USB: usbcore: Introduce usb_bulk_msg_killable()

The synchronous message API in usbcore (usb_control_msg(),
usb_bulk_msg(), and so on) uses uninterruptible waits.  However,
drivers may call these routines in the context of a user thread, which
means it ought to be possible to at least kill them.

For this reason, introduce a new usb_bulk_msg_killable() function
which behaves the same as usb_bulk_msg() except for using
wait_for_completion_killable_timeout() instead of
wait_for_completion_timeout().  The same can be done later for
usb_control_msg() later on, if it turns out to be needed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Suggested-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/linux-usb/3acfe838-6334-4f6d-be7c-4bb01704b33d@rowland.harvard.edu/
Fixes: 1da177e ("Linux-2.6.12-rc2")
CC: stable@vger.kernel.org
Link: https://patch.msgid.link/248628b4-cc83-4e81-a620-3ce4e0376d41@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: AlanStern

drivers/usb/core/message.c

@@ -42,16 +42,17 @@ static void usb_api_blocking_completion(struct urb *urb)
 
 
 /*
- * Starts urb and waits for completion or timeout. Note that this call
- * is NOT interruptible. Many device driver i/o requests should be
- * interruptible and therefore these drivers should implement their
- * own interruptible routines.
+ * Starts urb and waits for completion or timeout.
+ * Whether or not the wait is killable depends on the flag passed in.
+ * For example, compare usb_bulk_msg() and usb_bulk_msg_killable().
  */
-static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
+static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length,
+		bool killable)
 {
 	struct api_context ctx;
 	unsigned long expire;
 	int retval;
+	long rc;
 
 	init_completion(&ctx.done);
 	urb->context = &ctx;
@@ -61,12 +62,21 @@ static int usb_start_wait_urb(struct urb *urb, int timeout, int *actual_length)
 		goto out;
 
 	expire = timeout ? msecs_to_jiffies(timeout) : MAX_SCHEDULE_TIMEOUT;
-	if (!wait_for_completion_timeout(&ctx.done, expire)) {
+	if (killable)
+		rc = wait_for_completion_killable_timeout(&ctx.done, expire);
+	else
+		rc = wait_for_completion_timeout(&ctx.done, expire);
+	if (rc <= 0) {
 		usb_kill_urb(urb);
-		retval = (ctx.status == -ENOENT ? -ETIMEDOUT : ctx.status);
+		if (ctx.status != -ENOENT)
+			retval = ctx.status;
+		else if (rc == 0)
+			retval = -ETIMEDOUT;
+		else
+			retval = rc;
 
 		dev_dbg(&urb->dev->dev,
-			"%s timed out on ep%d%s len=%u/%u\n",
+			"%s timed out or killed on ep%d%s len=%u/%u\n",
 			current->comm,
 			usb_endpoint_num(&urb->ep->desc),
 			usb_urb_dir_in(urb) ? "in" : "out",
@@ -100,7 +110,7 @@ static int usb_internal_control_msg(struct usb_device *usb_dev,
 	usb_fill_control_urb(urb, usb_dev, pipe, (unsigned char *)cmd, data,
 			     len, usb_api_blocking_completion, NULL);
 
-	retv = usb_start_wait_urb(urb, timeout, &length);
+	retv = usb_start_wait_urb(urb, timeout, &length, false);
 	if (retv < 0)
 		return retv;
 	else
@@ -385,10 +395,59 @@ int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe,
 		usb_fill_bulk_urb(urb, usb_dev, pipe, data, len,
 				usb_api_blocking_completion, NULL);
 
-	return usb_start_wait_urb(urb, timeout, actual_length);
+	return usb_start_wait_urb(urb, timeout, actual_length, false);
 }
 EXPORT_SYMBOL_GPL(usb_bulk_msg);
 
+/**
+ * usb_bulk_msg_killable - Builds a bulk urb, sends it off and waits for completion in a killable state
+ * @usb_dev: pointer to the usb device to send the message to
+ * @pipe: endpoint "pipe" to send the message to
+ * @data: pointer to the data to send
+ * @len: length in bytes of the data to send
+ * @actual_length: pointer to a location to put the actual length transferred
+ *	in bytes
+ * @timeout: time in msecs to wait for the message to complete before
+ *	timing out (if 0 the wait is forever)
+ *
+ * Context: task context, might sleep.
+ *
+ * This function is just like usb_blk_msg() except that it waits in a
+ * killable state.
+ *
+ * Return:
+ * If successful, 0. Otherwise a negative error number. The number of actual
+ * bytes transferred will be stored in the @actual_length parameter.
+ *
+ */
+int usb_bulk_msg_killable(struct usb_device *usb_dev, unsigned int pipe,
+		 void *data, int len, int *actual_length, int timeout)
+{
+	struct urb *urb;
+	struct usb_host_endpoint *ep;
+
+	ep = usb_pipe_endpoint(usb_dev, pipe);
+	if (!ep || len < 0)
+		return -EINVAL;
+
+	urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!urb)
+		return -ENOMEM;
+
+	if ((ep->desc.bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) ==
+			USB_ENDPOINT_XFER_INT) {
+		pipe = (pipe & ~(3 << 30)) | (PIPE_INTERRUPT << 30);
+		usb_fill_int_urb(urb, usb_dev, pipe, data, len,
+				usb_api_blocking_completion, NULL,
+				ep->desc.bInterval);
+	} else
+		usb_fill_bulk_urb(urb, usb_dev, pipe, data, len,
+				usb_api_blocking_completion, NULL);
+
+	return usb_start_wait_urb(urb, timeout, actual_length, true);
+}
+EXPORT_SYMBOL_GPL(usb_bulk_msg_killable);
+
 /*-------------------------------------------------------------------*/
 
 static void sg_clean(struct usb_sg_request *io)

include/linux/usb.h

@@ -1868,8 +1868,9 @@ extern int usb_control_msg(struct usb_device *dev, unsigned int pipe,
 extern int usb_interrupt_msg(struct usb_device *usb_dev, unsigned int pipe,
 	void *data, int len, int *actual_length, int timeout);
 extern int usb_bulk_msg(struct usb_device *usb_dev, unsigned int pipe,
-	void *data, int len, int *actual_length,
-	int timeout);
+	void *data, int len, int *actual_length, int timeout);
+extern int usb_bulk_msg_killable(struct usb_device *usb_dev, unsigned int pipe,
+	void *data, int len, int *actual_length, int timeout);
 
 /* wrappers around usb_control_msg() for the most common standard requests */
 int usb_control_msg_send(struct usb_device *dev, __u8 endpoint, __u8 request,