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

[Yizhuo Zhai]

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