[PATCH] drm/amd/display: Fix dc stream excess put in dm_update_crtc_state()

[Wentao Liang]

In dm_update_crtc_state(), when a modeset is required the newly created
stream is stored in dm_new_crtc_state->stream and an extra reference is
taken with dc_stream_retain().  The reference returned by
create_validate_stream_for_sink() is released as an extra reference at
the skip_modeset label, leaving the stream owned by the new CRTC state.

If amdgpu_dm_check_crtc_color_mgmt() fails afterwards, the code jumps
to the fail label which releases new_stream again.  Since the extra
reference was already released at skip_modeset, this drops the
reference owned by dm_new_crtc_state->stream and the stream is
released while the atomic state still points to it, leading to a
premature free of the dc stream.

Set new_stream to NULL after releasing the extra reference at the
skip_modeset label so that a later goto fail cannot release the
reference owned by the new CRTC state.

Fixes: 7cd4b70091a5 ("drm/amd/display: Rework CRTC color management")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Wentao Liang <vulab@xxxxxxxxxxx>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 5fc5d5608506..28300a3e757a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -11706,8 +11706,10 @@ static int dm_update_crtc_state(struct amdgpu_display_manager *dm,
 
 skip_modeset:
 	/* Release extra reference */
-	if (new_stream)
+	if (new_stream) {
 		dc_stream_release(new_stream);
+		new_stream = NULL;
+	}
 
 	/*
 	 * We want to do dc stream updates that do not require a
-- 
2.34.1