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linux/net/sched/act_skbmod.c
Johannes Berg 8cb081746c netlink: make validation more configurable for future strictness 
We currently have two levels of strict validation:

 1) liberal (default)
     - undefined (type >= max) & NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted
     - garbage at end of message accepted
 2) strict (opt-in)
     - NLA_UNSPEC attributes accepted
     - attribute length >= expected accepted

Split out parsing strictness into four different options:
 * TRAILING     - check that there's no trailing data after parsing
                  attributes (in message or nested)
 * MAXTYPE      - reject attrs > max known type
 * UNSPEC       - reject attributes with NLA_UNSPEC policy entries
 * STRICT_ATTRS - strictly validate attribute size

The default for future things should be *everything*.
The current *_strict() is a combination of TRAILING and MAXTYPE,
and is renamed to _deprecated_strict().
The current regular parsing has none of this, and is renamed to
*_parse_deprecated().

Additionally it allows us to selectively set one of the new flags
even on old policies. Notably, the UNSPEC flag could be useful in
this case, since it can be arranged (by filling in the policy) to
not be an incompatible userspace ABI change, but would then going
forward prevent forgetting attribute entries. Similar can apply
to the POLICY flag.

We end up with the following renames:
 * nla_parse           -> nla_parse_deprecated
 * nla_parse_strict    -> nla_parse_deprecated_strict
 * nlmsg_parse         -> nlmsg_parse_deprecated
 * nlmsg_parse_strict  -> nlmsg_parse_deprecated_strict
 * nla_parse_nested    -> nla_parse_nested_deprecated
 * nla_validate_nested -> nla_validate_nested_deprecated

Using spatch, of course:
    @@
    expression TB, MAX, HEAD, LEN, POL, EXT;
    @@
    -nla_parse(TB, MAX, HEAD, LEN, POL, EXT)
    +nla_parse_deprecated(TB, MAX, HEAD, LEN, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, TB, MAX, POL, EXT;
    @@
    -nlmsg_parse_strict(NLH, HDRLEN, TB, MAX, POL, EXT)
    +nlmsg_parse_deprecated_strict(NLH, HDRLEN, TB, MAX, POL, EXT)

    @@
    expression TB, MAX, NLA, POL, EXT;
    @@
    -nla_parse_nested(TB, MAX, NLA, POL, EXT)
    +nla_parse_nested_deprecated(TB, MAX, NLA, POL, EXT)

    @@
    expression START, MAX, POL, EXT;
    @@
    -nla_validate_nested(START, MAX, POL, EXT)
    +nla_validate_nested_deprecated(START, MAX, POL, EXT)

    @@
    expression NLH, HDRLEN, MAX, POL, EXT;
    @@
    -nlmsg_validate(NLH, HDRLEN, MAX, POL, EXT)
    +nlmsg_validate_deprecated(NLH, HDRLEN, MAX, POL, EXT)

For this patch, don't actually add the strict, non-renamed versions
yet so that it breaks compile if I get it wrong.

Also, while at it, make nla_validate and nla_parse go down to a
common __nla_validate_parse() function to avoid code duplication.

Ultimately, this allows us to have very strict validation for every
new caller of nla_parse()/nlmsg_parse() etc as re-introduced in the
next patch, while existing things will continue to work as is.

In effect then, this adds fully strict validation for any new command.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-04-27 17:07:21 -04:00

