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

From: Xiyu Yang
Date: Thu Apr 23 2020 - 01:05:26 EST


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@xxxxxxxxxxxx>
Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
---
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