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    Subject[patch 24/40] USB: usbserial - fix potential deadlock between write() and IRQ

    -stable review patch. If anyone has any objections, please let us know.

    ------------------
    From: Jiri Kosina <jkosina@suse.cz>

    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>

    ---
    drivers/usb/serial/generic.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    --- a/drivers/usb/serial/generic.c
    +++ b/drivers/usb/serial/generic.c
    @@ -208,14 +208,15 @@ int usb_serial_generic_write(struct usb_

    /* 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;

    --
    -
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