324 lines
8.1 KiB
C
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/*
* net/sched/act_skbmod.c skb data modifier
*
* Copyright (c) 2016 Jamal Hadi Salim <jhs@mojatatu.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/module.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_skbmod.h>
#include <net/tc_act/tc_skbmod.h>
static unsigned int skbmod_net_id;
static struct tc_action_ops act_skbmod_ops;
#define MAX_EDIT_LEN ETH_HLEN
static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a,
struct tcf_result *res)
{
struct tcf_skbmod *d = to_skbmod(a);
int action;
struct tcf_skbmod_params *p;
u64 flags;
int err;
tcf_lastuse_update(&d->tcf_tm);
bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);
/* XXX: if you are going to edit more fields beyond ethernet header
* (example when you add IP header replacement or vlan swap)
* then MAX_EDIT_LEN needs to change appropriately
*/
err = skb_ensure_writable(skb, MAX_EDIT_LEN);
if (unlikely(err)) /* best policy is to drop on the floor */
goto drop;
action = READ_ONCE(d->tcf_action);
if (unlikely(action == TC_ACT_SHOT))
goto drop;
p = rcu_dereference_bh(d->skbmod_p);
flags = p->flags;
if (flags & SKBMOD_F_DMAC)
ether_addr_copy(eth_hdr(skb)->h_dest, p->eth_dst);
if (flags & SKBMOD_F_SMAC)
ether_addr_copy(eth_hdr(skb)->h_source, p->eth_src);
if (flags & SKBMOD_F_ETYPE)
eth_hdr(skb)->h_proto = p->eth_type;
if (flags & SKBMOD_F_SWAPMAC) {
u16 tmpaddr[ETH_ALEN / 2]; /* ether_addr_copy() requirement */
/*XXX: I am sure we can come up with more efficient swapping*/
ether_addr_copy((u8 *)tmpaddr, eth_hdr(skb)->h_dest);
ether_addr_copy(eth_hdr(skb)->h_dest, eth_hdr(skb)->h_source);
ether_addr_copy(eth_hdr(skb)->h_source, (u8 *)tmpaddr);
}
return action;
drop:
qstats_overlimit_inc(this_cpu_ptr(d->common.cpu_qstats));
return TC_ACT_SHOT;
}
static const struct nla_policy skbmod_policy[TCA_SKBMOD_MAX + 1] = {
[TCA_SKBMOD_PARMS] = { .len = sizeof(struct tc_skbmod) },
[TCA_SKBMOD_DMAC] = { .len = ETH_ALEN },
[TCA_SKBMOD_SMAC] = { .len = ETH_ALEN },
[TCA_SKBMOD_ETYPE] = { .type = NLA_U16 },
};
static int tcf_skbmod_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, skbmod_net_id);
struct nlattr *tb[TCA_SKBMOD_MAX + 1];
struct tcf_skbmod_params *p, *p_old;
struct tcf_chain *goto_ch = NULL;
struct tc_skbmod *parm;
struct tcf_skbmod *d;
bool exists = false;
u8 *daddr = NULL;
u8 *saddr = NULL;
u16 eth_type = 0;
u32 lflags = 0;
int ret = 0, err;
if (!nla)
return -EINVAL;
err = nla_parse_nested_deprecated(tb, TCA_SKBMOD_MAX, nla,
skbmod_policy, NULL);
if (err < 0)
return err;
if (!tb[TCA_SKBMOD_PARMS])
return -EINVAL;
if (tb[TCA_SKBMOD_DMAC]) {
daddr = nla_data(tb[TCA_SKBMOD_DMAC]);
lflags |= SKBMOD_F_DMAC;
}
if (tb[TCA_SKBMOD_SMAC]) {
saddr = nla_data(tb[TCA_SKBMOD_SMAC]);
lflags |= SKBMOD_F_SMAC;
}
if (tb[TCA_SKBMOD_ETYPE]) {
eth_type = nla_get_u16(tb[TCA_SKBMOD_ETYPE]);
lflags |= SKBMOD_F_ETYPE;
}
parm = nla_data(tb[TCA_SKBMOD_PARMS]);
if (parm->flags & SKBMOD_F_SWAPMAC)
lflags = SKBMOD_F_SWAPMAC;
err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
if (err < 0)
return err;
exists = err;
if (exists && bind)
return 0;
if (!lflags) {
if (exists)
tcf_idr_release(*a, bind);
else
tcf_idr_cleanup(tn, parm->index);
return -EINVAL;
}
if (!exists) {
ret = tcf_idr_create(tn, parm->index, est, a,
&act_skbmod_ops, bind, true);
if (ret) {
tcf_idr_cleanup(tn, parm->index);
return ret;
}
ret = ACT_P_CREATED;
} else if (!ovr) {
tcf_idr_release(*a, bind);
return -EEXIST;
}
