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path: root/drivers/usb/misc/usblcd.c
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Diffstat (limited to 'drivers/usb/misc/usblcd.c')
-rw-r--r--drivers/usb/misc/usblcd.c22
1 files 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 @@ 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;