Patch "USB: gadgetfs: fix copy_to_user while holding spinlock" has been added to the 4.13-stable tree

[<gregkh@linuxfoundation.org>]

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 4.13-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-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6e76c01e71551cb221c1f3deacb9dcd9a7346784 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Thu, 21 Sep 2017 16:12:01 -0400
Subject: USB: gadgetfs: fix copy_to_user while holding spinlock

From: Alan Stern <stern@rowland.harvard.edu>

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.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -986,11 +986,14 @@ 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 stern@rowland.harvard.edu are

queue-4.13/usb-storage-fix-bogus-hardware-error-messages-for-ata-pass-thru-devices.patch
queue-4.13/usb-devio-prevent-integer-overflow-in-proc_do_submiturb.patch
queue-4.13/usb-dummy-hcd-fix-infinite-loop-resubmission-bug.patch
queue-4.13/usb-storage-unusual_devs-entry-to-fix-write-access-regression-for-seagate-external-drives.patch
queue-4.13/usb-gadgetfs-fix-copy_to_user-while-holding-spinlock.patch
queue-4.13/usb-devio-don-t-corrupt-user-memory.patch
queue-4.13/usb-gadgetfs-fix-crash-caused-by-inadequate-synchronization.patch
queue-4.13/usb-dummy-hcd-fix-connection-failures-wrong-speed.patch
queue-4.13/usb-dummy-hcd-fix-erroneous-synchronization-change.patch