From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932140AbdL1Rwo (ORCPT ); Thu, 28 Dec 2017 12:52:44 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:58868 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754317AbdL1RN6 (ORCPT ); Thu, 28 Dec 2017 12:13:58 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Alan Stern" , "Felipe Balbi" , "David Tulloh" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 101/204] USB: dummy-hcd: Fix deadlock caused by disconnect detection In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Alan Stern commit ab219221a5064abfff9f78c323c4a257b16cdb81 upstream. The dummy-hcd driver calls the gadget driver's disconnect callback under the wrong conditions. It should invoke the callback when Vbus power is turned off, but instead it does so when the D+ pullup is turned off. This can cause a deadlock in the composite core when a gadget driver is unregistered: [ 88.361471] ============================================ [ 88.362014] WARNING: possible recursive locking detected [ 88.362580] 4.14.0-rc2+ #9 Not tainted [ 88.363010] -------------------------------------------- [ 88.363561] v4l_id/526 is trying to acquire lock: [ 88.364062] (&(&cdev->lock)->rlock){....}, at: [] composite_disconnect+0x43/0x100 [libcomposite] [ 88.365051] [ 88.365051] but task is already holding lock: [ 88.365826] (&(&cdev->lock)->rlock){....}, at: [] usb_function_deactivate+0x29/0x80 [libcomposite] [ 88.366858] [ 88.366858] other info that might help us debug this: [ 88.368301] Possible unsafe locking scenario: [ 88.368301] [ 88.369304] CPU0 [ 88.369701] ---- [ 88.370101] lock(&(&cdev->lock)->rlock); [ 88.370623] lock(&(&cdev->lock)->rlock); [ 88.371145] [ 88.371145] *** DEADLOCK *** [ 88.371145] [ 88.372211] May be due to missing lock nesting notation [ 88.372211] [ 88.373191] 2 locks held by v4l_id/526: [ 88.373715] #0: (&(&cdev->lock)->rlock){....}, at: [] usb_function_deactivate+0x29/0x80 [libcomposite] [ 88.374814] #1: (&(&dum_hcd->dum->lock)->rlock){....}, at: [] dummy_pullup+0x7d/0xf0 [dummy_hcd] [ 88.376289] [ 88.376289] stack backtrace: [ 88.377726] CPU: 0 PID: 526 Comm: v4l_id Not tainted 4.14.0-rc2+ #9 [ 88.378557] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 [ 88.379504] Call Trace: [ 88.380019] dump_stack+0x86/0xc7 [ 88.380605] __lock_acquire+0x841/0x1120 [ 88.381252] lock_acquire+0xd5/0x1c0 [ 88.381865] ? composite_disconnect+0x43/0x100 [libcomposite] [ 88.382668] _raw_spin_lock_irqsave+0x40/0x54 [ 88.383357] ? composite_disconnect+0x43/0x100 [libcomposite] [ 88.384290] composite_disconnect+0x43/0x100 [libcomposite] [ 88.385490] set_link_state+0x2d4/0x3c0 [dummy_hcd] [ 88.386436] dummy_pullup+0xa7/0xf0 [dummy_hcd] [ 88.387195] usb_gadget_disconnect+0xd8/0x160 [udc_core] [ 88.387990] usb_gadget_deactivate+0xd3/0x160 [udc_core] [ 88.388793] usb_function_deactivate+0x64/0x80 [libcomposite] [ 88.389628] uvc_function_disconnect+0x1e/0x40 [usb_f_uvc] This patch changes the code to test the port-power status bit rather than the port-connect status bit when deciding whether to isue the callback. Signed-off-by: Alan Stern Reported-by: David Tulloh Signed-off-by: Felipe Balbi [bwh: Backported to 3.16: adjust filename, context] Signed-off-by: Ben Hutchings --- --- a/drivers/usb/gadget/dummy_hcd.c +++ b/drivers/usb/gadget/dummy_hcd.c @@ -355,6 +355,7 @@ static void set_link_state_by_speed(stru static void set_link_state(struct dummy_hcd *dum_hcd) { struct dummy *dum = dum_hcd->dum; + unsigned int power_bit; dum_hcd->active = 0; if (dum->pullup) @@ -365,19 +366,21 @@ static void set_link_state(struct dummy_ return; set_link_state_by_speed(dum_hcd); + power_bit = (dummy_hcd_to_hcd(dum_hcd)->speed == HCD_USB3 ? + USB_SS_PORT_STAT_POWER : USB_PORT_STAT_POWER); if ((dum_hcd->port_status & USB_PORT_STAT_ENABLE) == 0 || dum_hcd->active) dum_hcd->resuming = 0; /* if !connected or reset */ - if ((dum_hcd->port_status & USB_PORT_STAT_CONNECTION) == 0 || + if ((dum_hcd->port_status & power_bit) == 0 || (dum_hcd->port_status & USB_PORT_STAT_RESET) != 0) { /* * We're connected and not reset (reset occurred now), * and driver attached - disconnect! */ - if ((dum_hcd->old_status & USB_PORT_STAT_CONNECTION) != 0 && + if ((dum_hcd->old_status & power_bit) != 0 && (dum_hcd->old_status & USB_PORT_STAT_RESET) == 0 && dum->ints_enabled) { stop_activity(dum);