USB: usbserial - fix potential deadlock between write() and IRQ

patch acd2a847e7fee7df11817f67dba75a2802793e5d in mainline.

USB: usbserial - fix potential deadlock between write() and IRQ

usb_serial_generic_write() doesn't disable interrupts when taking port->lock,
and could therefore deadlock with usb_serial_generic_read_bulk_callback()
being called from interrupt, taking the same lock. Fix it.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Larry Finger <larry.finger@lwfinger.net>
Cc: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
index 88a2c7dce335f9b1cde151ae457bf1d55054132d..9eb4a65ee4d9943026f74de49c4e3013c8f3f65f 100644 (file)
--- a/drivers/usb/serial/generic.c
+++ b/drivers/usb/serial/generic.c
@@ -208,14 +208,15 @@ int usb_serial_generic_write(struct usb_serial_port *port, const unsigned char *
 
        /* only do something if we have a bulk out endpoint */
        if (serial->num_bulk_out) {
-               spin_lock_bh(&port->lock);
+               unsigned long flags;
+               spin_lock_irqsave(&port->lock, flags);
                if (port->write_urb_busy) {
-                       spin_unlock_bh(&port->lock);
+                       spin_unlock_irqrestore(&port->lock, flags);
                        dbg("%s - already writing", __FUNCTION__);
                        return 0;
                }
                port->write_urb_busy = 1;
-               spin_unlock_bh(&port->lock);
+               spin_unlock_irqrestore(&port->lock, flags);
 
                count = (count > port->bulk_out_size) ? port->bulk_out_size : count;