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linux-next/net/sched/act_simple.c
Dmytro Linkin 7be8ef2cdb net: sched: use temporary variable for actions indexes
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>
2019-08-05 10:59:14 -07:00

269 lines
6.4 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* net/sched/act_simple.c Simple example of an action
*
* Authors: Jamal Hadi Salim (2005-8)
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <linux/tc_act/tc_defact.h>
#include <net/tc_act/tc_defact.h>
static unsigned int simp_net_id;
static struct tc_action_ops act_simp_ops;
#define SIMP_MAX_DATA 32
static int tcf_simp_act(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_defact *d = to_defact(a);
spin_lock(&d->tcf_lock);
tcf_lastuse_update(&d->tcf_tm);
bstats_update(&d->tcf_bstats, skb);
/* print policy string followed by _ then packet count
* Example if this was the 3rd packet and the string was "hello"
* then it would look like "hello_3" (without quotes)
*/
pr_info("simple: %s_%d\n",
(char *)d->tcfd_defdata, d->tcf_bstats.packets);
spin_unlock(&d->tcf_lock);
return d->tcf_action;
}
static void tcf_simp_release(struct tc_action *a)
{
struct tcf_defact *d = to_defact(a);
kfree(d->tcfd_defdata);
}
static int alloc_defdata(struct tcf_defact *d, const struct nlattr *defdata)
{
d->tcfd_defdata = kzalloc(SIMP_MAX_DATA, GFP_KERNEL);
if (unlikely(!d->tcfd_defdata))
return -ENOMEM;
nla_strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
return 0;
}
static int reset_policy(struct tc_action *a, const struct nlattr *defdata,
struct tc_defact *p, struct tcf_proto *tp,
struct netlink_ext_ack *extack)
{
struct tcf_chain *goto_ch = NULL;
struct tcf_defact *d;
int err;
err = tcf_action_check_ctrlact(p->action, tp, &goto_ch, extack);
if (err < 0)
return err;
d = to_defact(a);
spin_lock_bh(&d->tcf_lock);
goto_ch = tcf_action_set_ctrlact(a, p->action, goto_ch);
memset(d->tcfd_defdata, 0, SIMP_MAX_DATA);
nla_strlcpy(d->tcfd_defdata, defdata, SIMP_MAX_DATA);
spin_unlock_bh(&d->tcf_lock);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
return 0;
}
static const struct nla_policy simple_policy[TCA_DEF_MAX + 1] = {
[TCA_DEF_PARMS] = { .len = sizeof(struct tc_defact) },
[TCA_DEF_DATA] = { .type = NLA_STRING, .len = SIMP_MAX_DATA },
};
static int tcf_simp_init(struct net *net, struct nlattr *nla,
struct nlattr *est, struct tc_action **a,
int ovr, int bind, bool rtnl_held,
struct tcf_proto *tp, struct netlink_ext_ack *extack)
{
struct tc_action_net *tn = net_generic(net, simp_net_id);
struct nlattr *tb[TCA_DEF_MAX + 1];
struct tcf_chain *goto_ch = NULL;
struct tc_defact *parm;
struct tcf_defact *d;
bool exists = false;
int ret = 0, err;
u32 index;
if (nla == NULL)
return -EINVAL;
err = nla_parse_nested_deprecated(tb, TCA_DEF_MAX, nla, simple_policy,
NULL);
if (err < 0)
return err;
if (tb[TCA_DEF_PARMS] == NULL)
return -EINVAL;
parm = nla_data(tb[TCA_DEF_PARMS]);
index = parm->index;
err = tcf_idr_check_alloc(tn, &index, a, bind);
if (err < 0)
return err;
exists = err;
if (exists && bind)
return 0;
if (tb[TCA_DEF_DATA] == NULL) {
if (exists)
tcf_idr_release(*a, bind);
else
tcf_idr_cleanup(tn, index);
