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From:   Min Li <lm0963hack@gmail.com>
To:     jani.nikula@linux.intel.com
Cc:     joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com,
        tvrtko.ursulin@linux.intel.com, airlied@gmail.com, daniel@ffwll.ch,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/1] drm/i915: fix race condition UAF in i915_perf_add_config_ioctl
Date:   Tue, 28 Mar 2023 17:36:27 +0800
Message-Id: <20230328093627.5067-1-lm0963hack@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Userspace can guess the id value and try to race oa_config object creation
with config remove, resulting in a use-after-free if we dereference the
object after unlocking the metrics_lock.  For that reason, unlocking the
metrics_lock must be done after we are done dereferencing the object.

Signed-off-by: Min Li <lm0963hack@gmail.com>
---
 drivers/gpu/drm/i915/i915_perf.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 824a34ec0b83..93748ca2c5da 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -4634,13 +4634,13 @@ int i915_perf_add_config_ioctl(struct drm_device *dev, void *data,
 		err = oa_config->id;
 		goto sysfs_err;
 	}
-
-	mutex_unlock(&perf->metrics_lock);
+	id = oa_config->id;
 
 	drm_dbg(&perf->i915->drm,
 		"Added config %s id=%i\n", oa_config->uuid, oa_config->id);
+	mutex_unlock(&perf->metrics_lock);
 
-	return oa_config->id;
+	return id;
 
 sysfs_err:
 	mutex_unlock(&perf->metrics_lock);
-- 
2.25.1