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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (c) 2021 Red Hat GmbH
*
* Author: Florian Westphal <fw@strlen.de>
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/errno.h>
#include <linux/netlink.h>
#include <linux/slab.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_hook.h>
#include <net/netfilter/nf_tables.h>
#include <net/sock.h>
static const struct nla_policy nfnl_hook_nla_policy[NFNLA_HOOK_MAX + 1] = {
[NFNLA_HOOK_HOOKNUM] = { .type = NLA_U32 },
[NFNLA_HOOK_PRIORITY] = { .type = NLA_U32 },
[NFNLA_HOOK_DEV] = { .type = NLA_STRING,
.len = IFNAMSIZ - 1 },
[NFNLA_HOOK_FUNCTION_NAME] = { .type = NLA_NUL_STRING,
.len = KSYM_NAME_LEN, },
[NFNLA_HOOK_MODULE_NAME] = { .type = NLA_NUL_STRING,
.len = MODULE_NAME_LEN, },
[NFNLA_HOOK_CHAIN_INFO] = { .type = NLA_NESTED, },
};
static int nf_netlink_dump_start_rcu(struct sock *nlsk, struct sk_buff *skb,
const struct nlmsghdr *nlh,
struct netlink_dump_control *c)
{
int err;
if (!try_module_get(THIS_MODULE))
return -EINVAL;
rcu_read_unlock();
err = netlink_dump_start(nlsk, skb, nlh, c);
rcu_read_lock();
module_put(THIS_MODULE);
return err;
}
struct nfnl_dump_hook_data {
char devname[IFNAMSIZ];
unsigned long headv;
u8 hook;
};
static int nfnl_hook_put_nft_chain_info(struct sk_buff *nlskb,
const struct nfnl_dump_hook_data *ctx,
unsigned int seq,
const struct nf_hook_ops *ops)
{
struct net *net = sock_net(nlskb->sk);
struct nlattr *nest, *nest2;
struct nft_chain *chain;
int ret = 0;
if (ops->hook_ops_type != NF_HOOK_OP_NF_TABLES)
return 0;
chain = ops->priv;
if (WARN_ON_ONCE(!chain))
return 0;
if (!nft_is_active(net, chain))
return 0;
nest = nla_nest_start(nlskb, NFNLA_HOOK_CHAIN_INFO);
if (!nest)
return -EMSGSIZE;
ret = nla_put_be32(nlskb, NFNLA_HOOK_INFO_TYPE,
htonl(NFNL_HOOK_TYPE_NFTABLES));
if (ret)
goto cancel_nest;
nest2 = nla_nest_start(nlskb, NFNLA_HOOK_INFO_DESC);
if (!nest2)
goto cancel_nest;
ret = nla_put_string(nlskb, NFNLA_CHAIN_TABLE, chain->table->name);
if (ret)
goto cancel_nest;
ret = nla_put_string(nlskb, NFNLA_CHAIN_NAME, chain->name);
if (ret)
goto cancel_nest;
ret = nla_put_u8(nlskb, NFNLA_CHAIN_FAMILY, chain->table->family);
if (ret)
goto cancel_nest;
nla_nest_end(nlskb, nest2);
nla_nest_end(nlskb, nest);
return ret;
cancel_nest:
nla_nest_cancel(nlskb, nest);
return -EMSGSIZE;
}
static int nfnl_hook_dump_one(struct sk_buff *nlskb,
const struct nfnl_dump_hook_data *ctx,
const struct nf_hook_ops *ops,
unsigned int seq)
{
u16 event = nfnl_msg_type(NFNL_SUBSYS_HOOK, NFNL_MSG_HOOK_GET);
unsigned int portid = NETLINK_CB(nlskb).portid;
struct nlmsghdr *nlh;
int ret = -EMSGSIZE;
#ifdef CONFIG_KALLSYMS
char sym[KSYM_SYMBOL_LEN];
char *module_name;
#endif
nlh = nfnl_msg_put(nlskb, portid, seq, event,
NLM_F_MULTI, ops->pf, NFNETLINK_V0, 0);
if (!nlh)
goto nla_put_failure;
#ifdef CONFIG_KALLSYMS
ret = snprintf(sym, sizeof(sym), "%ps", ops->hook);
if (ret >= sizeof(sym)) {
ret = -EINVAL;
goto nla_put_failure;
}
module_name = strstr(sym, " [");
if (module_name) {
char *end;
*module_name = '\0';
module_name += 2;
end = strchr(module_name, ']');
if (end) {
*end = 0;
ret = nla_put_string(nlskb, NFNLA_HOOK_MODULE_NAME, module_name);
if (ret)
goto nla_put_failure;
}
}
ret = nla_put_string(nlskb, NFNLA_HOOK_FUNCTION_NAME, sym);
if (ret)
goto nla_put_failure;
#endif
ret = nla_put_be32(nlskb, NFNLA_HOOK_HOOKNUM, htonl(ops->hooknum));
if (ret)
goto nla_put_failure;
ret = nla_put_be32(nlskb, NFNLA_HOOK_PRIORITY, htonl(ops->priority));
if (ret)
goto nla_put_failure;
ret = nfnl_hook_put_nft_chain_info(nlskb, ctx, seq, ops);
if (ret)
goto nla_put_failure;
nlmsg_end(nlskb, nlh);
return 0;
nla_put_failure:
nlmsg_trim(nlskb, nlh);
return ret;
}
static const struct nf_hook_entries *
nfnl_hook_entries_head(u8 pf, unsigned int hook, struct net *net, const char *dev)
{
const struct nf_hook_entries *hook_head = NULL;
#ifdef CONFIG_NETFILTER_INGRESS
struct net_device *netdev;
#endif
switch (pf) {
case NFPROTO_IPV4:
if (hook >= ARRAY_SIZE(net->nf.hooks_ipv4))
