nfc: Fix hangup of RC-S380* in port100_send_ack()

commit 2497128133f8169b24b928852ba6eae34fc495e5 upstream.

If port100_send_ack() was called twice or more, it has race to hangup.

  port100_send_ack()          port100_send_ack()
    init_completion()
    [...]
    dev->cmd_cancel = true
                                /* this removes previous from completion */
                                init_completion()
				[...]
                                dev->cmd_cancel = true
                                wait_for_completion()
    /* never be waked up */
    wait_for_completion()

Like above race, this code is not assuming port100_send_ack() is
called twice or more.

To fix, this checks dev->cmd_cancel to know if prior cancel is
in-flight or not. And never be remove prior task from completion by
using reinit_completion(), so this guarantees to be waked up properly
soon or later.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/nfc/port100.c b/drivers/nfc/port100.c
index 2b2330b..073e4a4 100644 (file)
--- a/drivers/nfc/port100.c
+++ b/drivers/nfc/port100.c
@@ -725,23 +725,33 @@ static int port100_submit_urb_for_ack(struct port100 *dev, gfp_t flags)
 
 static int port100_send_ack(struct port100 *dev)
 {
-       int rc;
+       int rc = 0;
 
        mutex_lock(&dev->out_urb_lock);
 
-       init_completion(&dev->cmd_cancel_done);
+       /*
+        * If prior cancel is in-flight (dev->cmd_cancel == true), we
+        * can skip to send cancel. Then this will wait the prior
+        * cancel, or merged into the next cancel rarely if next
+        * cancel was started before waiting done. In any case, this
+        * will be waked up soon or later.
+        */
+       if (!dev->cmd_cancel) {
+               reinit_completion(&dev->cmd_cancel_done);
 
-       usb_kill_urb(dev->out_urb);
+               usb_kill_urb(dev->out_urb);
 
-       dev->out_urb->transfer_buffer = ack_frame;
-       dev->out_urb->transfer_buffer_length = sizeof(ack_frame);
-       rc = usb_submit_urb(dev->out_urb, GFP_KERNEL);
+               dev->out_urb->transfer_buffer = ack_frame;
+               dev->out_urb->transfer_buffer_length = sizeof(ack_frame);
+               rc = usb_submit_urb(dev->out_urb, GFP_KERNEL);
 
-       /* Set the cmd_cancel flag only if the URB has been successfully
-        * submitted. It will be reset by the out URB completion callback
-        * port100_send_complete().
-        */
-       dev->cmd_cancel = !rc;
+               /*
+                * Set the cmd_cancel flag only if the URB has been
+                * successfully submitted. It will be reset by the out
+                * URB completion callback port100_send_complete().
+                */
+               dev->cmd_cancel = !rc;
+       }
 
        mutex_unlock(&dev->out_urb_lock);
 
@@ -928,8 +938,8 @@ static void port100_send_complete(struct urb *urb)
        struct port100 *dev = urb->context;
 
        if (dev->cmd_cancel) {
+               complete_all(&dev->cmd_cancel_done);
                dev->cmd_cancel = false;
-               complete(&dev->cmd_cancel_done);
        }
 
        switch (urb->status) {
@@ -1543,6 +1553,7 @@ static int port100_probe(struct usb_interface *interface,
                            PORT100_COMM_RF_HEAD_MAX_LEN;
        dev->skb_tailroom = PORT100_FRAME_TAIL_LEN;
 
+       init_completion(&dev->cmd_cancel_done);
        INIT_WORK(&dev->cmd_complete_work, port100_wq_cmd_complete);
 
        /* The first thing to do with the Port-100 is to set the command type