Patch "xhci: Fix NULL pointer dereference when cleaning up streams for removed host" has been added to the 4.4-stable tree

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

xhci: Fix NULL pointer dereference when cleaning up streams for removed host

to the 4.4-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:
xhci-fix-null-pointer-dereference-when-cleaning-up-streams-for-removed-host.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mathias Nyman <[email protected]>
Date: Thu, 20 Jul 2017 14:48:26 +0300
Subject: xhci: Fix NULL pointer dereference when cleaning up streams for removed host

From: Mathias Nyman <[email protected]>

commit 4b895868bb2da60a386a17cde3bf9ecbc70c79f4 upstream.

This off by one in stream_id indexing caused NULL pointer dereference and soft lockup on machines with USB attached SCSI devices connected to a hotpluggable xhci controller.

The code that cleans up pending URBs for dead hosts tried to dereference a stream ring at the invalid stream_id 0. ep->stream_info->stream_rings[0] doesn't point to a ring.

Start looping stream_id from 1 like in all the other places in the driver, and check that the ring exists before trying to kill URBs on it.

---
 drivers/usb/host/xhci-ring.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

@@ -856,13 +856,16 @@ static void xhci_kill_endpoint_urbs(stru
 			(ep->ep_state & EP_GETTING_NO_STREAMS)) {
 		int stream_id;
 
-		for (stream_id = 0; stream_id < ep->stream_info->num_streams;
+		for (stream_id = 1; stream_id < ep->stream_info->num_streams;
 				stream_id++) {
+			ring = ep->stream_info->stream_rings[stream_id];
+			if (!ring)
+				continue;
+
 			xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 					"Killing URBs for slot ID %u, ep index %u, stream %u",
-					slot_id, ep_index, stream_id + 1);
-			xhci_kill_ring_urbs(xhci,
-					ep->stream_info->stream_rings[stream_id]);
+					slot_id, ep_index, stream_id);
+			xhci_kill_ring_urbs(xhci, ring);
 		}
 	} else {
 		ring = ep->ring;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/xhci-fix-null-pointer-dereference-when-cleaning-up-streams-for-removed-host.patch queue-4.4/xhci-fix-20000ms-port-resume-timeout.patch