On Fri, Jun 04, 2021 at 11:14:05AM +0200, Arnaud Pouliquen wrote:
> Using the RPMSG_RELEASE_DEV_IOCTL is possible to remove any
> rpmsg device (such as the rpmsg ns or the rpmsg ctrldev).
>
> Add a new field to store the removability of the device.
>
> By default the rpmsg device can not be removed by user space. It is
> set to 1 by the rpmsg ctrl on RPMSG_CREATE_DEV_IOCTL request, but
> could also be set by an rpmsg driver during probe.
>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
> ---
> drivers/rpmsg/rpmsg_ctrl.c | 17 ++++++++++++++++-
> include/linux/rpmsg.h | 2 ++
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/rpmsg/rpmsg_ctrl.c b/drivers/rpmsg/rpmsg_ctrl.c
> index cb19e32d05e1..e93c6ec49038 100644
> --- a/drivers/rpmsg/rpmsg_ctrl.c
> +++ b/drivers/rpmsg/rpmsg_ctrl.c
> @@ -74,6 +74,7 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd,
> struct rpmsg_endpoint_info eptinfo;
> struct rpmsg_channel_info chinfo;
> struct rpmsg_device *rpdev;
> + struct device *dev;
> int ret = 0;
>
> if (copy_from_user(&eptinfo, argp, sizeof(eptinfo)))
> @@ -95,11 +96,25 @@ static long rpmsg_ctrldev_ioctl(struct file *fp, unsigned int cmd,
> if (!rpdev) {
> dev_err(&ctrldev->dev, "failed to create %s channel\n", chinfo.name);
> ret = -ENXIO;
> + } else {
> + /* Allow user space to release the device. */
> + rpdev->us_removable = 1;
As a rule of thumb I try really hard to avoid introducing new flags. In this case we
can attain the same result by looking at chinfo->name, chinfo->src and
chinfo->dst. I would introduce a new inline function in rpmsg_internal.h,
something like rpmsg_chrdev_is_ctrl_dev(), and compare the specifics in chinfo
to rpdev->id.name, rpdev->src and rpdev->dst. If they all match then the
operation is refused.
That way we don't introduce a new flag and there is also no need to call
rpmsg_find_device() twice.
Thanks,
Mathieu
> }
> break;
>
> case RPMSG_RELEASE_DEV_IOCTL:
> - ret = rpmsg_release_channel(ctrldev->rpdev, &chinfo);
> + dev = rpmsg_find_device(ctrldev->rpdev->dev.parent, &chinfo);
> + if (!dev)
> + ret = -ENXIO;
> +
> + /* Verify that rpmsg device removal is allowed. */
> + if (!ret) {
> + rpdev = to_rpmsg_device(dev);
> + if (!rpdev->us_removable)
> + ret = -EACCES;
> + }
> + if (!ret)
> + ret = rpmsg_release_channel(ctrldev->rpdev, &chinfo);
> if (ret)
> dev_err(&ctrldev->dev, "failed to release %s channel (%d)\n",
> chinfo.name, ret);
> diff --git a/include/linux/rpmsg.h b/include/linux/rpmsg.h
> index d97dcd049f18..3642aad1a789 100644
> --- a/include/linux/rpmsg.h
> +++ b/include/linux/rpmsg.h
> @@ -47,6 +47,7 @@ struct rpmsg_channel_info {
> * @ept: the rpmsg endpoint of this channel
> * @announce: if set, rpmsg will announce the creation/removal of this channel
> * @little_endian: True if transport is using little endian byte representation
> + * @us_removable: True if userspace application has permission to remove the rpmsg device
> */
> struct rpmsg_device {
> struct device dev;
> @@ -57,6 +58,7 @@ struct rpmsg_device {
> struct rpmsg_endpoint *ept;
> bool announce;
> bool little_endian;
> + bool us_removable;
>
> const struct rpmsg_device_ops *ops;
> };
> --
> 2.17.1
>
