linux-kernel - [PATCH] drm/amd/display: Fix potential NULL pointer dereferences in amdgpu_dm_atomic_commit

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Date:   Mon, 27 Nov 2017 08:57:00 -0600
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH] drm/amd/display: Fix potential NULL pointer dereferences in
 amdgpu_dm_atomic_commit_tail

dm_new_crtc_state->stream and disconnected_acrtc are being dereferenced
before they are null checked, hence there is a potential null pointer
dereference.

Fix this by null checking such pointers before they are dereferenced.

Addresses-Coverity-ID: 1423745 ("Dereference before null check")
Addresses-Coverity-ID: 1423833 ("Dereference before null check")
Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_types and amdgpu_dm")
Fixes: 54d765752467 ("drm/amd/display: Unify amdgpu_dm state variable namings.")
Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

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 889ed24..3bdd137 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4190,6 +4190,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 
 		dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
 
+		if (!dm_new_crtc_state->stream)
+			continue;
+
 		update_stream_scaling_settings(&dm_new_con_state->base.crtc->mode,
 				dm_new_con_state, (struct dc_stream_state *)dm_new_crtc_state->stream);
 
@@ -4197,9 +4200,6 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 		WARN_ON(!status);
 		WARN_ON(!status->plane_count);
 
-		if (!dm_new_crtc_state->stream)
-			continue;
-
 		/*TODO How it works with MPO ?*/
 		if (!dc_commit_planes_to_stream(
 				dm->dc,
@@ -4332,9 +4332,11 @@ void dm_restore_drm_connector_state(struct drm_device *dev,
 		return;
 
 	disconnected_acrtc = to_amdgpu_crtc(connector->encoder->crtc);
-	acrtc_state = to_dm_crtc_state(disconnected_acrtc->base.state);
+	if (!disconnected_acrtc)
+		return;
 
-	if (!disconnected_acrtc || !acrtc_state->stream)
+	acrtc_state = to_dm_crtc_state(disconnected_acrtc->base.state);
+	if (!acrtc_state->stream)
 		return;
 
 	/*
-- 
2.7.4