Re: [PATCH V1 1/3] rpmsg: glink: Free device context only when cdev not in use

Mathieu Poirier
2022-02-03T17:35:18Z

Hi Deepak,

On Thu, Jan 27, 2022 at 12:34:44AM +0530, Deepak Kumar Singh wrote:
> Struct device holding cdev should not be freed unless cdev
> is not in use. It is possible that user space has opened
> char device while kernel has freed the associated struct
> device context.
>
> Mark dev kobj as parent of cdev, so that chardev_add gets
> an extra reference to dev. This ensures device context is not
> freed until cdev is is not in uses.
> ---
> drivers/rpmsg/rpmsg_char.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
> index c03a118..72ee101 100644
> --- a/drivers/rpmsg/rpmsg_char.c
> +++ b/drivers/rpmsg/rpmsg_char.c
> @@ -417,6 +417,7 @@ static int rpmsg_eptdev_create(struct rpmsg_ctrldev *ctrldev,
> dev->id = ret;
> dev_set_name(dev, "rpmsg%d", ret);
>
> + cdev_set_parent(&eptdev->cdev, &dev->kobj);
> ret = cdev_add(&eptdev->cdev, dev->devt, 1);

This issue should have been fixed when cdev_add() was replaced by
cdev_device_add(), something you will find on v5.17-rc2.

Also, this set is generating checkpatch warnings and as such I will not review
the other patches in it.

Thanks,
Mathieu

> if (ret)
> goto free_ept_ida;
> @@ -533,6 +534,7 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
> dev->id = ret;
> dev_set_name(&ctrldev->dev, "rpmsg_ctrl%d", ret);
>
> + cdev_set_parent(&ctrldev->cdev, &dev->kobj);
> ret = cdev_add(&ctrldev->cdev, dev->devt, 1);
> if (ret)
> goto free_ctrl_ida;
> --
> 2.7.4
>