On Fri, Feb 04, 2022 at 09:53:38AM +0300, Anton V. Boyarshinov wrote:
> Idmapped mounts may have security implications [1] and have
> no knobs to be disallowed at runtime or compile time.
>
> This patch adds a sysctl and a config option to set its default value.
>
> [1] https://lore.kernel.org/all/[email protected]/
>
> Based on work from Alexey Gladkov <[email protected]>.
>
> Signed-off-by: Anton V. Boyarshinov <[email protected]>
> ---
Thank your for the general idea, Anton.
If you want to turn off idmapped mounts you can already do so today via:
echo 0 > /proc/sys/user/max_user_namespaces
Aside from that, idmapped mounts can only be created by fully privileged
users on the host for a selected number of filesystems. They can neither
be created as an unprivileged user nor can they be created inside user
namespaces.
I appreciate the worry. Any new feature may have security implications
and bugs. In addition, we did address these allegations multiple times
already (see [1], [2], [3], [4], [5]).
As the author/maintainer of this feature,
Nacked-by: Christian Brauner <[email protected]>
[1]: https://lore.kernel.org/lkml/[email protected]/T/#m3a9df31aa183e8797c70bc193040adfd601399ad
[2]: https://lore.kernel.org/lkml/[email protected]
[3]: https://lore.kernel.org/lkml/[email protected]/T/#m59cdad9630d5a279aeecd0c1f117115144bc15eb
[4]: https://lore.kernel.org/lkml/20210510125147.tkgeurcindldiwxg@wittgenstein
[5]: https://lore.kernel.org/linux-fsdevel/CAHrFyr4AYi_gad7LQ-cJ9Peg=Gt73Sded8k_ZHeRZz=faGzpQA@mail.gmail.com
В Fri, 4 Feb 2022 10:45:15 +0100
Christian Brauner <[email protected]> пишет:
> If you want to turn off idmapped mounts you can already do so today via:
> echo 0 > /proc/sys/user/max_user_namespaces
It turns off much more than idmapped mounts only. More fine grained
control seems better for me.
> They can neither
> be created as an unprivileged user nor can they be created inside user
> namespaces.
But actions of fully privileged user can open non-obvious ways to
privilege escalation.