Re: [PATCH 09/11] fs: reorder capability check last

From: Christian Brauner
Date: Mon Nov 25 2024 - 07:17:47 EST


On Mon, Nov 25, 2024 at 11:40:01AM +0100, Christian Göttsche wrote:
> From: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
>
> capable() calls refer to enabled LSMs whether to permit or deny the
> request. This is relevant in connection with SELinux, where a
> capability check results in a policy decision and by default a denial
> message on insufficient permission is issued.
> It can lead to three undesired cases:
> 1. A denial message is generated, even in case the operation was an
> unprivileged one and thus the syscall succeeded, creating noise.
> 2. To avoid the noise from 1. the policy writer adds a rule to ignore
> those denial messages, hiding future syscalls, where the task
> performs an actual privileged operation, leading to hidden limited
> functionality of that task.
> 3. To avoid the noise from 1. the policy writer adds a rule to permit
> the task the requested capability, while it does not need it,
> violating the principle of least privilege.
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
> ---

Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>