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Commit 24971281 authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Samuel Ortiz
Browse files

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



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: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarSamuel Ortiz <sameo@linux.intel.com>
parent 0ada0768

drivers/nfc/port100.c

+23 −12
Original line number Diff line number Diff line
@@ -726,11 +726,19 @@ 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);
@@ -738,11 +746,13 @@ static int port100_send_ack(struct port100 *dev) 
		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().

		/*

		 * 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);
@@ -929,8 +939,8 @@ 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) {
@@ -1546,6 +1556,7 @@ 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