ptr;
> 
>  	fence_ptr = state->crtcs[drm_crtc_index(crtc)].out_fence_ptr;
>  	state->crtcs[drm_crtc_index(crtc)].out_fence_ptr = NULL;
> @@ -507,7 +507,7 @@ int drm_atomic_crtc_set_property(struct drm_crtc *crtc,
>  		state->color_mgmt_changed |= replaced;
>  		return ret;
>  	} else if (property == config->prop_out_fence_ptr) {
> -		s64 __user *fence_ptr = u64_to_user_ptr(val);
> +		s32 __user *fence_ptr = u64_to_user_ptr(val);
> 
>  		if (!fence_ptr)
>  			return 0;
> @@ -1914,7 +1914,7 @@ EXPORT_SYMBOL(drm_atomic_clean_old_fb);
>   */
> 
>  struct drm_out_fence_state {
> -	s64 __user *out_fence_ptr;
> +	s32 __user *out_fence_ptr;
>  	struct sync_file *sync_file;
>  	int fd;
>  };
> @@ -1951,7 +1951,7 @@ static int prepare_crtc_signaling(struct drm_device
> *dev, return 0;
> 
>  	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -		u64 __user *fence_ptr;
> +		s32 __user *fence_ptr;
> 
>  		fence_ptr = get_out_fence_for_crtc(crtc_state->state, crtc);
> 
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index f96220e..f1cb2b0 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -144,7 +144,7 @@ struct __drm_crtcs_state {
>  	struct drm_crtc *ptr;
>  	struct drm_crtc_state *state;
>  	struct drm_crtc_commit *commit;
> -	s64 __user *out_fence_ptr;
> +	s32 __user *out_fence_ptr;
>  	unsigned last_vblank_count;
>  };
> 
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 17942c0..fe230f1 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -496,7 +496,7 @@ struct drm_mode_config {
>  	/**
>  	 * @prop_out_fence_ptr: Sync File fd pointer representing the
>  	 * outgoing fences for a CRTC. Userspace should provide a pointer to a
> -	 * value of type s64, and then cast that pointer to u64.
> +	 * value of type s32, and then cast that pointer to u64.
>  	 */
>  	struct drm_property *prop_out_fence_ptr;
>  	/**

-- 
Regards,

Laurent Pinchart