USB: cdc-acm: fix possible deadlock with multiple openers

The lock must be dropped before usb_autopm_interface_put() is called

Signed-off-by: Oliver Neukum <oliver@neukum.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 5155ff2..b97f930 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -553,7 +553,7 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 
        acm = acm_table[tty->index];
        if (!acm || !acm->dev)
-               goto err_out;
+               goto out;
        else
                rv = 0;
 
@@ -569,8 +569,9 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
 
        mutex_lock(&acm->mutex);
        if (acm->port.count++) {
+               mutex_unlock(&acm->mutex);
                usb_autopm_put_interface(acm->control);
-               goto done;
+               goto out;
        }
 
        acm->ctrlurb->dev = acm->dev;
@@ -599,18 +600,18 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
        set_bit(ASYNCB_INITIALIZED, &acm->port.flags);
        rv = tty_port_block_til_ready(&acm->port, tty, filp);
        tasklet_schedule(&acm->urb_task);
-done:
+
        mutex_unlock(&acm->mutex);
-err_out:
+out:
        mutex_unlock(&open_mutex);
        return rv;
 
 full_bailout:
        usb_kill_urb(acm->ctrlurb);
 bail_out:
-       usb_autopm_put_interface(acm->control);
        acm->port.count--;
        mutex_unlock(&acm->mutex);
+       usb_autopm_put_interface(acm->control);
 early_bail:
        mutex_unlock(&open_mutex);
        tty_port_tty_set(&acm->port, NULL);