Messages in this thread | | | Subject | Re: [RFC] [PATCH bpf-next 1/1] bpf: Add a BPF helper for getting the cgroup path of current task | From | xufeng zhang <> | Date | Fri, 14 May 2021 12:06:29 +0800 |
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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.
KP,
do you have any suggestion?
what I am thinking is the internal kernel object(cgroup id or ns.inum) is not so user friendly, we can get the container-context from them for tracing scenario, but not for LSM blocking cases, I'm not sure how Google internally resolve similar issue.
Thanks!
Xufeng
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