[PATCH 4.9 36/45] usb: gadget: Fix spinlock lockup on usb_function_deactivate

Greg Kroah-Hartman
2021-01-11T13:04:49Z

From: Sriharsha Allenki <sallenki@codeaurora.org>

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>

---
drivers/usb/gadget/composite.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -392,8 +392,11 @@ int usb_function_deactivate(struct usb_f

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++;

@@ -424,8 +427,11 @@ int usb_function_activate(struct usb_fun
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);