err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
if (err < 0)
goto release_idr;
d = to_skbmod(*a);
p = kzalloc(sizeof(struct tcf_skbmod_params), GFP_KERNEL);
if (unlikely(!p)) {
err = -ENOMEM;
goto put_chain;
}
p->flags = lflags;
if (ovr)
spin_lock_bh(&d->tcf_lock);
/* Protected by tcf_lock if overwriting existing action. */
goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
p_old = rcu_dereference_protected(d->skbmod_p, 1);
if (lflags & SKBMOD_F_DMAC)
ether_addr_copy(p->eth_dst, daddr);
if (lflags & SKBMOD_F_SMAC)
ether_addr_copy(p->eth_src, saddr);
if (lflags & SKBMOD_F_ETYPE)
p->eth_type = htons(eth_type);
rcu_assign_pointer(d->skbmod_p, p);
if (ovr)
spin_unlock_bh(&d->tcf_lock);
if (p_old)
kfree_rcu(p_old, rcu);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
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 void tcf_skbmod_cleanup(struct tc_action *a)
{
struct tcf_skbmod *d = to_skbmod(a);
struct tcf_skbmod_params *p;
p = rcu_dereference_protected(d->skbmod_p, 1);
if (p)
kfree_rcu(p, rcu);
}
static int tcf_skbmod_dump(struct sk_buff *skb, struct tc_action *a,
int bind, int ref)
{
struct tcf_skbmod *d = to_skbmod(a);
unsigned char *b = skb_tail_pointer(skb);
struct tcf_skbmod_params *p;
struct tc_skbmod 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;
p = rcu_dereference_protected(d->skbmod_p,
lockdep_is_held(&d->tcf_lock));
opt.flags = p->flags;
if (nla_put(skb, TCA_SKBMOD_PARMS, sizeof(opt), &opt))
goto nla_put_failure;
if ((p->flags & SKBMOD_F_DMAC) &&
nla_put(skb, TCA_SKBMOD_DMAC, ETH_ALEN, p->eth_dst))
goto nla_put_failure;
if ((p->flags & SKBMOD_F_SMAC) &&
nla_put(skb, TCA_SKBMOD_SMAC, ETH_ALEN, p->eth_src))
goto nla_put_failure;
if ((p->flags & SKBMOD_F_ETYPE) &&
nla_put_u16(skb, TCA_SKBMOD_ETYPE, ntohs(p->eth_type)))
goto nla_put_failure;
tcf_tm_dump(&t, &d->tcf_tm);
if (nla_put_64bit(skb, TCA_SKBMOD_TM, sizeof(t), &t, TCA_SKBMOD_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_skbmod_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, skbmod_net_id);
return tcf_generic_walker(tn, skb, cb, type, ops, extack);
}
static int tcf_skbmod_search(struct net *net, struct tc_action **a, u32 index)
{
struct tc_action_net *tn = net_generic(net, skbmod_net_id);
return tcf_idr_search(tn, a, index);
}
static struct tc_action_ops act_skbmod_ops = {
.kind = "skbmod",
.id = TCA_ACT_SKBMOD,
.owner = THIS_MODULE,
.act = tcf_skbmod_act,
.dump = tcf_skbmod_dump,
.init = tcf_skbmod_init,
.cleanup = tcf_skbmod_cleanup,
.walk = tcf_skbmod_walker,
.lookup = tcf_skbmod_search,
.size = sizeof(struct tcf_skbmod),
};
static __net_init int skbmod_init_net(struct net *net)
{
struct tc_action_net *tn = net_generic(net, skbmod_net_id);
return tc_action_net_init(tn, &act_skbmod_ops);
}
static void __net_exit skbmod_exit_net(struct list_head *net_list)
{
tc_action_net_exit(net_list, skbmod_net_id);
}
static struct pernet_operations skbmod_net_ops = {
.init = skbmod_init_net,
.exit_batch = skbmod_exit_net,
.id = &skbmod_net_id,
.size = sizeof(struct tc_action_net),
};
MODULE_AUTHOR("Jamal Hadi Salim, <jhs@mojatatu.com>");
MODULE_DESCRIPTION("SKB data mod-ing");
MODULE_LICENSE("GPL");
static int __init skbmod_init_module(void)
{
return tcf_register_action(&act_skbmod_ops, &skbmod_net_ops);
}
static void __exit skbmod_cleanup_module(void)
{
tcf_unregister_action(&act_skbmod_ops, &skbmod_net_ops);
}
module_init(skbmod_init_module);
module_exit(skbmod_cleanup_module);
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