linux-kernel - [PATCH AUTOSEL 5.16 060/217] drm/amd/display: check top_pipe_to

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Date:   Mon, 17 Jan 2022 21:17:03 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Yang Li <yang.lee@...ux.alibaba.com>,
        Abaci Robot <abaci@...ux.alibaba.com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, harry.wentland@....com,
        sunpeng.li@....com, Rodrigo.Siqueira@....com,
        christian.koenig@....com, Xinhui.Pan@....com, airlied@...ux.ie,
        daniel@...ll.ch, nathan@...nel.org, ndesaulniers@...gle.com,
        nicholas.kazlauskas@....com, Anson.Jacob@....com, aric.cyr@....com,
        Wayne.Lin@....com, meenakshikumar.somasundaram@....com,
        michael.strauss@....com, haonan.wang2@....com,
        Martin.Leung@....com, Jimmy.Kizito@....com, Eric.Yang2@....com,
        lee.jones@...aro.org, Lewis.Huang@....com, roy.chan@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        llvm@...ts.linux.dev
Subject: [PATCH AUTOSEL 5.16 060/217] drm/amd/display: check top_pipe_to_program pointer

From: Yang Li <yang.lee@...ux.alibaba.com>

[ Upstream commit a689e8d1f80012f90384ebac9dcfac4201f9f77e ]

Clang static analysis reports this error

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc.c:2870:7: warning:
Dereference of null pointer [clang-analyzer-core.NullDereference]
                if
(top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
                    ^

top_pipe_to_program being NULL is caught as an error
But then it is used to report the error.

So add a check before using it.

Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 0ded4decee05f..f0fbd8ad56229 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2870,7 +2870,8 @@ static void commit_planes_for_stream(struct dc *dc,
 #endif
 
 	if ((update_type != UPDATE_TYPE_FAST) && stream->update_flags.bits.dsc_changed)
-		if (top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
+		if (top_pipe_to_program &&
+			top_pipe_to_program->stream_res.tg->funcs->lock_doublebuffer_enable) {
 			if (should_use_dmub_lock(stream->link)) {
 				union dmub_hw_lock_flags hw_locks = { 0 };
 				struct dmub_hw_lock_inst_flags inst_flags = { 0 };
-- 
2.34.1