Commit aafb00a9 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
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USB: yurex: fix NULL-derefs on disconnect 



The driver was using its struct usb_interface pointer as an inverted
disconnected flag, but was setting it to NULL without making sure all
code paths that used it were done with it.

Before commit ef61eb43 ("USB: yurex: Fix protection fault after
device removal") this included the interrupt-in completion handler, but
there are further accesses in dev_err and dev_dbg statements in
yurex_write() and the driver-data destructor (sic!).

Fix this by unconditionally stopping also the control URB at disconnect
and by using a dedicated disconnected flag.

Note that we need to take a reference to the struct usb_interface to
avoid a use-after-free in the destructor whenever the device was
disconnected while the character device was still open.

Fixes: aadd6472 ("USB: yurex.c: remove dbg() usage")
Fixes: 45714104 ("USB: yurex.c: remove err() usage")
Cc: stable <stable@vger.kernel.org>     # 3.5: ef61eb43
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-6-johan@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ebb2fe57

drivers/usb/misc/yurex.c

+7 −4
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ struct usb_yurex { 


	struct kref		kref;

	struct mutex		io_mutex;

	unsigned long		disconnected:1;

	struct fasync_struct	*async_queue;

	wait_queue_head_t	waitq;
@@ -107,6 +108,7 @@ static void yurex_delete(struct kref *kref) 
				dev->int_buffer, dev->urb->transfer_dma);

		usb_free_urb(dev->urb);

	}

	usb_put_intf(dev->interface);

	usb_put_dev(dev->udev);

	kfree(dev);

}
@@ -205,7 +207,7 @@ static int yurex_probe(struct usb_interface *interface, const struct usb_device_ 
	init_waitqueue_head(&dev->waitq);



	dev->udev = usb_get_dev(interface_to_usbdev(interface));

	dev->interface = interface;

	dev->interface = usb_get_intf(interface);



	/* set up the endpoint information */

	iface_desc = interface->cur_altsetting;
@@ -316,8 +318,9 @@ static void yurex_disconnect(struct usb_interface *interface) 


	/* prevent more I/O from starting */

	usb_poison_urb(dev->urb);

	usb_poison_urb(dev->cntl_urb);

	mutex_lock(&dev->io_mutex);

	dev->interface = NULL;

	dev->disconnected = 1;

	mutex_unlock(&dev->io_mutex);



	/* wakeup waiters */
@@ -405,7 +408,7 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count, 
	dev = file->private_data;



	mutex_lock(&dev->io_mutex);

	if (!dev->interface) {		/* already disconnected */

	if (dev->disconnected) {		/* already disconnected */

		mutex_unlock(&dev->io_mutex);

		return -ENODEV;

	}
@@ -440,7 +443,7 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer, 
		goto error;



	mutex_lock(&dev->io_mutex);

	if (!dev->interface) {		/* already disconnected */

	if (dev->disconnected) {		/* already disconnected */

		mutex_unlock(&dev->io_mutex);

		retval = -ENODEV;

		goto error;

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