linux-kernel - [PATCH] peci: cpu: Fix use-after-free in adev

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Date:   Tue,  5 Jul 2022 12:15:01 +0200
From:   Iwona Winiarska <iwona.winiarska@...el.com>
To:     linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org,
        Jianglei Nie <niejianglei2021@....com>
Cc:     Iwona Winiarska <iwona.winiarska@...el.com>
Subject: [PATCH] peci: cpu: Fix use-after-free in adev_release()

When auxiliary_device_add() returns an error, auxiliary_device_uninit()
is called, which causes refcount for device to be decremented and
.release callback will be triggered.

Because adev_release() re-calls auxiliary_device_uninit(), it will cause
use-after-free:
[ 1269.455172] WARNING: CPU: 0 PID: 14267 at lib/refcount.c:28 refcount_warn_saturate+0x110/0x15
[ 1269.464007] refcount_t: underflow; use-after-free.

Reported-by: Jianglei Nie <niejianglei2021@....com>
Signed-off-by: Iwona Winiarska <iwona.winiarska@...el.com>
---
 drivers/peci/cpu.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/peci/cpu.c b/drivers/peci/cpu.c
index 68eb61c65d34..de4a7b3e5966 100644
--- a/drivers/peci/cpu.c
+++ b/drivers/peci/cpu.c
@@ -188,8 +188,6 @@ static void adev_release(struct device *dev)
 {
 	struct auxiliary_device *adev = to_auxiliary_dev(dev);
 
-	auxiliary_device_uninit(adev);
-
 	kfree(adev->name);
 	kfree(adev);
 }
@@ -234,6 +232,7 @@ static void unregister_adev(void *_adev)
 	struct auxiliary_device *adev = _adev;
 
 	auxiliary_device_delete(adev);
+	auxiliary_device_uninit(adev);
 }
 
 static int devm_adev_add(struct device *dev, int idx)
-- 
2.36.1