![Dmytro Linkin](/assets/img/avatar_default.png)
Currently init call of all actions (except ipt) init their 'parm'
structure as a direct pointer to nla data in skb. This leads to race
condition when some of the filter actions were initialized successfully
(and were assigned with idr action index that was written directly
into nla data), but then were deleted and retried (due to following
action module missing or classifier-initiated retry), in which case
action init code tries to insert action to idr with index that was
assigned on previous iteration. During retry the index can be reused
by another action that was inserted concurrently, which causes
unintended action sharing between filters.
To fix described race condition, save action idr index to temporary
stack-allocated variable instead on nla data.
Fixes: 0190c1d452
("net: sched: atomically check-allocate action")
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
321 lines
7.9 KiB
C
321 lines
7.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* net/sched/act_skbmod.c skb data modifier
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*
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* Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
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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 <net/netlink.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_skbmod.h>
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#include <net/tc_act/tc_skbmod.h>
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static unsigned int skbmod_net_id;
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static struct tc_action_ops act_skbmod_ops;
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#define MAX_EDIT_LEN ETH_HLEN
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static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a,
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struct tcf_result *res)
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{
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struct tcf_skbmod *d = to_skbmod(a);
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int action;
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struct tcf_skbmod_params *p;
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u64 flags;
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int err;
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tcf_lastuse_update(&d->tcf_tm);
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bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
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/* XXX: if you are going to edit more fields beyond ethernet header
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* (example when you add IP header replacement or vlan swap)
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* then MAX_EDIT_LEN needs to change appropriately
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*/
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err = skb_ensure_writable(skb, MAX_EDIT_LEN);
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if (unlikely(err)) /* best policy is to drop on the floor */
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goto drop;
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action = READ_ONCE(d->tcf_action);
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if (unlikely(action == TC_ACT_SHOT))
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goto drop;
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p = rcu_dereference_bh(d->skbmod_p);
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flags = p->flags;
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if (flags & SKBMOD_F_DMAC)
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ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
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if (flags & SKBMOD_F_SMAC)
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ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
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if (flags & SKBMOD_F_ETYPE)
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eth_hdr(skb)->h_proto = p->eth_type;
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if (flags & SKBMOD_F_SWAPMAC) {
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u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
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/*XXX: I am sure we can come up with more efficient swapping*/
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ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
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ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
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ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
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}
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return action;
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drop:
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qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
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return TC_ACT_SHOT;
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}
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static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
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[TCA_SKBMOD_PARMS] = { .len = sizeof(struct tc_skbmod) },
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[TCA_SKBMOD_DMAC] = { .len = ETH_ALEN },
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[TCA_SKBMOD_SMAC] = { .len = ETH_ALEN },
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[TCA_SKBMOD_ETYPE] = { .type = NLA_U16 },
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};
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static int tcf_skbmod_init(struct net *net, struct nlattr *nla,
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struct nlattr *est, struct tc_action **a,
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int ovr, int bind, bool rtnl_held,
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struct tcf_proto *tp,
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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, skbmod_net_id);
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struct nlattr *tb[TCA_SKBMOD_MAX + 1];
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struct tcf_skbmod_params *p, *p_old;
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struct tcf_chain *goto_ch = NULL;
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struct tc_skbmod *parm;
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u32 lflags = 0, index;
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struct tcf_skbmod *d;
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bool exists = false;
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u8 *daddr = NULL;
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u8 *saddr = NULL;
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u16 eth_type = 0;
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int ret = 0, err;
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if (!nla)
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return -EINVAL;
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err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
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skbmod_policy, NULL);
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if (err < 0)
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return err;
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if (!tb[TCA_SKBMOD_PARMS])
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return -EINVAL;
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if (tb[TCA_SKBMOD_DMAC]) {
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daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
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lflags |= SKBMOD_F_DMAC;
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}
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if (tb[TCA_SKBMOD_SMAC]) {
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saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
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lflags |= SKBMOD_F_SMAC;
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}
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if (tb[TCA_SKBMOD_ETYPE]) {
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eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
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lflags |= SKBMOD_F_ETYPE;
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}
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parm = nla_data(tb[TCA_SKBMOD_PARMS]);
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index = parm->index;
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if (parm->flags & SKBMOD_F_SWAPMAC)
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lflags = SKBMOD_F_SWAPMAC;
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err = tcf_idr_check_alloc(tn, &index, a, bind);
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if (err < 0)
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return err;
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exists = err;
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if (exists && bind)
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return 0;
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if (!lflags) {
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if (exists)
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tcf_idr_release(*a, bind);
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else
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tcf_idr_cleanup(tn, index);
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return -EINVAL;
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}
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if (!exists) {
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ret = tcf_idr_create(tn, index, est, a,
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&act_skbmod_ops, bind, true);
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if (ret) {
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tcf_idr_cleanup(tn, index);
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return ret;
