Commit 5afeb104 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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USB: usblcd doesn't limit memory consumption during write 



usblcd currently has no way to limit memory consumption by fast writers.
This is a security problem, as it allows users with write access to this
device to drive the system into oom despite resource limits.
Here's the fix taken from the modern skeleton driver.

Signed-off-by: default avatarOliver Neukum <oneukum@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent fc0f8fc9

drivers/usb/misc/usblcd.c

+18 −4
Original line number Diff line number Diff line
@@ -43,9 +43,13 @@ struct usb_lcd { 
	__u8			bulk_in_endpointAddr;	/* the address of the bulk in endpoint */

	__u8			bulk_out_endpointAddr;	/* the address of the bulk out endpoint */

	struct kref		kref;

	struct semaphore	limit_sem;		/* to stop writes at full throttle from

							 * using up all RAM */

};

#define to_lcd_dev(d) container_of(d, struct usb_lcd, kref)



#define USB_LCD_CONCURRENT_WRITES	5



static struct usb_driver lcd_driver;

static DEFINE_MUTEX(usb_lcd_open_mutex);
@@ -186,12 +190,13 @@ static void lcd_write_bulk_callback(struct urb *urb) 
	/* free up our allocated buffer */

	usb_buffer_free(urb->dev, urb->transfer_buffer_length,

			urb->transfer_buffer, urb->transfer_dma);

	up(&dev->limit_sem);

}



static ssize_t lcd_write(struct file *file, const char __user * user_buffer, size_t count, loff_t *ppos)

{

	struct usb_lcd *dev;

        int retval = 0;

        int retval = 0, r;

	struct urb *urb = NULL;

	char *buf = NULL;
@@ -201,10 +206,16 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, siz 
	if (count == 0)

		goto exit;



	r = down_interruptible(&dev->limit_sem);

	if (r < 0)

		return -EINTR;



	/* create a urb, and a buffer for it, and copy the data to the urb */

	urb = usb_alloc_urb(0, GFP_KERNEL);

	if (!urb)

		return -ENOMEM;

	if (!urb) {

		retval = -ENOMEM;

		goto err_no_buf;

	}

	

	buf = usb_buffer_alloc(dev->udev, count, GFP_KERNEL, &urb->transfer_dma);

	if (!buf) {
@@ -239,6 +250,8 @@ exit: 
error:

	usb_buffer_free(dev->udev, count, buf, urb->transfer_dma);

	usb_free_urb(urb);

err_no_buf:

	up(&dev->limit_sem);

	return retval;

}
@@ -277,6 +290,7 @@ static int lcd_probe(struct usb_interface *interface, const struct usb_device_id 
		goto error;

	}

	kref_init(&dev->kref);

	sema_init(&dev->limit_sem, USB_LCD_CONCURRENT_WRITES);



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

	dev->interface = interface;

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