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

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Date:   Wed, 22 Dec 2021 09:36:02 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Yizhuo Zhai <yzhai003@....edu>
Cc:     David Airlie <airlied@...ux.ie>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Meenakshikumar Somasundaram <meenakshikumar.somasundaram@....com>,
        Jun Lei <jun.lei@....com>, Anthony Koo <Anthony.Koo@....com>,
        Jimmy Kizito <Jimmy.Kizito@....com>,
        Wenjing Liu <wenjing.liu@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Fangzhi Zuo <Jerry.Zuo@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        "Guo, Bing" <Bing.Guo@....com>, Leo Li <sunpeng.li@....com>,
        Agustin Gutierrez <agustin.gutierrez@....com>,
        Mark Morra <MarkAlbert.Morra@....com>,
        Robin Singh <robin.singh@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        "for 3.8" <stable@...r.kernel.org>,
        Christian König <christian.koenig@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Subject: Re: [PATCH] drm/amd/display: Fix the uninitialized variable in enable_stream_features()

Applied.  Thanks!

Alex

On Fri, Dec 17, 2021 at 11:22 PM Yizhuo Zhai <yzhai003@....edu> wrote:
>
> 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
>