linux-kernel - [PATCH] i915-pmu: Add extra check engine

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Message-Id: <20220816123858.42489-1-arefev@swemel.ru>
Date:   Tue, 16 Aug 2022 15:38:57 +0300
From:   Denis Arefev <arefev@...mel.ru>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: [PATCH] i915-pmu: Add extra check engine

Return value of a function 'intel_engine_lookup_user' is dereferenced at i915_pmu.c:708
without checking for null, but it is usually checked for this function

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Denis Arefev <arefev@...mel.ru>
---
 drivers/gpu/drm/i915/i915_pmu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 69c0fa20eba1..33db49ffac3d 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -704,8 +704,10 @@ static void i915_pmu_disable(struct perf_event *event)
 		 * Decrement the reference count and clear the enabled
 		 * bitmask when the last listener on an event goes away.
 		 */
-		if (--engine->pmu.enable_count[sample] == 0)
-			engine->pmu.enable &= ~BIT(sample);
+		if (engine != NULL) {
+		        if (--engine->pmu.enable_count[sample] == 0)
+			        engine->pmu.enable &= ~BIT(sample);
+		}
 	}
 
 	GEM_BUG_ON(bit >= ARRAY_SIZE(pmu->enable_count));
-- 
2.25.1