Messages in this thread | | | Date | Thu, 23 Jun 2016 22:07:27 +0200 | From | Daniel Borkmann <> | Subject | Re: [PATCH net-next v2 3/4] cgroup: bpf: Add bpf_skb_in_cgroup_proto |
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On 06/23/2016 06:54 PM, Martin KaFai Lau wrote: > On Thu, Jun 23, 2016 at 11:53:50AM +0200, Daniel Borkmann wrote: >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index 668e079..68753e0 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -1062,6 +1062,10 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id) >>> if (func_id != BPF_FUNC_get_stackid) >>> goto error; >>> break; >>> + case BPF_MAP_TYPE_CGROUP_ARRAY: >>> + if (func_id != BPF_FUNC_skb_in_cgroup) >>> + goto error; >>> + break; >> >> I think the BPF_MAP_TYPE_CGROUP_ARRAY case should have been fist here in >> patch 2/4, but with unconditional goto error. And this one only adds the >> 'func_id != BPF_FUNC_skb_in_cgroup' test. > I am not sure I understand. Can you elaborate? I am probably missing > something here.
If someone backports patch 2/4 as-is, but for some reason not 3/4, then you could craft a program that calls f.e. bpf_map_update_elem() on a cgroup array and would thus cause a NULL pointer deref, since verifier doesn't prevent it. I'm just trying to say that it would probably make sense to add the above 'case BPF_MAP_TYPE_CGROUP_ARRAY:' with an unconditional 'goto error' in patch 2/4 and extend upon it in patch 3/4 so result looks like here, so that the patches are fine/complete each as stand-alone.
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