[PATCH] drm/amd/display: fix dereference before NULL check

[PATCH] drm/amd/display: fix dereference before NULL check

[José Expósito]

The "plane_state" pointer was access before checking if it was NULL.

Avoid a possible NULL pointer dereference by accessing the plane
address after the check.

Addresses-Coverity-ID: 1474582 ("Dereference before null check")
Fixes: 3f68c01be9a22 ("drm/amd/display: add cyan_skillfish display support")
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
index cfd09b3f705e..fe22530242d2 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
@@ -134,11 +134,12 @@ void dcn201_update_plane_addr(const struct dc *dc, struct pipe_ctx *pipe_ctx)
 	PHYSICAL_ADDRESS_LOC addr;
 	struct dc_plane_state *plane_state = pipe_ctx->plane_state;
 	struct dce_hwseq *hws = dc->hwseq;
-	struct dc_plane_address uma = plane_state->address;
+	struct dc_plane_address uma;
 
 	if (plane_state == NULL)
 		return;
 
+	uma = plane_state->address;
 	addr_patched = patch_address_for_sbs_tb_stereo(pipe_ctx, &addr);
 
 	plane_address_in_gpu_space_to_uma(hws, &uma);
-- 
2.25.1

Re: [PATCH] drm/amd/display: fix dereference before NULL check

[Harry Wentland]

On 2021-12-16 13:14, José Expósito wrote:
> The "plane_state" pointer was access before checking if it was NULL.
> 
> Avoid a possible NULL pointer dereference by accessing the plane
> address after the check.
> 
> Addresses-Coverity-ID: 1474582 ("Dereference before null check")
> Fixes: 3f68c01be9a22 ("drm/amd/display: add cyan_skillfish display support")
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
>  drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> index cfd09b3f705e..fe22530242d2 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> +++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_hwseq.c
> @@ -134,11 +134,12 @@ void dcn201_update_plane_addr(const struct dc *dc, struct pipe_ctx *pipe_ctx)
>  	PHYSICAL_ADDRESS_LOC addr;
>  	struct dc_plane_state *plane_state = pipe_ctx->plane_state;
>  	struct dce_hwseq *hws = dc->hwseq;
> -	struct dc_plane_address uma = plane_state->address;
> +	struct dc_plane_address uma;
>  
>  	if (plane_state == NULL)
>  		return;
>  
> +	uma = plane_state->address;
>  	addr_patched = patch_address_for_sbs_tb_stereo(pipe_ctx, &addr);
>  
>  	plane_address_in_gpu_space_to_uma(hws, &uma);