linux-kernel - [PATCH] drivers: visorbus: fix use-after free bugs

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Date:   Fri, 20 Nov 2020 15:48:44 +0800
From:   Qinglang Miao <miaoqinglang@...wei.com>
To:     David Kershner <david.kershner@...sys.com>,
        <sparmaintainer@...sys.com>
CC:     <linux-kernel@...r.kernel.org>,
        Qinglang Miao <miaoqinglang@...wei.com>
Subject: [PATCH] drivers: visorbus: fix use-after free bugs

kfree(dev) is called in put_device(&dev->device) so that following
use would cause use-after-free bug.

There are two inappropriate use of put_device:

1. In create_visor_device, put dev_err before put_device to fix this.

2. In remove_visor_device, the former put_device is redundant because
   device_unregister contains put_device already.

Fixes: 93d3ad90c2d4 ("drivers: visorbus: move driver out of staging")
Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com>
---
 drivers/visorbus/visorbus_main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/visorbus/visorbus_main.c b/drivers/visorbus/visorbus_main.c
index 152fd29f0..031349baf 100644
--- a/drivers/visorbus/visorbus_main.c
+++ b/drivers/visorbus/visorbus_main.c
@@ -695,15 +695,14 @@ int create_visor_device(struct visor_device *dev)
 	return 0;
 
 err_put:
-	put_device(&dev->device);
 	dev_err(&dev->device, "Creating visor device failed. %d\n", err);
+	put_device(&dev->device);
 	return err;
 }
 
 void remove_visor_device(struct visor_device *dev)
 {
 	list_del(&dev->list_all);
-	put_device(&dev->device);
 	if (dev->pending_msg_hdr)
 		visorbus_response(dev, 0, CONTROLVM_DEVICE_DESTROY);
 	device_unregister(&dev->device);
-- 
2.23.0