[PATCH] drm/amd/display: Fix the uninitialized variable in enable_stream_features()

[Alex Deucher]

Applied.  Thanks!

Alex

On Fri, Dec 17, 2021 at 11:22 PM Yizhuo Zhai <yzhai003 at ucr.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 at vger.kernel.org
> Signed-off-by: Yizhuo Zhai <yzhai003 at ucr.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
>