Commit efe36820 authored Dec 02, 2020 by Sriharsha Allenki Committed by Greg Kroah-Hartman Jan 12, 2021

usb: gadget: Fix spinlock lockup on usb_function_deactivate



commit 5cc35c224a80aa5a5a539510ef049faf0d6ed181 upstream.

There is a spinlock lockup as part of composite_disconnect
when it tries to acquire cdev->lock as part of usb_gadget_deactivate.
This is because the usb_gadget_deactivate is called from
usb_function_deactivate with the same spinlock held.

This would result in the below call stack and leads to stall.

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu:     3-...0: (1 GPs behind) idle=162/1/0x4000000000000000
softirq=10819/10819 fqs=2356
 (detected by 2, t=5252 jiffies, g=20129, q=3770)
 Task dump for CPU 3:
 task:uvc-gadget_wlhe state:R  running task     stack:    0 pid:  674 ppid:
 636 flags:0x00000202
 Call trace:
  __switch_to+0xc0/0x170
  _raw_spin_lock_irqsave+0x84/0xb0
  composite_disconnect+0x28/0x78
  configfs_composite_disconnect+0x68/0x70
  usb_gadget_disconnect+0x10c/0x128
  usb_gadget_deactivate+0xd4/0x108
  usb_function_deactivate+0x6c/0x80
  uvc_function_disconnect+0x20/0x58
  uvc_v4l2_release+0x30/0x88
  v4l2_release+0xbc/0xf0
  __fput+0x7c/0x230
  ____fput+0x14/0x20
  task_work_run+0x88/0x140
  do_notify_resume+0x240/0x6f0
  work_pending+0x8/0x200

Fix this by doing an unlock on cdev->lock before the usb_gadget_deactivate
call from usb_function_deactivate.

The same lockup can happen in the usb_gadget_activate path. Fix that path
as well.

Reported-by: Peter Chen <peter.chen@nxp.com>
Link: https://lore.kernel.org/linux-usb/20201102094936.GA29581@b29397-desktop/


Tested-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201202130220.24926-1-sallenki@codeaurora.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 55dfcc21

drivers/usb/gadget/composite.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -293,8 +293,11 @@ int usb_function_deactivate(struct usb_function *function)

		spin_lock_irqsave(&cdev->lock, flags);

		if (cdev->deactivations == 0)
		if (cdev->deactivations == 0) {
		spin_unlock_irqrestore(&cdev->lock, flags);
		status = usb_gadget_deactivate(cdev->gadget);
		spin_lock_irqsave(&cdev->lock, flags);
		}
		if (status == 0)
		cdev->deactivations++;

		@@ -325,8 +328,11 @@ int usb_function_activate(struct usb_function *function)
		status = -EINVAL;
		else {
		cdev->deactivations--;
		if (cdev->deactivations == 0)
		if (cdev->deactivations == 0) {
		spin_unlock_irqrestore(&cdev->lock, flags);
		status = usb_gadget_activate(cdev->gadget);
		spin_lock_irqsave(&cdev->lock, flags);
		}
		}

		spin_unlock_irqrestore(&cdev->lock, flags);