On Wed, Oct 19, 2022 at 10:32:14AM +0530, Gautam Menghani wrote:
> 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().
>
> Fixes: 21677cfc562a ("V4L/DVB: ir-core: add imon driver")
> Link: https://syzkaller.appspot.com/bug?id=e378e6a51fbe6c5cc43e34f131cc9a315ef0337e
> Reported-by: syzbot+0c3cb6dc05fbbdc3ad66@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> Signed-off-by: Gautam Menghani <gautammenghani201@xxxxxxxxx>
> ---
> drivers/media/rc/imon.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c
> index 735b925da998..91d8056666ec 100644
> --- a/drivers/media/rc/imon.c
> +++ b/drivers/media/rc/imon.c
> @@ -646,15 +646,14 @@ 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);
> @@ -955,7 +954,8 @@ static ssize_t vfd_write(struct file *file, const char __user *buf,
> if (ictx->disconnected)
> 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");
> --
> 2.34.1
>
Hi,
Please review the above fix and let me know if any changes are required.
Thanks,
Gautam
