linux-kernel - [PATCH 6.1/6.6] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in

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Message-ID: <20250729114924.138111-1-d.dulov@aladdin.ru>
Date: Tue, 29 Jul 2025 14:49:24 +0300
From: Daniil Dulov <d.dulov@...ddin.ru>
To: <stable@...r.kernel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Daniil Dulov <d.dulov@...ddin.ru>, Harry Wentland
	<harry.wentland@....com>, Leo Li <sunpeng.li@....com>, Rodrigo Siqueira
	<siqueira@...lia.com>, Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>, David Airlie
	<airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	<amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <lvc-project@...uxtesting.org>, Tom Chung
	<chiahsuan.chung@....com>, Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
	"Roman Li" <roman.li@....com>, Alex Hung <alex.hung@....com>, Aurabindo
 Pillai <aurabindo.pillai@....com>, Hamza Mahfooz <hamza.mahfooz@....com>,
	"Srinivasan Shanmugam" <srinivasan.shanmugam@....com>
Subject: [PATCH 6.1/6.6] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

From: Srinivasan Shanmugam <srinivasan.shanmugam@....com>

commit ac2140449184a26eac99585b7f69814bd3ba8f2d upstream.

This commit addresses a potential null pointer dereference issue in the
`dcn32_acquire_idle_pipe_for_head_pipe_in_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/dcn32/dcn32_resource.c:2690 dcn32_acquire_idle_pipe_for_head_pipe_in_layer() error: we previously assumed 'head_pipe' could be null (see line 2681)

Cc: Tom Chung <chiahsuan.chung@....com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Cc: Roman Li <roman.li@....com>
Cc: Alex Hung <alex.hung@....com>
Cc: Aurabindo Pillai <aurabindo.pillai@....com>
Cc: Harry Wentland <harry.wentland@....com>
Cc: Hamza Mahfooz <hamza.mahfooz@....com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@....com>
Reviewed-by: Tom Chung <chiahsuan.chung@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
[ Daniil: dcn32 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 6.1.y. and 6.6.y ]
Signed-off-by: Daniil Dulov <d.dulov@...ddin.ru>
---
Backport fix for CVE-2024-49918
 drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
index 1b1534ffee9f..591c3166a468 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
@@ -2563,8 +2563,10 @@ struct pipe_ctx *dcn32_acquire_idle_pipe_for_head_pipe_in_layer(
 	struct resource_context *old_ctx = &stream->ctx->dc->current_state->res_ctx;
 	int head_index;
 
-	if (!head_pipe)
+	if (!head_pipe) {
 		ASSERT(0);
+		return NULL;
+	}
 
 	/*
 	 * Modified from dcn20_acquire_idle_pipe_for_layer
-- 
2.34.1