Patch "USB: gadgetfs: fix copy_to_user while holding spinlock" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

USB: gadgetfs: fix copy_to_user while holding spinlock

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-gadgetfs-fix-copy_to_user-while-holding-spinlock.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Alan Stern <[email protected]>
Date: Thu, 21 Sep 2017 16:12:01 -0400
Subject: USB: gadgetfs: fix copy_to_user while holding spinlock

From: Alan Stern <[email protected]>

commit 6e76c01e71551cb221c1f3deacb9dcd9a7346784 upstream.

The gadgetfs driver as a long-outstanding FIXME, regarding a call of copy_to_user() made while holding a spinlock. This patch fixes the issue by dropping the spinlock and using the dev->udc_usage mechanism introduced by another recent patch to guard against status changes while the lock isn't held.

---
 drivers/usb/gadget/legacy/inode.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

@@ -1067,11 +1067,14 @@ ep0_read (struct file *fd, char __user *
 				retval = -EIO;
 			else {
 				len = min (len, (size_t)dev->req->actual);
-// FIXME don't call this with the spinlock held ...
+				++dev->udc_usage;
+				spin_unlock_irq(&dev->lock);
 				if (copy_to_user (buf, dev->req->buf, len))
 					retval = -EFAULT;
 				else
 					retval = len;
+				spin_lock_irq(&dev->lock);
+				--dev->udc_usage;
 				clean_req (dev->gadget->ep0, dev->req);
 				/* NOTE userspace can't yet choose to stall */
 			}

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/usb-dummy-hcd-fix-infinite-loop-resubmission-bug.patch queue-3.18/usb-storage-unusual_devs-entry-to-fix-write-access-regression-for-seagate-external-drives.patch queue-3.18/usb-gadgetfs-fix-copy_to_user-while-holding-spinlock.patch queue-3.18/usb-devio-don-t-corrupt-user-memory.patch queue-3.18/usb-gadgetfs-fix-crash-caused-by-inadequate-synchronization.patch queue-3.18/usb-dummy-hcd-fix-connection-failures-wrong-speed.patch