From 46aaba9641cad198377e8f246da5efb9f8963d8c Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Wed, 22 Jun 2022 10:02:43 +0200
Subject: drm/vc4: perfmon: Fix variable dereferenced before check
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Git-commit: 5f701324c0fb6f9f5aaac3f8d1575321375f6d8f
Patch-mainline: v5.19-rc5
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

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>
Reviewed-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220622080243.22119-1-maxime@cerno.tech
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 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)
-- 
2.38.1