linux-kernel - [PATCH] drm/amd/display: Fix the uninitialized variable in enable_stream

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Message-Id: <20211218042226.2608212-1-yzhai003@ucr.edu>
Date:   Fri, 17 Dec 2021 20:22:23 -0800
From:   Yizhuo Zhai <yzhai003@....edu>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Yizhuo Zhai <yzhai003@....edu>, stable@...r.kernel.org,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Wenjing Liu <wenjing.liu@....com>, Jun Lei <jun.lei@....com>,
        Jimmy Kizito <Jimmy.Kizito@....com>,
        Fangzhi Zuo <Jerry.Zuo@....com>,
        Meenakshikumar Somasundaram <meenakshikumar.somasundaram@....com>,
        Mark Morra <MarkAlbert.Morra@....com>,
        Agustin Gutierrez <agustin.gutierrez@....com>,
        Robin Singh <robin.singh@....com>,
        Anthony Koo <Anthony.Koo@....com>,
        "Guo, Bing" <Bing.Guo@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] drm/amd/display: Fix the uninitialized variable in enable_stream_features()

In function enable_stream_features(), the variable "old_downspread.raw"
could be uninitialized if core_link_read_dpcd() fails, however, it is
used in the later if statement, and further, core_link_write_dpcd()
may write random value, which is potentially unsafe.

Fixes: 6016cd9dba0f ("drm/amd/display: add helper for enabling mst stream features")
Cc: stable@...r.kernel.org
Signed-off-by: Yizhuo Zhai <yzhai003@....edu>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
index c8457babfdea..fd5a0e7eb029 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -1844,6 +1844,8 @@ static void enable_stream_features(struct pipe_ctx *pipe_ctx)
 		union down_spread_ctrl old_downspread;
 		union down_spread_ctrl new_downspread;
 
+		memset(&old_downspread, 0, sizeof(old_downspread));
+
 		core_link_read_dpcd(link, DP_DOWNSPREAD_CTRL,
 				&old_downspread.raw, sizeof(old_downspread));
 
-- 
2.25.1