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![Toke Høiland-Jørgensen](/assets/img/avatar_default.png)
The rcu_read_lock() call in cls_bpf and act_bpf are redundant: on the TX side, there's already a call to rcu_read_lock_bh() in __dev_queue_xmit(), and on RX there's a covering rcu_read_lock() in netif_receive_skb{,_list}_internal(). With the previous patches we also amended the lockdep checks in the map code to not require any particular RCU flavour, so we can just get rid of the rcu_read_lock()s. Suggested-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20210624160609.292325-7-toke@redhat.com
455 lines
10 KiB
C
455 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <linux/rtnetlink.h>
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#include <linux/filter.h>
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#include <linux/bpf.h>
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#include <net/netlink.h>
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#include <net/sock.h>
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#include <net/pkt_sched.h>
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#include <net/pkt_cls.h>
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#include <linux/tc_act/tc_bpf.h>
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#include <net/tc_act/tc_bpf.h>
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#define ACT_BPF_NAME_LEN 256
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struct tcf_bpf_cfg {
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struct bpf_prog *filter;
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struct sock_filter *bpf_ops;
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const char *bpf_name;
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u16 bpf_num_ops;
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bool is_ebpf;
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};
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static unsigned int bpf_net_id;
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static struct tc_action_ops act_bpf_ops;
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static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
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struct tcf_result *res)
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{
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bool at_ingress = skb_at_tc_ingress(skb);
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struct tcf_bpf *prog = to_bpf(act);
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struct bpf_prog *filter;
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int action, filter_res;
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tcf_lastuse_update(&prog->tcf_tm);
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bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
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filter = rcu_dereference(prog->filter);
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if (at_ingress) {
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__skb_push(skb, skb->mac_len);
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bpf_compute_data_pointers(skb);
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filter_res = BPF_PROG_RUN(filter, skb);
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__skb_pull(skb, skb->mac_len);
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} else {
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bpf_compute_data_pointers(skb);
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filter_res = BPF_PROG_RUN(filter, skb);
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}
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if (skb_sk_is_prefetched(skb) && filter_res != TC_ACT_OK)
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skb_orphan(skb);
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/* A BPF program may overwrite the default action opcode.
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* Similarly as in cls_bpf, if filter_res == -1 we use the
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* default action specified from tc.
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*
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* In case a different well-known TC_ACT opcode has been
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* returned, it will overwrite the default one.
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*
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* For everything else that is unknown, TC_ACT_UNSPEC is
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* returned.
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*/
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switch (filter_res) {
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case TC_ACT_PIPE:
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case TC_ACT_RECLASSIFY:
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case TC_ACT_OK:
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case TC_ACT_REDIRECT:
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action = filter_res;
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break;
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case TC_ACT_SHOT:
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action = filter_res;
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qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
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break;
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case TC_ACT_UNSPEC:
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action = prog->tcf_action;
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break;
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default:
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action = TC_ACT_UNSPEC;
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break;
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}
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return action;
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}
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static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
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{
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return !prog->bpf_ops;
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}
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static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
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struct sk_buff *skb)
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{
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struct nlattr *nla;
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if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
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return -EMSGSIZE;
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nla = nla_reserve(skb, TCA_ACT_BPF_OPS, prog->bpf_num_ops *
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sizeof(struct sock_filter));
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if (nla == NULL)
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return -EMSGSIZE;
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memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
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return 0;
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}
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static int tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
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struct sk_buff *skb)
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{
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struct nlattr *nla;
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if (prog->bpf_name &&
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nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
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return -EMSGSIZE;
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if (nla_put_u32(skb, TCA_ACT_BPF_ID, prog->filter->aux->id))
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return -EMSGSIZE;
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nla = nla_reserve(skb, TCA_ACT_BPF_TAG, sizeof(prog->filter->tag));
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if (nla == NULL)
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return -EMSGSIZE;
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memcpy(nla_data(nla), prog->filter->tag, nla_len(nla));
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return 0;
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}
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static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
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int bind, int ref)
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{
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unsigned char *tp = skb_tail_pointer(skb);
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struct tcf_bpf *prog = to_bpf(act);
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struct tc_act_bpf opt = {
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.index = prog->tcf_index,
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.refcnt = refcount_read(&prog->tcf_refcnt) - ref,
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.bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
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};
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struct tcf_t tm;
