This is a note to let you know that I've just added the patch titled USB: dummy-hcd: Fix deadlock caused by disconnect detection 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: usb-dummy-hcd-fix-deadlock-caused-by-disconnect-detection.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 <stable@xxxxxxxxxxxxxxx> know about it. >From ab219221a5064abfff9f78c323c4a257b16cdb81 Mon Sep 17 00:00:00 2001 From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> Date: Fri, 6 Oct 2017 10:27:44 -0400 Subject: USB: dummy-hcd: Fix deadlock caused by disconnect detection From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 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: [<ffffffffa0547e03>] composite_disconnect+0x43/0x100 [libcomposite] [ 88.365051] [ 88.365051] but task is already holding lock: [ 88.365826] (&(&cdev->lock)->rlock){....}, at: [<ffffffffa0547b09>] 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: [<ffffffffa0547b09>] usb_function_deactivate+0x29/0x80 [libcomposite] [ 88.374814] #1: (&(&dum_hcd->dum->lock)->rlock){....}, at: [<ffffffffa05bd48d>] 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 <stern@xxxxxxxxxxxxxxxxxxx> Reported-by: David Tulloh <david@xxxxxxxxxxxx> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/usb/gadget/udc/dummy_hcd.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/drivers/usb/gadget/udc/dummy_hcd.c +++ b/drivers/usb/gadget/udc/dummy_hcd.c @@ -420,6 +420,7 @@ 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) @@ -430,17 +431,19 @@ 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; /* Currently !connected or in 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) { - unsigned disconnect = USB_PORT_STAT_CONNECTION & + unsigned int disconnect = power_bit & dum_hcd->old_status & (~dum_hcd->port_status); - unsigned reset = USB_PORT_STAT_RESET & + unsigned int reset = USB_PORT_STAT_RESET & (~dum_hcd->old_status) & dum_hcd->port_status; /* Report reset and disconnect events to the driver */ Patches currently in stable-queue which might be from stern@xxxxxxxxxxxxxxxxxxx are queue-4.4/hid-usbhid-fix-out-of-bounds-bug.patch queue-4.4/usb-dummy-hcd-fix-deadlock-caused-by-disconnect-detection.patch