linux-kernel - [PATCH 5.4 131/260] drm/display: fix possible null-pointer dereference in dcn10_set

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Message-Id: <20210920163935.582450275@linuxfoundation.org>
Date:   Mon, 20 Sep 2021 18:42:29 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, TOTE Robot <oslab@...nghua.edu.cn>,
        Tuo Li <islituo@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 131/260] drm/display: fix possible null-pointer dereference in dcn10_set_clock()

From: Tuo Li <islituo@...il.com>

[ Upstream commit 554594567b1fa3da74f88ec7b2dc83d000c58e98 ]

The variable dc->clk_mgr is checked in:
  if (dc->clk_mgr && dc->clk_mgr->funcs->get_clock)

This indicates dc->clk_mgr can be NULL.
However, it is dereferenced in:
    if (!dc->clk_mgr->funcs->get_clock)

To fix this null-pointer dereference, check dc->clk_mgr and the function
pointer dc->clk_mgr->funcs->get_clock earlier, and return if one of them
is NULL.

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
Signed-off-by: Tuo Li <islituo@...il.com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
index 60123db7ba02..bc5ebea1abed 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c
@@ -3264,13 +3264,12 @@ static enum dc_status dcn10_set_clock(struct dc *dc,
 	struct dc_clock_config clock_cfg = {0};
 	struct dc_clocks *current_clocks = &context->bw_ctx.bw.dcn.clk;
 
-	if (dc->clk_mgr && dc->clk_mgr->funcs->get_clock)
-				dc->clk_mgr->funcs->get_clock(dc->clk_mgr,
-						context, clock_type, &clock_cfg);
-
-	if (!dc->clk_mgr->funcs->get_clock)
+	if (!dc->clk_mgr || !dc->clk_mgr->funcs->get_clock)
 		return DC_FAIL_UNSUPPORTED_1;
 
+	dc->clk_mgr->funcs->get_clock(dc->clk_mgr,
+		context, clock_type, &clock_cfg);
+
 	if (clk_khz > clock_cfg.max_clock_khz)
 		return DC_FAIL_CLK_EXCEED_MAX;
 
@@ -3288,7 +3287,7 @@ static enum dc_status dcn10_set_clock(struct dc *dc,
 	else
 		return DC_ERROR_UNEXPECTED;
 
-	if (dc->clk_mgr && dc->clk_mgr->funcs->update_clocks)
+	if (dc->clk_mgr->funcs->update_clocks)
 				dc->clk_mgr->funcs->update_clocks(dc->clk_mgr,
 				context, true);
 	return DC_OK;
-- 
2.30.2