Commit 4a482f34 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

cgroup: bpf: Add bpf_skb_in_cgroup_proto 



Adds a bpf helper, bpf_skb_in_cgroup, to decide if a skb->sk
belongs to a descendant of a cgroup2.  It is similar to the
feature added in netfilter:
commit c38c4597 ("netfilter: implement xt_cgroup cgroup2 path match")

The user is expected to populate a BPF_MAP_TYPE_CGROUP_ARRAY
which will be used by the bpf_skb_in_cgroup.

Modifications to the bpf verifier is to ensure BPF_MAP_TYPE_CGROUP_ARRAY
and bpf_skb_in_cgroup() are always used together.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4ed8ec52

include/uapi/linux/bpf.h

+11 −0
Original line number Diff line number Diff line
@@ -337,6 +337,17 @@ enum bpf_func_id { 
	 */

	BPF_FUNC_skb_change_type,



	/**

	 * bpf_skb_in_cgroup(skb, map, index) - Check cgroup2 membership of skb

	 * @skb: pointer to skb

	 * @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type

	 * @index: index of the cgroup in the bpf_map

	 * Return:

	 *   == 0 skb failed the cgroup2 descendant test

	 *   == 1 skb succeeded the cgroup2 descendant test

	 *    < 0 error

	 */

	BPF_FUNC_skb_in_cgroup,

	__BPF_FUNC_MAX_ID,

};

kernel/bpf/verifier.c

+7 −1
Original line number Diff line number Diff line
@@ -1036,7 +1036,9 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id) 
			goto error;

		break;

	case BPF_MAP_TYPE_CGROUP_ARRAY:

		if (func_id != BPF_FUNC_skb_in_cgroup)

			goto error;

		break;

	default:

		break;

	}
@@ -1056,6 +1058,10 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id) 
		if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)

			goto error;

		break;

	case BPF_FUNC_skb_in_cgroup:

		if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)

			goto error;

		break;

	default:

		break;

	}

net/core/filter.c

+38 −0
Original line number Diff line number Diff line
@@ -2239,6 +2239,40 @@ bpf_get_skb_set_tunnel_proto(enum bpf_func_id which) 
	}

}



#ifdef CONFIG_SOCK_CGROUP_DATA

static u64 bpf_skb_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)

{

	struct sk_buff *skb = (struct sk_buff *)(long)r1;

	struct bpf_map *map = (struct bpf_map *)(long)r2;

	struct bpf_array *array = container_of(map, struct bpf_array, map);

	struct cgroup *cgrp;

	struct sock *sk;

	u32 i = (u32)r3;



	sk = skb->sk;

	if (!sk || !sk_fullsock(sk))

		return -ENOENT;



	if (unlikely(i >= array->map.max_entries))

		return -E2BIG;



	cgrp = READ_ONCE(array->ptrs[i]);

	if (unlikely(!cgrp))

		return -EAGAIN;



	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);

}



static const struct bpf_func_proto bpf_skb_in_cgroup_proto = {

	.func		= bpf_skb_in_cgroup,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_CTX,

	.arg2_type	= ARG_CONST_MAP_PTR,

	.arg3_type	= ARG_ANYTHING,

};

#endif



static const struct bpf_func_proto *

sk_filter_func_proto(enum bpf_func_id func_id)

{
@@ -2307,6 +2341,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id) 
		return bpf_get_event_output_proto();

	case BPF_FUNC_get_smp_processor_id:

		return &bpf_get_smp_processor_id_proto;

#ifdef CONFIG_SOCK_CGROUP_DATA

	case BPF_FUNC_skb_in_cgroup:

		return &bpf_skb_in_cgroup_proto;

#endif

	default:

		return sk_filter_func_proto(func_id);

	}

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