USB: EHCI: bugfix: urb->hcpriv should not be NULL
authorAlan Stern <stern@rowland.harvard.edu>
Thu, 8 Nov 2012 15:17:01 +0000 (10:17 -0500)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 17 Dec 2012 19:07:43 +0000 (11:07 -0800)
commit2083ca13781c4e88049b530c954dd48b3f30ddf2
tree869d7498dbc404aae3a3b30e9b844ee361533811
parent9eb7f6942b507dc7f94ae380e025cd610d2de269
USB: EHCI: bugfix: urb->hcpriv should not be NULL

commit 2656a9abcf1ec8dd5fee6a75d6997a0f2fa0094e upstream.

This patch (as1632b) fixes a bug in ehci-hcd.  The USB core uses
urb->hcpriv to determine whether or not an URB is active; host
controller drivers are supposed to set this pointer to a non-NULL
value when an URB is queued.  However ehci-hcd sets it to NULL for
isochronous URBs, which defeats the check in usbcore.

In itself this isn't a big deal.  But people have recently found that
certain sequences of actions will cause the snd-usb-audio driver to
reuse URBs without waiting for them to complete.  In the absence of
proper checking by usbcore, the URBs get added to their endpoint list
twice.  This leads to list corruption and a system freeze.

The patch makes ehci-hcd assign a meaningful value to urb->hcpriv for
isochronous URBs.  Improving robustness always helps.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Artem S. Tashkinov <t.artem@lycos.com>
Reported-by: Christof Meerwald <cmeerw@cmeerw.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/host/ehci-q.c
drivers/usb/host/ehci-sched.c