USB: cdc-acm: fix potential urb leak and PM imbalance in write

Make sure to check return value of autopm get in write() in order to
avoid urb leak and PM counter imbalance on errors.

Fixes: 11ea859d64b6 ("USB: additional power savings for cdc-acm devices
that support remote wakeup")

Cc: <stable@vger.kernel.org>	# v2.6.27
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 1ac6c5dda9f7..c255e77282ad 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -668,7 +668,13 @@ static int acm_tty_write(struct tty_struct *tty,
         memcpy(wb->buf, buf, count);
         wb->len = count;
 
-        usb_autopm_get_interface_async(acm->control);
+        stat = usb_autopm_get_interface_async(acm->control);
+        if (stat) {
+                wb->use = 0;
+                spin_unlock_irqrestore(&acm->write_lock, flags);
+                return stat;
+        }
+
         if (acm->susp_count) {
                 usb_anchor_urb(wb->urb, &acm->delayed);
                 spin_unlock_irqrestore(&acm->write_lock, flags);