linux-kernel - [ 18/27] USB: OHCI: workaround for hardware bug: retired TDs not added to the Done Queue

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20121214222255.428009233@linuxfoundation.org>
Date:	Fri, 14 Dec 2012 15:01:31 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>
Subject: [ 18/27] USB: OHCI: workaround for hardware bug: retired TDs not added to the Done Queue

3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 50ce5c0683aa83eb161624ea89daa5a9eee0c2ce upstream.

This patch (as1636) is a partial workaround for a hardware bug
affecting OHCI controllers by NVIDIA at least, maybe others too.  When
the controller retires a Transfer Descriptor, it is supposed to add
the TD onto the Done Queue.  But sometimes this doesn't happen, with
the result that ohci-hcd never realizes the corresponding transfer has
finished.  Symptoms can vary; a typical result is that USB audio stops
working after a while.

The patch works around the problem by recognizing that TDs are always
processed in order.  Therefore, if a later TD is found on the Done
Queue than all the earlier TDs for the same endpoint must be finished
as well.

Unfortunately this won't solve the problem in cases where the missing
TD is the last one in the endpoint's queue.  A complete fix would
require a signficant amount of change to the driver.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Tested-by: Oliver Neukum <oneukum@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/ohci-q.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

--- a/drivers/usb/host/ohci-q.c
+++ b/drivers/usb/host/ohci-q.c
@@ -1128,6 +1128,25 @@ dl_done_list (struct ohci_hcd *ohci)

 	while (td) {
 		struct td	*td_next = td->next_dl_td;
+		struct ed	*ed = td->ed;
+
+		/*
+		 * Some OHCI controllers (NVIDIA for sure, maybe others)
+		 * occasionally forget to add TDs to the done queue.  Since
+		 * TDs for a given endpoint are always processed in order,
+		 * if we find a TD on the donelist then all of its
+		 * predecessors must be finished as well.
+		 */
+		for (;;) {
+			struct td	*td2;
+
+			td2 = list_first_entry(&ed->td_list, struct td,
+					td_list);
+			if (td2 == td)
+				break;
+			takeback_td(ohci, td2);
+		}
+
 		takeback_td(ohci, td);
 		td = td_next;
 	}

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/