[PATCH] USB: OHCI: Don't mark EDs as ED_OPER if scheduling fails

[PATCH] USB: OHCI: Don't mark EDs as ED_OPER if scheduling fails

[Michał Pecio]

commit c66f59ee5050447b3da92d36f5385a847990a894 upstream.

Since ed_schedule begins with marking the ED as "operational",
the ED may be left in such state even if scheduling actually
fails.

This allows future submission attempts to smuggle this ED to the
hardware behind the scheduler's back and without linking it to
the ohci->eds_in_use list.

The former causes bandwidth saturation and data loss on isoc
endpoints, the latter crashes the kernel when attempt is made
to unlink such ED from this list.

Fix ed_schedule to update ED state only on successful return.

Signed-off-by: Michal Pecio <michal.pecio@gmail.com>
---

Hi,

This commit had been submitted to 4.7 without cc:stable because
it wasn't decided at the time whether we want this fix in stable.

It turned out we want it in 3.18 and later so I'm sending it here.

Regards,
MP



 drivers/usb/host/ohci-q.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c
index d029bbe..641fed6 100644
--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -183,7 +183,6 @@ static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
 {
 	int	branch;
 
-	ed->state = ED_OPER;
 	ed->ed_prev = NULL;
 	ed->ed_next = NULL;
 	ed->hwNextED = 0;
@@ -259,6 +258,8 @@ static int ed_schedule (struct ohci_hcd *ohci, struct ed *ed)
 	/* the HC may not see the schedule updates yet, but if it does
 	 * then they'll be properly ordered.
 	 */
+
+	ed->state = ED_OPER;
 	return 0;
 }
 
-- 
2.8.3