On Fri, 2020-09-04 at 11:10 +0200, Ilya Dryomov wrote:
> It turns out that currently we rely only on sysfs attribute
> permissions:
>
> $ ll /sys/bus/rbd/{add*,remove*}
> --w------- 1 root root 4096 Sep 3 20:37 /sys/bus/rbd/add
> --w------- 1 root root 4096 Sep 3 20:37 /sys/bus/rbd/add_single_major
> --w------- 1 root root 4096 Sep 3 20:37 /sys/bus/rbd/remove
> --w------- 1 root root 4096 Sep 3 20:38 /sys/bus/rbd/remove_single_major
>
> This means that images can be mapped and unmapped (i.e. block devices
> can be created and deleted) by a UID 0 process even after it drops all
> privileges or by any process with CAP_DAC_OVERRIDE in its user namespace
> as long as UID 0 is mapped into that user namespace.
>
> Be consistent with other virtual block devices (loop, nbd, dm, md, etc)
> and require CAP_SYS_ADMIN in the initial user namespace for mapping and
> unmapping, and also for dumping the configuration string and refreshing
> the image header.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> ---
> drivers/block/rbd.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index fa252e8ed276..180587ce606c 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -5120,6 +5120,9 @@ static ssize_t rbd_config_info_show(struct device *dev,
> {
> struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
>
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> return sprintf(buf, "%s\n", rbd_dev->config_info);
> }
>
> @@ -5231,6 +5234,9 @@ static ssize_t rbd_image_refresh(struct device *dev,
> struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
> int ret;
>
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> ret = rbd_dev_refresh(rbd_dev);
> if (ret)
> return ret;
> @@ -7059,6 +7065,9 @@ static ssize_t do_rbd_add(struct bus_type *bus,
> struct rbd_client *rbdc;
> int rc;
>
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> if (!try_module_get(THIS_MODULE))
> return -ENODEV;
>
> @@ -7209,6 +7218,9 @@ static ssize_t do_rbd_remove(struct bus_type *bus,
> bool force = false;
> int ret;
>
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> dev_id = -1;
> opt_buf[0] = '\0';
> sscanf(buf, "%d %5s", &dev_id, opt_buf);
Good catch!
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
