patch "USB: OHCI: Fix race between ED unlink and URB submission" added to usb-linus

[<gregkh@linuxfoundation.org>]

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

    USB: OHCI: Fix race between ED unlink and URB submission

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 7d8021c967648accd1b78e5e1ddaad655cd2c61f Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@rowland.harvard.edu>
Date: Tue, 30 Jun 2015 11:25:54 -0400
Subject: USB: OHCI: Fix race between ED unlink and URB submission

This patch fixes a bug introduced by commit 977dcfdc6031 ("USB: OHCI:
don't lose track of EDs when a controller dies").  The commit changed
ed_state from ED_UNLINK to ED_IDLE too early, before finish_urb() had
been called.  The user-visible consequence is that the driver
occasionally crashes or locks up when an URB is submitted while
another URB for the same endpoint is being unlinked.

This patch moves the ED state change later, to the right place.  The
drawback is that now we may unnecessarily execute some instructions
multiple times when a controller dies.  Since controllers dying is an
exceptional occurrence, a little wasted time won't matter.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Heiko Przybyl <lil_tux@web.de>
Tested-by: Heiko Przybyl <lil_tux@web.de>
Fixes: 977dcfdc60311e7aa571cabf6f39c36dde13339e
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/usb/host/ohci-q.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
index f7d561ed3c23..d029bbe9eb36 100644
--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -981,10 +981,6 @@ rescan_all:
 		int			completed, modified;
 		__hc32			*prev;
 
-		/* Is this ED already invisible to the hardware? */
-		if (ed->state == ED_IDLE)
-			goto ed_idle;
-
 		/* only take off EDs that the HC isn't using, accounting for
 		 * frame counter wraps and EDs with partially retired TDs
 		 */
@@ -1012,12 +1008,10 @@ skip_ed:
 		}
 
 		/* ED's now officially unlinked, hc doesn't see */
-		ed->state = ED_IDLE;
 		ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
 		ed->hwNextED = 0;
 		wmb();
 		ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE);
-ed_idle:
 
 		/* reentrancy:  if we drop the schedule lock, someone might
 		 * have modified this list.  normally it's just prepending
@@ -1088,6 +1082,7 @@ rescan_this:
 		if (list_empty(&ed->td_list)) {
 			*last = ed->ed_next;
 			ed->ed_next = NULL;
+			ed->state = ED_IDLE;
 			list_del(&ed->in_use_list);
 		} else if (ohci->rh_state == OHCI_RH_RUNNING) {
 			*last = ed->ed_next;
-- 
2.4.6