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Commit 1d8521e1 authored by Gautam Menghani's avatar Gautam Menghani Committed by Greg Kroah-Hartman
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media: imon: fix a race condition in send_packet() 

[ Upstream commit 813ceef062b53d68f296aa3cb944b21a091fabdb ]

The function send_packet() has a race condition as follows:

func send_packet()
{
    // do work
    call usb_submit_urb()
    mutex_unlock()
    wait_for_event_interruptible()  <-- lock gone
    mutex_lock()
}

func vfd_write()
{
    mutex_lock()
    call send_packet()  <- prev call is not completed
    mutex_unlock()
}

When the mutex is unlocked and the function send_packet() waits for the
call to complete, vfd_write() can start another call, which leads to the
"URB submitted while active" warning in usb_submit_urb().
Fix this by removing the mutex_unlock() call in send_packet() and using
mutex_lock_interruptible().

Link: https://syzkaller.appspot.com/bug?id=e378e6a51fbe6c5cc43e34f131cc9a315ef0337e



Fixes: 21677cfc ("V4L/DVB: ir-core: add imon driver")
Reported-by: default avatar <syzbot+0c3cb6dc05fbbdc3ad66@syzkaller.appspotmail.com>
Signed-off-by: default avatarGautam Menghani <gautammenghani201@gmail.com>
Signed-off-by: default avatarSean Young <sean@mess.org>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent cf9c4c25

drivers/media/rc/imon.c

+3 −3
Original line number Diff line number Diff line
@@ -604,15 +604,14 @@ static int send_packet(struct imon_context *ictx) 
		pr_err_ratelimited("error submitting urb(%d)\n", retval);

	} else {

		/* Wait for transmission to complete (or abort) */

		mutex_unlock(&ictx->lock);

		retval = wait_for_completion_interruptible(

				&ictx->tx.finished);

		if (retval) {

			usb_kill_urb(ictx->tx_urb);

			pr_err_ratelimited("task interrupted\n");

		}

		mutex_lock(&ictx->lock);



		ictx->tx.busy = false;

		retval = ictx->tx.status;

		if (retval)

			pr_err_ratelimited("packet tx failed (%d)\n", retval);
@@ -919,7 +918,8 @@ static ssize_t vfd_write(struct file *file, const char __user *buf, 
		return -ENODEV;

	}



	mutex_lock(&ictx->lock);

	if (mutex_lock_interruptible(&ictx->lock))

		return -ERESTARTSYS;



	if (!ictx->dev_present_intf0) {

		pr_err_ratelimited("no iMON device present\n");