return -EINVAL;
}
if (!exists) {
ret = tcf_idr_create(tn, index, est, a,
&act_simp_ops, bind, false);
if (ret) {
tcf_idr_cleanup(tn, index);
return ret;
}
d = to_defact(*a);
err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch,
extack);
if (err < 0)
goto release_idr;
err = alloc_defdata(d, tb[TCA_DEF_DATA]);
if (err < 0)
goto put_chain;
tcf_action_set_ctrlact(*a, parm->action, goto_ch);
ret = ACT_P_CREATED;
} else {
if (!ovr) {
err = -EEXIST;
goto release_idr;
}
err = reset_policy(*a, tb[TCA_DEF_DATA], parm, tp, extack);
if (err)
goto release_idr;
}
if (ret == ACT_P_CREATED)
tcf_idr_insert(tn, *a);
return ret;
put_chain:
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
release_idr:
tcf_idr_release(*a, bind);
return err;
}
static int tcf_simp_dump(struct sk_buff *skb, struct tc_action *a,
int bind, int ref)
{
unsigned char *b = skb_tail_pointer(skb);
struct tcf_defact *d = to_defact(a);
struct tc_defact opt = {
.index = d->tcf_index,
.refcnt = refcount_read(&d->tcf_refcnt) - ref,
.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
};
struct tcf_t t;
spin_lock_bh(&d->tcf_lock);
opt.action = d->tcf_action;
if (nla_put(skb, TCA_DEF_PARMS, sizeof(opt), &opt) ||
nla_put_string(skb, TCA_DEF_DATA, d->tcfd_defdata))
goto nla_put_failure;
tcf_tm_dump(&t, &d->tcf_tm);
if (nla_put_64bit(skb, TCA_DEF_TM, sizeof(t), &t, TCA_DEF_PAD))
goto nla_put_failure;
spin_unlock_bh(&d->tcf_lock);
return skb->len;
nla_put_failure:
spin_unlock_bh(&d->tcf_lock);
nlmsg_trim(skb, b);
return -1;
}
static int tcf_simp_walker(struct net *net, struct sk_buff *skb,
struct netlink_callback *cb, int type,
const struct tc_action_ops *ops,
struct netlink_ext_ack *extack)
{
struct tc_action_net *tn = net_generic(net, simp_net_id);
return tcf_generic_walker(tn, skb, cb, type, ops, extack);
}
static int tcf_simp_search(struct net *net, struct tc_action **a, u32 index)
{
struct tc_action_net *tn = net_generic(net, simp_net_id);
return tcf_idr_search(tn, a, index);
}
static struct tc_action_ops act_simp_ops = {
.kind = "simple",
.id = TCA_ID_SIMP,
.owner = THIS_MODULE,
.act = tcf_simp_act,
.dump = tcf_simp_dump,
.cleanup = tcf_simp_release,
.init = tcf_simp_init,
.walk = tcf_simp_walker,
.lookup = tcf_simp_search,
.size = sizeof(struct tcf_defact),
};
static __net_init int simp_init_net(struct net *net)
{
struct tc_action_net *tn = net_generic(net, simp_net_id);
return tc_action_net_init(tn, &act_simp_ops);
}
static void __net_exit simp_exit_net(struct list_head *net_list)
{
tc_action_net_exit(net_list, simp_net_id);
}
static struct pernet_operations simp_net_ops = {
.init = simp_init_net,
.exit_batch = simp_exit_net,
.id = &simp_net_id,
.size = sizeof(struct tc_action_net),
};
MODULE_AUTHOR("Jamal Hadi Salim(2005)");
MODULE_DESCRIPTION("Simple example action");
MODULE_LICENSE("GPL");
static int __init simp_init_module(void)
{
int ret = tcf_register_action(&act_simp_ops, &simp_net_ops);
if (!ret)
pr_info("Simple TC action Loaded\n");
return ret;
}
static void __exit simp_cleanup_module(void)
{
tcf_unregister_action(&act_simp_ops, &simp_net_ops);
}
module_init(simp_init_module);
module_exit(simp_cleanup_module);