From: Prashanth K quic_prashk@quicinc.com
[ Upstream commit e5990469943c711cb00bfde6338d2add6c6d0bfe ]
When serial console over USB is enabled, gs_console_connect queues gs_console_work, where it acquires the spinlock and queues the usb request, and this request goes to gadget layer. Now consider a situation where gadget layer prints something to dmesg, this will eventually call gs_console_write() which requires cons->lock. And this causes spinlock recursion. Avoid this by excluding usb_ep_queue from the spinlock.
spin_lock_irqsave //needs cons->lock gs_console_write . . _printk __warn_printk dev_warn/pr_err . . [USB Gadget Layer] . . usb_ep_queue gs_console_work __gs_console_push // acquires cons->lock process_one_work
Signed-off-by: Prashanth K quic_prashk@quicinc.com Link: https://lore.kernel.org/r/1683638872-6885-1-git-send-email-quic_prashk@quici... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/usb/gadget/function/u_serial.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index a0ca47fbff0fc..1bc96ff954ffe 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -916,8 +916,11 @@ static void __gs_console_push(struct gs_console *cons) }
req->length = size; + + spin_unlock_irq(&cons->lock); if (usb_ep_queue(ep, req, GFP_ATOMIC)) req->length = 0; + spin_lock_irq(&cons->lock); }
static void gs_console_work(struct work_struct *work)