linux-kernel - [PATCH] dmaengine: idxd: Avoid unnecessary destruction of file

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Date: Mon, 29 Jan 2024 17:39:54 -0800
From: Fenghua Yu <fenghua.yu@...el.com>
To: "Vinod Koul" <vkoul@...nel.org>,
	"Dave Jiang" <dave.jiang@...el.com>
Cc: dmaengine@...r.kernel.org,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Lijun Pan <lijun.pan@...el.com>
Subject: [PATCH] dmaengine: idxd: Avoid unnecessary destruction of file_ida

file_ida is allocated during cdev open and is freed accordingly
during cdev release. This sequence is guaranteed by driver file
operations. Therefore, there is no need to destroy an already empty
file_ida when the WQ cdev is removed.

Worse, ida_free() in cdev release may happen after destruction of 
file_ida per WQ cdev. This can lead to accessing an id in file_ida
after it has been destroyed, resulting in a kernel panic.

Remove ida_destroy(&file_ida) to address these issues.

Fixes: e6fd6d7e5f0f ("dmaengine: idxd: add a device to represent the file opened")
Signed-off-by: Lijun Pan <lijun.pan@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 drivers/dma/idxd/cdev.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
index baa51927675c..3311c920f47a 100644
--- a/drivers/dma/idxd/cdev.c
+++ b/drivers/dma/idxd/cdev.c
@@ -1272,7 +1272,6 @@ void idxd_wq_del_cdev(struct idxd_wq *wq)
 	struct idxd_cdev *idxd_cdev;

 	idxd_cdev = wq->idxd_cdev;
-	ida_destroy(&file_ida);
 	wq->idxd_cdev = NULL;
 	cdev_device_del(&idxd_cdev->cdev, cdev_dev(idxd_cdev));
 	put_device(cdev_dev(idxd_cdev));
-- 
2.37.1