From b507cc9710d8b6e3013468b40522e235342fc84a Mon Sep 17 00:00:00 2001 From: Pete Zaitcev Date: Tue, 4 Mar 2008 23:28:42 -0800 Subject: [PATCH] USB: fix usb-serial generic recursive lock Nobody should be using the generic usb-serial for anything other than testing. Still, it's not a good thing that it's easy to lock up. There is a traceback from NMI oopser here: https://bugzilla.redhat.com/show_bug.cgi?id=431379 But in short, if a line discipline has a chance to echo anything, input can loop back a write method. So, don't call tty_flip_buffer_push from under a lock taken on write path. Signed-off-by: Pete Zaitcev Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/generic.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index 97fa3c4..7cfce9d 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -323,7 +323,7 @@ static void flush_and_resubmit_read_urb (struct usb_serial_port *port) room = tty_buffer_request_room(tty, urb->actual_length); if (room) { tty_insert_flip_string(tty, urb->transfer_buffer, room); - tty_flip_buffer_push(tty); /* is this allowed from an URB callback ? */ + tty_flip_buffer_push(tty); } } @@ -349,10 +349,12 @@ void usb_serial_generic_read_bulk_callback (struct urb *urb) /* Throttle the device if requested by tty */ spin_lock_irqsave(&port->lock, flags); - if (!(port->throttled = port->throttle_req)) - /* Handle data and continue reading from device */ + if (!(port->throttled = port->throttle_req)) { + spin_unlock_irqrestore(&port->lock, flags); flush_and_resubmit_read_urb(port); - spin_unlock_irqrestore(&port->lock, flags); + } else { + spin_unlock_irqrestore(&port->lock, flags); + } } EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback); -- 2.7.4