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USB: fix usb-serial generic recursive lock

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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 <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Pete Zaitcev 2008-03-04 23:28:42 -08:00 committed by Greg Kroah-Hartman
parent cdeeeae056
commit b507cc9710
1 changed files with 6 additions and 4 deletions
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10
drivers/usb/serial/generic.c
View file

@ -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);