[PATCH] drm/vc4: perfmon: Fix variable dereferenced before check

From: Maxime Ripard <maxime@cerno.tech>
To: dri-devel@lists.freedesktop.org
Cc: kernel test robot <lkp@intel.com>,
	David Airlie <airlied@linux.ie>,
	Maxime Ripard <maxime@cerno.tech>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	Daniel Vetter <daniel.vetter@intel.com>,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: [PATCH] drm/vc4: perfmon: Fix variable dereferenced before check
Date: Wed, 22 Jun 2022 10:02:43 +0200	[thread overview]
Message-ID: <20220622080243.22119-1-maxime@cerno.tech> (raw)

Commit 30f8c74ca9b7 ("drm/vc4: Warn if some v3d code is run on BCM2711")
introduced a check in vc4_perfmon_get() that dereferences a pointer before
we checked whether that pointer is valid or not.

Let's rework that function a bit to do things in the proper order.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 30f8c74ca9b7 ("drm/vc4: Warn if some v3d code is run on BCM2711")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_perfmon.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_perfmon.c b/drivers/gpu/drm/vc4/vc4_perfmon.c
index c7f5adb6bcf8..79a74184d732 100644
--- a/drivers/gpu/drm/vc4/vc4_perfmon.c
+++ b/drivers/gpu/drm/vc4/vc4_perfmon.c
@@ -17,13 +17,16 @@
 
 void vc4_perfmon_get(struct vc4_perfmon *perfmon)
 {
-	struct vc4_dev *vc4 = perfmon->dev;
+	struct vc4_dev *vc4;
 
+	if (!perfmon)
+		return;
+
+	vc4 = perfmon->dev;
 	if (WARN_ON_ONCE(vc4->is_vc5))
 		return;
 
-	if (perfmon)
-		refcount_inc(&perfmon->refcnt);
+	refcount_inc(&perfmon->refcnt);
 }
 
 void vc4_perfmon_put(struct vc4_perfmon *perfmon)
-- 
2.36.1

