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

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Date:   Tue, 10 Aug 2021 02:20:04 -0700
From:   Tuo Li <islituo@...il.com>
To:     harry.wentland@....com, sunpeng.li@....com,
        alexander.deucher@....com, christian.koenig@....com,
        Xinhui.Pan@....com, airlied@...ux.ie, daniel@...ll.ch,
        aric.cyr@....com, Jun.Lei@....com, qingqing.zhuo@....com,
        Rodrigo.Siqueira@....com, alvin.lee2@....com,
        vladimir.stempen@....com, isabel.zhang@....com, sung.lee@....com,
        paul.hsieh@....com, wyatt.wood@....com
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, baijiaju1990@...il.com,
        Tuo Li <islituo@...il.com>, TOTE Robot <oslab@...nghua.edu.cn>
Subject: [PATCH] drm/display: fix possible null-pointer dereference in dcn10_set_clock()

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 possible null-pointer dereference, check dc->clk_mgr before
dereferencing it.

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
Signed-off-by: Tuo Li <islituo@...il.com>
---
 drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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 c545eddabdcc..3a7c7c7efa68 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
@@ -3635,7 +3635,7 @@ enum dc_status dcn10_set_clock(struct dc *dc,
 				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;
 
 	if (clk_khz > clock_cfg.max_clock_khz)
-- 
2.25.1