[PATCH bpf-next] bpf: permit CGROUP_DEVICE programs accessing helper bpf_get_current_cgroup_id()

[Yonghong Song <yhs@fb.com>]

Currently, helper bpf_get_current_cgroup_id() is not permitted
for CGROUP_DEVICE type of programs. If the helper is used
in such cases, the verifier will log the following error:

  0: (bf) r6 = r1
  1: (69) r7 = *(u16 *)(r6 +0)
  2: (85) call bpf_get_current_cgroup_id#80
  unknown func bpf_get_current_cgroup_id#80

The bpf_get_current_cgroup_id() is useful for CGROUP_DEVICE
type of programs in order to customize action based on cgroup id.
This patch added such a support.

Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/cgroup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 065c3d9ff8eb..00f6ed2e4f9a 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -707,6 +707,8 @@ cgroup_dev_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_get_current_uid_gid_proto;
 	case BPF_FUNC_get_local_storage:
 		return &bpf_get_local_storage_proto;
+	case BPF_FUNC_get_current_cgroup_id:
+		return &bpf_get_current_cgroup_id_proto;
 	case BPF_FUNC_trace_printk:
 		if (capable(CAP_SYS_ADMIN))
 			return bpf_get_trace_printk_proto();
-- 
2.17.1