[PATCH v2 2/2] driver: uio: fix possible use-after-free in __uio_register_device

[Liu Jian]

In uio_dev_add_attributes() error handing case, idev is used after
device_unregister(), in which 'idev' has been released, touch idev cause
use-after-free.

Fixes: a93e7b331568 ("uio: Prevent device destruction while fds are
open")

Signed-off-by: Liu Jian <liujia...@huawei.com>
Reviewed-by: Hamish Martin <hamish.mar...@alliedtelesis.co.nz>
---
 drivers/uio/uio.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 4d20220..7ee21c8 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -946,6 +946,7 @@ int __uio_register_device(struct module *owner,
                return ret;
        }
 
+       device_initialize(&idev->dev);
        idev->dev.devt = MKDEV(uio_major, idev->minor);
        idev->dev.class = &uio_class;
        idev->dev.parent = parent;
@@ -956,7 +957,7 @@ int __uio_register_device(struct module *owner,
        if (ret)
                goto err_device_create;
 
-       ret = device_register(&idev->dev);
+       ret = device_add(&idev->dev);
        if (ret)
                goto err_device_create;
 
@@ -988,9 +989,10 @@ int __uio_register_device(struct module *owner,
 err_request_irq:
        uio_dev_del_attributes(idev);
 err_uio_dev_add_attributes:
-       device_unregister(&idev->dev);
+       device_del(&idev->dev);
 err_device_create:
        uio_free_minor(idev);
+       put_device(&idev->dev);
        return ret;
 }
 EXPORT_SYMBOL_GPL(__uio_register_device);
-- 
2.7.4