From 5afeb104e7901168b21aad0437fb51dc620dfdd3 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Mon, 11 Jun 2007 15:36:02 +0200 Subject: [PATCH] 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: Oliver Neukum Signed-off-by: Greg Kroah-Hartman --- drivers/usb/misc/usblcd.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c index 887ef953f3d8..12bad8a205a7 100644 --- a/drivers/usb/misc/usblcd.c +++ b/drivers/usb/misc/usblcd.c @@ -42,10 +42,14 @@ struct usb_lcd { size_t bulk_in_size; /* the size of the receive buffer */ __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 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 @@ static ssize_t lcd_write(struct file *file, const char __user * user_buffer, siz 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;