On Fri, Mar 27, 2020 at 8:59 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> Enable the bpf_get_current_cgroup_id() helper for connect(), sendmsg(),
> recvmsg() and bind-related hooks in order to retrieve the cgroup v2
> context which can then be used as part of the key for BPF map lookups,
> for example. Given these hooks operate in process context 'current' is
> always valid and pointing to the app that is performing mentioned
> syscalls if it's subject to a v2 cgroup. Also with same motivation of
> commit 7723628101aa ("bpf: Introduce bpf_skb_ancestor_cgroup_id helper")
> enable retrieval of ancestor from current so the cgroup id can be used
> for policy lookups which can then forbid connect() / bind(), for example.
>
> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> ---
Same question about just directly getting this from current through CO-RE.
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 21 ++++++++++++++++++++-
> kernel/bpf/core.c | 1 +
> kernel/bpf/helpers.c | 18 ++++++++++++++++++
> net/core/filter.c | 12 ++++++++++++
> tools/include/uapi/linux/bpf.h | 21 ++++++++++++++++++++-
> 6 files changed, 72 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 78046c570596..372708eeaecd 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1501,6 +1501,7 @@ extern const struct bpf_func_proto bpf_get_stack_proto;
> extern const struct bpf_func_proto bpf_sock_map_update_proto;
> extern const struct bpf_func_proto bpf_sock_hash_update_proto;
> extern const struct bpf_func_proto bpf_get_current_cgroup_id_proto;
> +extern const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto;
> extern const struct bpf_func_proto bpf_msg_redirect_hash_proto;
> extern const struct bpf_func_proto bpf_msg_redirect_map_proto;
> extern const struct bpf_func_proto bpf_sk_redirect_hash_proto;
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index bd81c4555206..222ba11966e3 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2963,6 +2963,24 @@ union bpf_attr {
> * instead of sockets.
> * Return
> * A 8-byte long opaque number.
> + *
> + * u64 bpf_get_current_ancestor_cgroup_id(int ancestor_level)
> + * Description
> + * Return id of cgroup v2 that is ancestor of the cgroup associated
> + * with the current task at the *ancestor_level*. The root cgroup
> + * is at *ancestor_level* zero and each step down the hierarchy
> + * increments the level. If *ancestor_level* == level of cgroup
> + * associated with the current task, then return value will be the
> + * same as that of **bpf_get_current_cgroup_id**\ ().
> + *
> + * The helper is useful to implement policies based on cgroups
> + * that are upper in hierarchy than immediate cgroup associated
> + * with the current task.
> + *
> + * The format of returned id and helper limitations are same as in
> + * **bpf_get_current_cgroup_id**\ ().
> + * Return
> + * The id is returned or 0 in case the id could not be retrieved.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3087,7 +3105,8 @@ union bpf_attr {
> FN(read_branch_records), \
> FN(get_ns_current_pid_tgid), \
> FN(xdp_output), \
> - FN(get_netns_cookie),
> + FN(get_netns_cookie), \
> + FN(get_current_ancestor_cgroup_id),
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> * function eBPF program intends to call
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 914f3463aa41..916f5132a984 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -2156,6 +2156,7 @@ const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak;
> const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak;
> const struct bpf_func_proto bpf_get_current_comm_proto __weak;
> const struct bpf_func_proto bpf_get_current_cgroup_id_proto __weak;
> +const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto __weak;
> const struct bpf_func_proto bpf_get_local_storage_proto __weak;
> const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto __weak;
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 01878db15eaf..bafc53ddd350 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -340,6 +340,24 @@ const struct bpf_func_proto bpf_get_current_cgroup_id_proto = {
> .ret_type = RET_INTEGER,
> };
>
> +BPF_CALL_1(bpf_get_current_ancestor_cgroup_id, int, ancestor_level)
> +{
> + struct cgroup *cgrp = task_dfl_cgroup(current);
> + struct cgroup *ancestor;
> +
> + ancestor = cgroup_ancestor(cgrp, ancestor_level);
> + if (!ancestor)
> + return 0;
> + return cgroup_id(ancestor);
> +}
> +
> +const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto = {
> + .func = bpf_get_current_ancestor_cgroup_id,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_ANYTHING,
> +};
> +
> #ifdef CONFIG_CGROUP_BPF
> DECLARE_PER_CPU(struct bpf_cgroup_storage*,
> bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 3083c7746ee0..5cec3ac9e3dd 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6018,6 +6018,12 @@ sock_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> return &bpf_get_netns_cookie_sock_proto;
> case BPF_FUNC_perf_event_output:
> return &bpf_event_output_data_proto;
> +#ifdef CONFIG_CGROUPS
> + case BPF_FUNC_get_current_cgroup_id:
> + return &bpf_get_current_cgroup_id_proto;
> + case BPF_FUNC_get_current_ancestor_cgroup_id:
> + return &bpf_get_current_ancestor_cgroup_id_proto;
> +#endif
> #ifdef CONFIG_CGROUP_NET_CLASSID
> case BPF_FUNC_get_cgroup_classid:
> return &bpf_get_cgroup_classid_curr_proto;
> @@ -6052,6 +6058,12 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> return &bpf_get_local_storage_proto;
> case BPF_FUNC_perf_event_output:
> return &bpf_event_output_data_proto;
> +#ifdef CONFIG_CGROUPS
> + case BPF_FUNC_get_current_cgroup_id:
> + return &bpf_get_current_cgroup_id_proto;
> + case BPF_FUNC_get_current_ancestor_cgroup_id:
> + return &bpf_get_current_ancestor_cgroup_id_proto;
> +#endif
> #ifdef CONFIG_CGROUP_NET_CLASSID
> case BPF_FUNC_get_cgroup_classid:
> return &bpf_get_cgroup_classid_curr_proto;
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index bd81c4555206..222ba11966e3 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -2963,6 +2963,24 @@ union bpf_attr {
> * instead of sockets.
> * Return
> * A 8-byte long opaque number.
> + *
> + * u64 bpf_get_current_ancestor_cgroup_id(int ancestor_level)
> + * Description
> + * Return id of cgroup v2 that is ancestor of the cgroup associated
> + * with the current task at the *ancestor_level*. The root cgroup
> + * is at *ancestor_level* zero and each step down the hierarchy
> + * increments the level. If *ancestor_level* == level of cgroup
> + * associated with the current task, then return value will be the
> + * same as that of **bpf_get_current_cgroup_id**\ ().
> + *
> + * The helper is useful to implement policies based on cgroups
> + * that are upper in hierarchy than immediate cgroup associated
> + * with the current task.
> + *
> + * The format of returned id and helper limitations are same as in
> + * **bpf_get_current_cgroup_id**\ ().
> + * Return
> + * The id is returned or 0 in case the id could not be retrieved.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3087,7 +3105,8 @@ union bpf_attr {
> FN(read_branch_records), \
> FN(get_ns_current_pid_tgid), \
> FN(xdp_output), \
> - FN(get_netns_cookie),
> + FN(get_netns_cookie), \
> + FN(get_current_ancestor_cgroup_id),
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> * function eBPF program intends to call
> --
> 2.21.0
>
