[PATCH] drm/amdgpu/display: Fix dc_sink refcnt leak in dc_link_detect_helper

[Xiyu Yang]

dc_link_detect_helper() invokes dc_sink_retain(), which increases the
refcount of the "prev_sink".

When dc_link_detect_helper() returns, local variable "prev_sink" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
dc_link_detect_helper(). When alt mode times out, the function forgets
to decrease the refcnt increased by dc_sink_retain(), causing a refcnt
leak.

Fix this issue by calling dc_sink_release() when alt mode times out.

Signed-off-by: Xiyu Yang <xiyuyang19 at fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf at gmail.com>
---
 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 a09119c10d7c..91550d9a1abb 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
@@ -832,6 +832,8 @@ static bool dc_link_detect_helper(struct dc_link *link,
 
 				/* if alt mode times out, return false */
 				if (wait_for_alt_mode(link) == false) {
+					if (prev_sink != NULL)
+						dc_sink_release(prev_sink);
 					return false;
 				}
 			}
-- 
2.7.4