linux-kernel - [PATCH RFC 1/6] drm/msm: fix null pointer dereference in msm_atomic_prepare

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Message-Id: <20190505130413.32253-2-masneyb@onstation.org>
Date:   Sun,  5 May 2019 09:04:08 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     robdclark@...il.com, sean@...rly.run,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, airlied@...ux.ie, daniel@...ll.ch,
        linux-kernel@...r.kernel.org, linus.walleij@...aro.org
Subject: [PATCH RFC 1/6] drm/msm: fix null pointer dereference in msm_atomic_prepare_fb()

_msm_gem_new() calls msm_gem_new_impl() with a NULL reservation_object
struct. msm_atomic_prepare_fb() assumes that the reservation_object is
always set, and attempts to reference a NULL pointer. Correct this by
checking to see if this value is NULL.

Signed-off-by: Brian Masney <masneyb@...tation.org>
---
 drivers/gpu/drm/msm/msm_atomic.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
index f5b1256e32b6..0da80a93876a 100644
--- a/drivers/gpu/drm/msm/msm_atomic.c
+++ b/drivers/gpu/drm/msm/msm_atomic.c
@@ -56,10 +56,12 @@ int msm_atomic_prepare_fb(struct drm_plane *plane,
 		return 0;
 
 	obj = msm_framebuffer_bo(new_state->fb, 0);
-	msm_obj = to_msm_bo(obj);
-	fence = reservation_object_get_excl_rcu(msm_obj->resv);
 
-	drm_atomic_set_fence_for_plane(new_state, fence);
+	msm_obj = to_msm_bo(obj);
+	if (msm_obj->resv) {
+		fence = reservation_object_get_excl_rcu(msm_obj->resv);
+		drm_atomic_set_fence_for_plane(new_state, fence);
+	}
 
 	return msm_framebuffer_prepare(new_state->fb, kms->aspace);
 }
-- 
2.20.1