[Devel] [PATCH RH7 1/2] device_cgroup: fake allowing all devices for docker inside VZCT

[Vladimir Davydov]

On Wed, Oct 07, 2015 at 11:51:06AM +0300, Pavel Tikhomirov wrote:
> Docker from 1.7.0 tries to add "a" to devices.allow for newly created
> privileged container device_cgroup, and thus to allow all devices in
> docker container. Docker fails to do so because not all devices are
> allowed in parent VZCT cgroup.
> 
> To support docker we must allow writing "a" to devices.allow in CT.
> With this patch if we get "a", we will silently exit without EPERM.
> 
> https://jira.sw.ru/browse/PSBM-38691

It is worth mentioning that this patch is a port of PCS6 commit
diff-device_cgroup-fake-allowing-all-devices-for-docker-inside-VZCT

> 
> v2: fix bug link, fix comment stile
> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
> ---
>  security/device_cgroup.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 531e40c..9f932d7 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -689,7 +689,14 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
>  			if (has_children(devcgroup))
>  				return -EINVAL;
>  
> -			if (!may_allow_all(parent))
> +			if (!may_allow_all(parent)) {
> +				if (ve_is_super(get_exec_env()))
> +					return -EPERM;
> +				else
> +					/* Fooling docker in CT - silently exit */
> +					return 0;
> +			}
> +

>  				return -EPERM;

You seem to have forgotten to remove this line.

>  			dev_exception_clean(devcgroup);
>  			devcgroup->behavior = DEVCG_DEFAULT_ALLOW;