Commit fdd64df7 authored Jan 17, 2020 by Alan Stern Committed by Greg Kroah-Hartman Jan 17, 2020

USB: usbfs: Always unlink URBs in reverse order

When the kernel unlinks a bunch of URBs for a single endpoint, it
should always unlink them in reverse order. This eliminates any
possibility that some URB x will be unlinked before it can execute but
the following URB x+1 will execute before it can be unlinked. Such an
event would be bad, for obvious reasons.

Chris Dickens pointed out that usbfs doesn't behave this way when it
is unbound from an interface. All pending URBs are cancelled, but in
the order of submission. This patch changes the behavior to make the
unlinks occur in reverse order. It similarly changes the behavior
when usbfs cancels the continuation URBs for a BULK endpoint.

Suggested-by: Chris Dickens <christopher.a.dickens@gmail.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.2001171045380.1571-100000@iolanthe.rowland.org

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 50f737ab

drivers/usb/core/devio.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -574,7 +574,7 @@ __acquires(ps->lock)

		/* Now carefully unlink all the marked pending URBs */
		rescan:
		list_for_each_entry(as, &ps->async_pending, asynclist) {
		list_for_each_entry_reverse(as, &ps->async_pending, asynclist) {
		if (as->bulk_status == AS_UNLINK) {
		as->bulk_status = 0; /* Only once */
		urb = as->urb;
		@@ -636,7 +636,7 @@ static void destroy_async(struct usb_dev_state ps, struct list_head list)

		spin_lock_irqsave(&ps->lock, flags);
		while (!list_empty(list)) {
		as = list_entry(list->next, struct async, asynclist);
		as = list_last_entry(list, struct async, asynclist);
		list_del_init(&as->asynclist);
		urb = as->urb;
		usb_get_urb(urb);

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