linux-kernel - [PATCH 5.15 494/846] drm/amd/display: check top_pipe_to

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Date:   Mon, 24 Jan 2022 19:40:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Abaci Robot <abaci@...ux.alibaba.com>,
        Yang Li <yang.lee@...ux.alibaba.com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 494/846] 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 c798c65d42765..1860ccc3f4f2c 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -2703,7 +2703,8 @@ 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