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int ret;
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spin_lock_bh(&prog->tcf_lock);
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opt.action = prog->tcf_action;
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if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
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goto nla_put_failure;
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if (tcf_bpf_is_ebpf(prog))
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ret = tcf_bpf_dump_ebpf_info(prog, skb);
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else
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ret = tcf_bpf_dump_bpf_info(prog, skb);
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if (ret)
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goto nla_put_failure;
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tcf_tm_dump(&tm, &prog->tcf_tm);
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if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
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TCA_ACT_BPF_PAD))
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goto nla_put_failure;
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spin_unlock_bh(&prog->tcf_lock);
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return skb->len;
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nla_put_failure:
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spin_unlock_bh(&prog->tcf_lock);
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nlmsg_trim(skb, tp);
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return -1;
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}
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static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
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[TCA_ACT_BPF_PARMS] = { .len = sizeof(struct tc_act_bpf) },
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[TCA_ACT_BPF_FD] = { .type = NLA_U32 },
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[TCA_ACT_BPF_NAME] = { .type = NLA_NUL_STRING,
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.len = ACT_BPF_NAME_LEN },
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[TCA_ACT_BPF_OPS_LEN] = { .type = NLA_U16 },
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[TCA_ACT_BPF_OPS] = { .type = NLA_BINARY,
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.len = sizeof(struct sock_filter) * BPF_MAXINSNS },
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};
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static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
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{
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struct sock_filter *bpf_ops;
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struct sock_fprog_kern fprog_tmp;
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struct bpf_prog *fp;
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u16 bpf_size, bpf_num_ops;
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int ret;
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bpf_num_ops = nla_get_u16(tb[TCA_ACT_BPF_OPS_LEN]);
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if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
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return -EINVAL;
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bpf_size = bpf_num_ops * sizeof(*bpf_ops);
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if (bpf_size != nla_len(tb[TCA_ACT_BPF_OPS]))
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return -EINVAL;
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bpf_ops = kmemdup(nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size, GFP_KERNEL);
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if (bpf_ops == NULL)
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return -ENOMEM;
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fprog_tmp.len = bpf_num_ops;
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fprog_tmp.filter = bpf_ops;
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ret = bpf_prog_create(&fp, &fprog_tmp);
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if (ret < 0) {
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kfree(bpf_ops);
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return ret;
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}
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cfg->bpf_ops = bpf_ops;
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cfg->bpf_num_ops = bpf_num_ops;
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cfg->filter = fp;
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cfg->is_ebpf = false;
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return 0;
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}
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static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
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{
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struct bpf_prog *fp;
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char *name = NULL;
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u32 bpf_fd;
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bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);
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fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
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if (IS_ERR(fp))
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return PTR_ERR(fp);
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if (tb[TCA_ACT_BPF_NAME]) {
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name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
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if (!name) {
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bpf_prog_put(fp);
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return -ENOMEM;
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}
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}
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cfg->bpf_name = name;
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cfg->filter = fp;
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cfg->is_ebpf = true;
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return 0;
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}
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static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
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{
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struct bpf_prog *filter = cfg->filter;
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if (filter) {
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if (cfg->is_ebpf)
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bpf_prog_put(filter);
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else
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bpf_prog_destroy(filter);
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}
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kfree(cfg->bpf_ops);
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kfree(cfg->bpf_name);
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}
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static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
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struct tcf_bpf_cfg *cfg)
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{
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cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
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/* updates to prog->filter are prevented, since it's called either
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* with tcf lock or during final cleanup in rcu callback
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*/
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cfg->filter = rcu_dereference_protected(prog->filter, 1);
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cfg->bpf_ops = prog->bpf_ops;
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cfg->bpf_name = prog->bpf_name;
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}
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static int tcf_bpf_init(struct net *net, struct nlattr *nla,
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struct nlattr *est, struct tc_action **act,
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int replace, int bind, bool rtnl_held,
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struct tcf_proto *tp, u32 flags,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, bpf_net_id);
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struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
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struct tcf_chain *goto_ch = NULL;
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struct tcf_bpf_cfg cfg, old;
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struct tc_act_bpf *parm;
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struct tcf_bpf *prog;
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bool is_bpf, is_ebpf;
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int ret, res = 0;
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u32 index;
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if (!nla)
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return -EINVAL;
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ret = nla_parse_nested_deprecated(tb, TCA_ACT_BPF_MAX, nla,
