From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759405Ab2I1Ujq (ORCPT ); Fri, 28 Sep 2012 16:39:46 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:40590 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758894Ab2I1Ujo (ORCPT ); Fri, 28 Sep 2012 16:39:44 -0400 X-Sasl-enc: wpKuxLiJhrpAyVs/FqAMDdu8tN7tuiatAbXvSK8mSwYj 1348864783 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Alan Stern , Don Zickus Subject: [ 212/218] USB: Fix race condition when removing host controllers Date: Fri, 28 Sep 2012 13:17:09 -0700 Message-Id: <20120928201525.927855802@linuxfoundation.org> X-Mailer: git-send-email 1.7.12.1.428.g652398a In-Reply-To: <20120928201501.208384923@linuxfoundation.org> References: <20120928201501.208384923@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alan Stern commit 0d00dc2611abbe6ad244d50569c2ee82ce42846c upstream. This patch (as1607) fixes a race that can occur if a USB host controller is removed while a process is reading the /sys/kernel/debug/usb/devices file. The usb_device_read() routine uses the bus->root_hub pointer to determine whether or not the root hub is registered. The is not a valid test, because the pointer is set before the root hub gets registered and remains set even after the root hub is unregistered and deallocated. As a result, usb_device_read() or usb_device_dump() can access freed memory, causing an oops. The patch changes the test to use the hcd->rh_registered flag, which does get set and cleared at the appropriate times. It also makes sure to hold the usb_bus_list_lock mutex while setting the flag, so that usb_device_read() will become aware of new root hubs as soon as they are registered. Signed-off-by: Alan Stern Reported-by: Don Zickus Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devices.c | 2 +- drivers/usb/core/hcd.c | 6 ++---- 2 files changed, 3 insertions(+), 5 deletions(-) --- a/drivers/usb/core/devices.c +++ b/drivers/usb/core/devices.c @@ -624,7 +624,7 @@ static ssize_t usb_device_read(struct fi /* print devices for all busses */ list_for_each_entry(bus, &usb_bus_list, bus_list) { /* recurse through all children of the root hub */ - if (!bus->root_hub) + if (!bus_to_hcd(bus)->rh_registered) continue; usb_lock_device(bus->root_hub); ret = usb_device_dump(&buf, &nbytes, &skip_bytes, ppos, --- a/drivers/usb/core/hcd.c +++ b/drivers/usb/core/hcd.c @@ -1002,10 +1002,7 @@ static int register_root_hub(struct usb_ if (retval) { dev_err (parent_dev, "can't register root hub for %s, %d\n", dev_name(&usb_dev->dev), retval); - } - mutex_unlock(&usb_bus_list_lock); - - if (retval == 0) { + } else { spin_lock_irq (&hcd_root_hub_lock); hcd->rh_registered = 1; spin_unlock_irq (&hcd_root_hub_lock); @@ -1014,6 +1011,7 @@ static int register_root_hub(struct usb_ if (HCD_DEAD(hcd)) usb_hc_died (hcd); /* This time clean up */ } + mutex_unlock(&usb_bus_list_lock); return retval; }