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}
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ret = ACT_P_CREATED;
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} else if (!ovr) {
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tcf_idr_release(*a, bind);
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return -EEXIST;
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}
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err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
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if (err < 0)
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goto release_idr;
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d = to_skbmod(*a);
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p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
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if (unlikely(!p)) {
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err = -ENOMEM;
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goto put_chain;
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}
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p->flags = lflags;
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if (ovr)
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spin_lock_bh(&d->tcf_lock);
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/* Protected by tcf_lock if overwriting existing action. */
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goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
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p_old = rcu_dereference_protected(d->skbmod_p, 1);
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if (lflags & SKBMOD_F_DMAC)
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ether_addr_copy(p->eth_dst, daddr);
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if (lflags & SKBMOD_F_SMAC)
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ether_addr_copy(p->eth_src, saddr);
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if (lflags & SKBMOD_F_ETYPE)
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p->eth_type = htons(eth_type);
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rcu_assign_pointer(d->skbmod_p, p);
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if (ovr)
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spin_unlock_bh(&d->tcf_lock);
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if (p_old)
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kfree_rcu(p_old, rcu);
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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if (ret == ACT_P_CREATED)
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tcf_idr_insert(tn, *a);
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return ret;
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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(*a, bind);
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return err;
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}
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static void tcf_skbmod_cleanup(struct tc_action *a)
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{
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struct tcf_skbmod *d = to_skbmod(a);
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struct tcf_skbmod_params *p;
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p = rcu_dereference_protected(d->skbmod_p, 1);
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if (p)
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kfree_rcu(p, rcu);
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}
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static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
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int bind, int ref)
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{
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struct tcf_skbmod *d = to_skbmod(a);
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unsigned char *b = skb_tail_pointer(skb);
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struct tcf_skbmod_params *p;
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struct tc_skbmod opt = {
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.index = d->tcf_index,
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.refcnt = refcount_read(&d->tcf_refcnt) - ref,
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.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
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};
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struct tcf_t t;
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spin_lock_bh(&d->tcf_lock);
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opt.action = d->tcf_action;
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p = rcu_dereference_protected(d->skbmod_p,
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lockdep_is_held(&d->tcf_lock));
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opt.flags = p->flags;
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if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
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goto nla_put_failure;
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if ((p->flags & SKBMOD_F_DMAC) &&
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nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
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goto nla_put_failure;
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if ((p->flags & SKBMOD_F_SMAC) &&
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nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
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goto nla_put_failure;
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if ((p->flags & SKBMOD_F_ETYPE) &&
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nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
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goto nla_put_failure;
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tcf_tm_dump(&t, &d->tcf_tm);
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if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_PAD))
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goto nla_put_failure;
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spin_unlock_bh(&d->tcf_lock);
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return skb->len;
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nla_put_failure:
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spin_unlock_bh(&d->tcf_lock);
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nlmsg_trim(skb, b);
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return -1;
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}
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static int tcf_skbmod_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, skbmod_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_skbmod_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, skbmod_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_skbmod_ops = {
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.kind = "skbmod",
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.id = TCA_ACT_SKBMOD,
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.owner = THIS_MODULE,
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.act = tcf_skbmod_act,
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.dump = tcf_skbmod_dump,
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.init = tcf_skbmod_init,
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.cleanup = tcf_skbmod_cleanup,
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.walk = tcf_skbmod_walker,
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.lookup = tcf_skbmod_search,
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.size = sizeof(struct tcf_skbmod),
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};
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static __net_init int skbmod_init_net(struct net *net)
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{
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struct tc_action_net *tn = net_generic(net, skbmod_net_id);
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return tc_action_net_init(tn, &act_skbmod_ops);
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}
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static void __net_exit skbmod_exit_net(struct list_head *net_list)
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{
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tc_action_net_exit(net_list, skbmod_net_id);
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}
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static struct pernet_operations skbmod_net_ops = {
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.init = skbmod_init_net,
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.exit_batch = skbmod_exit_net,
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.id = &skbmod_net_id,
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.size = sizeof(struct tc_action_net),
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};
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MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
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MODULE_DESCRIPTION("SKB data mod-ing");
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MODULE_LICENSE("GPL");
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static int __init skbmod_init_module(void)
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{
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return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
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}
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static void __exit skbmod_cleanup_module(void)
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{
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tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
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}
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module_init(skbmod_init_module);
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module_exit(skbmod_cleanup_module);
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