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    Subject[PATCH 3.10 29/77] USB: usb_wwan: fix write and suspend race
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Johan Hovold <jhovold@gmail.com>

    commit 170fad9e22df0063eba0701adb966786d7a4ec5a upstream.

    Fix race between write() and suspend() which could lead to writes being
    dropped (or I/O while suspended) if the device is runtime suspended
    while a write request is being processed.

    Specifically, suspend() releases the susp_lock after determining the
    device is idle but before setting the suspended flag, thus leaving a
    window where a concurrent write() can submit an urb.

    Fixes: 383cedc3bb43 ("USB: serial: full autosuspend support for the
    option driver")

    Signed-off-by: Johan Hovold <jhovold@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/serial/usb_wwan.c | 13 +++++--------
    1 file changed, 5 insertions(+), 8 deletions(-)

    --- a/drivers/usb/serial/usb_wwan.c
    +++ b/drivers/usb/serial/usb_wwan.c
    @@ -583,20 +583,17 @@ static void stop_read_write_urbs(struct
    int usb_wwan_suspend(struct usb_serial *serial, pm_message_t message)
    {
    struct usb_wwan_intf_private *intfdata = serial->private;
    - int b;

    + spin_lock_irq(&intfdata->susp_lock);
    if (PMSG_IS_AUTO(message)) {
    - spin_lock_irq(&intfdata->susp_lock);
    - b = intfdata->in_flight;
    - spin_unlock_irq(&intfdata->susp_lock);
    -
    - if (b)
    + if (intfdata->in_flight) {
    + spin_unlock_irq(&intfdata->susp_lock);
    return -EBUSY;
    + }
    }
    -
    - spin_lock_irq(&intfdata->susp_lock);
    intfdata->suspended = 1;
    spin_unlock_irq(&intfdata->susp_lock);
    +
    stop_read_write_urbs(serial);

    return 0;



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