From 16ce8fd94da8599bb6f0496895d392a69aead1c0 Mon Sep 17 00:00:00 2001
From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Date: Sun, 21 Jul 2024 19:18:58 +0530
Subject: [PATCH] drm/amd/display: Add null check for head_pipe in
 dcn201_acquire_free_pipe_for_layer

commit f22f4754aaa47d8c59f166ba3042182859e5dff7 upstream.

This commit addresses a potential null pointer dereference issue in the
`dcn201_acquire_free_pipe_for_layer` function. The issue could occur
when `head_pipe` is null.

The fix adds a check to ensure `head_pipe` is not null before asserting
it. If `head_pipe` is null, the function returns NULL to prevent a
potential null pointer dereference.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn201/dcn201_resource.c:1016 dcn201_acquire_free_pipe_for_layer() error: we previously assumed 'head_pipe' could be null (see line 1010)

Cc: Tom Chung <chiahsuan.chung@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[ dcn201 was moved from drivers/gpu/drm/amd/display/dc to
  drivers/gpu/drm/amd/display/dc/resource since commit
  8b8eed05a1c6 ("drm/amd/display: Refactor resource into component directory").
  The path is changed accordingly to apply the patch on 6.6.y. ]
Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/dcn201/dcn201_resource.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_resource.c b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_resource.c
index 2dc4d2c1410b..8efe3f32a0e7 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn201/dcn201_resource.c
@@ -1002,8 +1002,10 @@ static struct pipe_ctx *dcn201_acquire_free_pipe_for_layer(
 	struct pipe_ctx *head_pipe = resource_get_otg_master_for_stream(res_ctx, opp_head_pipe->stream);
 	struct pipe_ctx *idle_pipe = resource_find_free_secondary_pipe_legacy(res_ctx, pool, head_pipe);
 
-	if (!head_pipe)
+	if (!head_pipe) {
 		ASSERT(0);
+		return NULL;
+	}
 
 	if (!idle_pipe)
 		return NULL;