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

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Date:   Thu, 16 Dec 2021 19:14:43 +0100
From:   José Expósito <jose.exposito89@...il.com>
To:     harry.wentland@....com
Cc:     sunpeng.li@....com, Rodrigo.Siqueira@....com,
        alexander.deucher@....com, christian.koenig@....com,
        Xinhui.Pan@....com, airlied@...ux.ie, charlene.liu@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        José Expósito <jose.exposito89@...il.com>
Subject: [PATCH] drm/amd/display: fix dereference before NULL check

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@...il.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