From: Daniel Borkmann <daniel@iogearbox•net>
To: Daniel Mack <daniel@zonque•org>, htejun@fb•com, ast@fb•com
Cc: davem@davemloft•net, kafai@fb•com, fw@strlen•de,
pablo@netfilter•org, harald@redhat•com, netdev@vger•kernel.org,
sargun@sargun•me
Subject: Re: [PATCH v3 2/6] cgroup: add support for eBPF programs
Date: Tue, 30 Aug 2016 00:42:10 +0200 [thread overview]
Message-ID: <57C4BA42.2090300@iogearbox.net> (raw)
In-Reply-To: <1472241532-11682-3-git-send-email-daniel@zonque.org>
On 08/26/2016 09:58 PM, Daniel Mack wrote:
> This patch adds two sets of eBPF program pointers to struct cgroup.
> One for such that are directly pinned to a cgroup, and one for such
> that are effective for it.
>
> To illustrate the logic behind that, assume the following example
> cgroup hierarchy.
>
> A - B - C
> \ D - E
>
> If only B has a program attached, it will be effective for B, C, D
> and E. If D then attaches a program itself, that will be effective for
> both D and E, and the program in B will only affect B and C. Only one
> program of a given type is effective for a cgroup.
>
> Attaching and detaching programs will be done through the bpf(2)
> syscall. For now, ingress and egress inet socket filtering are the
> only supported use-cases.
>
> Signed-off-by: Daniel Mack <daniel@zonque•org>
[...]
> +void __cgroup_bpf_update(struct cgroup *cgrp,
> + struct cgroup *parent,
> + struct bpf_prog *prog,
> + enum bpf_attach_type type)
> +{
> + struct bpf_prog *old_prog, *effective;
> + struct cgroup_subsys_state *pos;
> +
> + old_prog = xchg(cgrp->bpf.prog + type, prog);
> +
> + if (prog)
> + static_branch_inc(&cgroup_bpf_enabled_key);
> +
> + if (old_prog) {
> + bpf_prog_put(old_prog);
> + static_branch_dec(&cgroup_bpf_enabled_key);
> + }
> +
> + effective = (!prog && parent) ?
> + rcu_dereference_protected(parent->bpf.effective[type],
> + lockdep_is_held(&cgroup_mutex)) :
> + prog;
> +
> + css_for_each_descendant_pre(pos, &cgrp->self) {
> + struct cgroup *desc = container_of(pos, struct cgroup, self);
> +
> + /* skip the subtree if the descendant has its own program */
> + if (desc->bpf.prog[type] && desc != cgrp)
> + pos = css_rightmost_descendant(pos);
> + else
> + rcu_assign_pointer(desc->bpf.effective[type],
> + effective);
> + }
Shouldn't the old_prog reference only be released right here at the end
instead of above (otherwise this could race)?
> +}
next prev parent reply other threads:[~2016-08-29 22:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-26 19:58 [PATCH v3 0/6] Add eBPF hooks for cgroups Daniel Mack
2016-08-26 19:58 ` [PATCH v3 1/6] bpf: add new prog type for cgroup socket filtering Daniel Mack
2016-08-29 22:14 ` Daniel Borkmann
2016-09-05 12:48 ` Daniel Mack
2016-08-26 19:58 ` [PATCH v3 2/6] cgroup: add support for eBPF programs Daniel Mack
2016-08-27 0:03 ` Alexei Starovoitov
2016-09-05 12:47 ` Daniel Mack
2016-08-29 22:42 ` Daniel Borkmann [this message]
2016-09-05 12:50 ` Daniel Mack
2016-08-29 23:04 ` Sargun Dhillon
2016-09-05 14:49 ` Daniel Mack
2016-09-05 21:40 ` Sargun Dhillon
2016-09-05 22:39 ` Alexei Starovoitov
2016-08-26 19:58 ` [PATCH v3 3/6] bpf: add BPF_PROG_ATTACH and BPF_PROG_DETACH commands Daniel Mack
2016-08-27 0:08 ` Alexei Starovoitov
2016-09-05 12:56 ` Daniel Mack
2016-09-05 15:30 ` David Laight
2016-09-05 15:40 ` Daniel Mack
2016-09-05 17:29 ` Joe Perches
2016-08-29 23:00 ` Daniel Borkmann
2016-09-05 12:54 ` Daniel Mack
2016-09-05 13:56 ` Daniel Borkmann
2016-09-05 14:09 ` Daniel Mack
2016-09-05 17:09 ` Daniel Borkmann
2016-09-05 18:32 ` Alexei Starovoitov
2016-09-05 18:43 ` Daniel Mack
2016-08-26 19:58 ` [PATCH v3 4/6] net: filter: run cgroup eBPF ingress programs Daniel Mack
2016-08-29 23:15 ` Daniel Borkmann
2016-08-26 19:58 ` [PATCH v3 5/6] net: core: run cgroup eBPF egress programs Daniel Mack
2016-08-29 22:03 ` Daniel Borkmann
2016-08-29 22:23 ` Sargun Dhillon
2016-09-05 14:22 ` Daniel Mack
2016-09-06 17:14 ` Daniel Borkmann
2016-08-26 19:58 ` [PATCH v3 6/6] samples: bpf: add userspace example for attaching eBPF programs to cgroups Daniel Mack
2016-08-27 13:00 ` [PATCH v3 0/6] Add eBPF hooks for cgroups Rami Rosen
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