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act_bpf_policy, NULL);
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if (ret < 0)
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return ret;
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if (!tb[TCA_ACT_BPF_PARMS])
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return -EINVAL;
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parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
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index = parm->index;
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ret = tcf_idr_check_alloc(tn, &index, act, bind);
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if (!ret) {
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ret = tcf_idr_create(tn, index, est, act,
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&act_bpf_ops, bind, true, 0);
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if (ret < 0) {
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tcf_idr_cleanup(tn, index);
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return ret;
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}
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res = ACT_P_CREATED;
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} else if (ret > 0) {
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/* Don't override defaults. */
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if (bind)
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return 0;
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if (!replace) {
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tcf_idr_release(*act, bind);
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return -EEXIST;
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}
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} else {
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return ret;
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}
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ret = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
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if (ret < 0)
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goto release_idr;
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is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
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is_ebpf = tb[TCA_ACT_BPF_FD];
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if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
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ret = -EINVAL;
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goto put_chain;
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}
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memset(&cfg, 0, sizeof(cfg));
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ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
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tcf_bpf_init_from_efd(tb, &cfg);
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if (ret < 0)
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goto put_chain;
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prog = to_bpf(*act);
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spin_lock_bh(&prog->tcf_lock);
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if (res != ACT_P_CREATED)
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tcf_bpf_prog_fill_cfg(prog, &old);
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prog->bpf_ops = cfg.bpf_ops;
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prog->bpf_name = cfg.bpf_name;
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if (cfg.bpf_num_ops)
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prog->bpf_num_ops = cfg.bpf_num_ops;
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goto_ch = tcf_action_set_ctrlact(*act, parm->action, goto_ch);
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rcu_assign_pointer(prog->filter, cfg.filter);
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spin_unlock_bh(&prog->tcf_lock);
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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if (res != ACT_P_CREATED) {
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/* make sure the program being replaced is no longer executing */
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synchronize_rcu();
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tcf_bpf_cfg_cleanup(&old);
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}
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return res;
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put_chain:
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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release_idr:
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tcf_idr_release(*act, bind);
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return ret;
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}
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static void tcf_bpf_cleanup(struct tc_action *act)
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{
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struct tcf_bpf_cfg tmp;
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tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
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tcf_bpf_cfg_cleanup(&tmp);
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}
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static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
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struct netlink_callback *cb, int type,
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const struct tc_action_ops *ops,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, bpf_net_id);
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return tcf_generic_walker(tn, skb, cb, type, ops, extack);
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}
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static int tcf_bpf_search(struct net *net, struct tc_action **a, u32 index)
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{
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struct tc_action_net *tn = net_generic(net, bpf_net_id);
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return tcf_idr_search(tn, a, index);
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}
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static struct tc_action_ops act_bpf_ops __read_mostly = {
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.kind = "bpf",
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.id = TCA_ID_BPF,
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.owner = THIS_MODULE,
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.act = tcf_bpf_act,
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.dump = tcf_bpf_dump,
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.cleanup = tcf_bpf_cleanup,
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.init = tcf_bpf_init,
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.walk = tcf_bpf_walker,
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.lookup = tcf_bpf_search,
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.size = sizeof(struct tcf_bpf),
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};
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static __net_init int bpf_init_net(struct net *net)
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{
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struct tc_action_net *tn = net_generic(net, bpf_net_id);
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return tc_action_net_init(net, tn, &act_bpf_ops);
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}
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static void __net_exit bpf_exit_net(struct list_head *net_list)
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{
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tc_action_net_exit(net_list, bpf_net_id);
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}
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static struct pernet_operations bpf_net_ops = {
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.init = bpf_init_net,
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.exit_batch = bpf_exit_net,
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.id = &bpf_net_id,
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.size = sizeof(struct tc_action_net),
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};
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static int __init bpf_init_module(void)
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{
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return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
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}
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static void __exit bpf_cleanup_module(void)
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{
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tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
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}
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module_init(bpf_init_module);
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module_exit(bpf_cleanup_module);
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MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
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MODULE_DESCRIPTION("TC BPF based action");
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MODULE_LICENSE("GPL v2");
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