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Commit e93da893 authored by Guanghui Feng's avatar Guanghui Feng Committed by Greg Kroah-Hartman
Browse files

uio: Fix use-after-free in uio_open 



commit 0c9ae0b8605078eafc3bea053cc78791e97ba2e2 upstream.

core-1				core-2
-------------------------------------------------------
uio_unregister_device		uio_open
				idev = idr_find()
device_unregister(&idev->dev)
put_device(&idev->dev)
uio_device_release
				get_device(&idev->dev)
kfree(idev)
uio_free_minor(minor)
				uio_release
				put_device(&idev->dev)
				kfree(idev)
-------------------------------------------------------

In the core-1 uio_unregister_device(), the device_unregister will kfree
idev when the idev->dev kobject ref is 1. But after core-1
device_unregister, put_device and before doing kfree, the core-2 may
get_device. Then:
1. After core-1 kfree idev, the core-2 will do use-after-free for idev.
2. When core-2 do uio_release and put_device, the idev will be double
   freed.

To address this issue, we can get idev atomic & inc idev reference with
minor_lock.

Fixes: 57c5f4df ("uio: fix crash after the device is unregistered")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarGuanghui Feng <guanghuifeng@linux.alibaba.com>
Reviewed-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/1703152663-59949-1-git-send-email-guanghuifeng@linux.alibaba.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent da488e1a

drivers/uio/uio.c

+3 −4
Original line number Diff line number Diff line
@@ -464,13 +464,13 @@ static int uio_open(struct inode *inode, struct file *filep) 


	mutex_lock(&minor_lock);

	idev = idr_find(&uio_idr, iminor(inode));

	mutex_unlock(&minor_lock);

	if (!idev) {

		ret = -ENODEV;

		mutex_unlock(&minor_lock);

		goto out;

	}



	get_device(&idev->dev);

	mutex_unlock(&minor_lock);



	if (!try_module_get(idev->owner)) {

		ret = -ENODEV;
@@ -1024,9 +1024,8 @@ void uio_unregister_device(struct uio_info *info) 
	wake_up_interruptible(&idev->wait);

	kill_fasync(&idev->async_queue, SIGIO, POLL_HUP);



	device_unregister(&idev->dev);



	uio_free_minor(minor);

	device_unregister(&idev->dev);



	return;

}