linux-kernel - [PATCH][next] drm/amd/display: don't release dc->current

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Message-Id: <20190629122750.12219-1-colin.king@canonical.com>
Date:   Sat, 29 Jun 2019 13:27:50 +0100
From:   Colin King <colin.king@...onical.com>
To:     Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Zhou <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/amd/display: don't release dc->current_state if it is null

From: Colin Ian King <colin.king@...onical.com>

Currently function construct calls destruct if the allocation of
dc->current_state fails, however, the destruct function will
attempt dereference dc->current_state when calling dc_release_state.
Avoid this null pointer dereference by checking if the pointer is
not null before calling dc_release_state.

Addresses-Coverity: ("Dereference after null check")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 18c775a950cc..0e1f132ae310 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -608,8 +608,10 @@ const struct dc_link_settings *dc_link_get_link_cap(
 
 static void destruct(struct dc *dc)
 {
-	dc_release_state(dc->current_state);
-	dc->current_state = NULL;
+	if (dc->current_state) {
+		dc_release_state(dc->current_state);
+		dc->current_state = NULL;
+	}
 
 	destroy_links(dc);
 
-- 
2.20.1