在 2021/5/13 上午6:55, Alexei Starovoitov 写道:
On Wed, May 12, 2021 at 05:58:23PM +0800, Xufeng Zhang wrote:
To implement security rules for application containers by utilizing
bpf LSM, the container to which the current running task belongs need
to be known in bpf context. Think about this scenario: kubernetes
schedules a pod into one host, before the application container can run,
the security rules for this application need to be loaded into bpf
maps firstly, so that LSM bpf programs can make decisions based on
this rule maps.
However, there is no effective bpf helper to achieve this goal,
especially for cgroup v1. In the above case, the only available information
from user side is container-id, and the cgroup path for this container
is certain based on container-id, so in order to make a bridge between
user side and bpf programs, bpf programs also need to know the current
cgroup path of running task.
...
+#ifdef CONFIG_CGROUPS
+BPF_CALL_2(bpf_get_current_cpuset_cgroup_path, char *, buf, u32, buf_len)
+{
+ struct cgroup_subsys_state *css;
+ int retval;
+
+ css = task_get_css(current, cpuset_cgrp_id);
+ retval = cgroup_path_ns(css->cgroup, buf, buf_len, &init_cgroup_ns);
+ css_put(css);
+ if (retval >= buf_len)
+ retval = -ENAMETOOLONG;
Manipulating string path to check the hierarchy will be difficult to do
inside bpf prog. It seems to me this helper will be useful only for
simplest cgroup setups where there is no additional cgroup nesting
within containers.
Have you looked at *ancestor_cgroup_id and *cgroup_id helpers?
They're a bit more flexible when dealing with hierarchy and
can be used to achieve the same correlation between kernel and user cgroup ids.
Thanks for your timely reply, Alexei!
Yes, this helper is not so common, it does not works for nesting cgroup
within containers.
About your suggestion, the *cgroup_id helpers only works for cgroup v2,
however, we're still using cgroup v1 in product，and even for cgroup v2,
I'm not sure if there is any way for user space to get this cgroup id
timely(after container created, but before container start to run)。
So if there is any effective way works for cgroup v1?
Many thanks!
Xufeng
