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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