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    Subject[PATCH 5.16 0861/1039] drm/amd/display: Fix the uninitialized variable in enable_stream_features()
    Date
    From: Yizhuo Zhai <yzhai003@ucr.edu>

    commit 0726ed3065eeb910f9cea0c933bc021a848e00b3 upstream.

    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@vger.kernel.org
    Signed-off-by: Yizhuo Zhai <yzhai003@ucr.edu>
    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/gpu/drm/amd/display/dc/core/dc_link.c | 2 ++
    1 file changed, 2 insertions(+)

    --- 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(struc
    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));


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