return ERR_PTR(-EINVAL);
hook_head = rcu_dereference(net->nf.hooks_ipv4[hook]);
break;
case NFPROTO_IPV6:
if (hook >= ARRAY_SIZE(net->nf.hooks_ipv6))
return ERR_PTR(-EINVAL);
hook_head = rcu_dereference(net->nf.hooks_ipv6[hook]);
break;
case NFPROTO_ARP:
#ifdef CONFIG_NETFILTER_FAMILY_ARP
if (hook >= ARRAY_SIZE(net->nf.hooks_arp))
return ERR_PTR(-EINVAL);
hook_head = rcu_dereference(net->nf.hooks_arp[hook]);
#endif
break;
case NFPROTO_BRIDGE:
#ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
if (hook >= ARRAY_SIZE(net->nf.hooks_bridge))
return ERR_PTR(-EINVAL);
hook_head = rcu_dereference(net->nf.hooks_bridge[hook]);
#endif
break;
#if IS_ENABLED(CONFIG_DECNET)
case NFPROTO_DECNET:
if (hook >= ARRAY_SIZE(net->nf.hooks_decnet))
return ERR_PTR(-EINVAL);
hook_head = rcu_dereference(net->nf.hooks_decnet[hook]);
break;
#endif
#ifdef CONFIG_NETFILTER_INGRESS
case NFPROTO_NETDEV:
if (hook != NF_NETDEV_INGRESS)
return ERR_PTR(-EOPNOTSUPP);
if (!dev)
return ERR_PTR(-ENODEV);
netdev = dev_get_by_name_rcu(net, dev);
if (!netdev)
return ERR_PTR(-ENODEV);
return rcu_dereference(netdev->nf_hooks_ingress);
#endif
default:
return ERR_PTR(-EPROTONOSUPPORT);
}
return hook_head;
}
static int nfnl_hook_dump(struct sk_buff *nlskb,
struct netlink_callback *cb)
{
struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
struct nfnl_dump_hook_data *ctx = cb->data;
int err, family = nfmsg->nfgen_family;
struct net *net = sock_net(nlskb->sk);
struct nf_hook_ops * const *ops;
const struct nf_hook_entries *e;
unsigned int i = cb->args[0];
rcu_read_lock();
e = nfnl_hook_entries_head(family, ctx->hook, net, ctx->devname);
if (!e)
goto done;
if (IS_ERR(e)) {
cb->seq++;
goto done;
}
if ((unsigned long)e != ctx->headv || i >= e->num_hook_entries)
cb->seq++;
ops = nf_hook_entries_get_hook_ops(e);
for (; i < e->num_hook_entries; i++) {
err = nfnl_hook_dump_one(nlskb, ctx, ops[i],
cb->nlh->nlmsg_seq);
if (err)
break;
}
done:
nl_dump_check_consistent(cb, nlmsg_hdr(nlskb));
rcu_read_unlock();
cb->args[0] = i;
return nlskb->len;
}
static int nfnl_hook_dump_start(struct netlink_callback *cb)
{
const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
const struct nlattr * const *nla = cb->data;
struct nfnl_dump_hook_data *ctx = NULL;
struct net *net = sock_net(cb->skb->sk);
u8 family = nfmsg->nfgen_family;
char name[IFNAMSIZ] = "";
const void *head;
u32 hooknum;
hooknum = ntohl(nla_get_be32(nla[NFNLA_HOOK_HOOKNUM]));
if (hooknum > 255)
return -EINVAL;
if (family == NFPROTO_NETDEV) {
if (!nla[NFNLA_HOOK_DEV])
return -EINVAL;
nla_strscpy(name, nla[NFNLA_HOOK_DEV], sizeof(name));
}
rcu_read_lock();
/* Not dereferenced; for consistency check only */
head = nfnl_hook_entries_head(family, hooknum, net, name);
rcu_read_unlock();
if (head && IS_ERR(head))
return PTR_ERR(head);
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
strscpy(ctx->devname, name, sizeof(ctx->devname));
ctx->headv = (unsigned long)head;
ctx->hook = hooknum;
cb->seq = 1;
cb->data = ctx;
return 0;
}
static int nfnl_hook_dump_stop(struct netlink_callback *cb)
{
kfree(cb->data);
return 0;
}
static int nfnl_hook_get(struct sk_buff *skb,
const struct nfnl_info *info,
const struct nlattr * const nla[])
{
if (!nla[NFNLA_HOOK_HOOKNUM])
return -EINVAL;
if (info->nlh->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
.start = nfnl_hook_dump_start,
.done = nfnl_hook_dump_stop,
.dump = nfnl_hook_dump,
.module = THIS_MODULE,
.data = (void *)nla,
};
return nf_netlink_dump_start_rcu(info->sk, skb, info->nlh, &c);
}
return -EOPNOTSUPP;
}
static const struct nfnl_callback nfnl_hook_cb[NFNL_MSG_HOOK_MAX] = {
[NFNL_MSG_HOOK_GET] = {
.call = nfnl_hook_get,
.type = NFNL_CB_RCU,
.attr_count = NFNLA_HOOK_MAX,
.policy = nfnl_hook_nla_policy
},
};
static const struct nfnetlink_subsystem nfhook_subsys = {
.name = "nfhook",
.subsys_id = NFNL_SUBSYS_HOOK,
.cb_count = NFNL_MSG_HOOK_MAX,
.cb = nfnl_hook_cb,
};
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_HOOK);
static int __init nfnetlink_hook_init(void)
{
return nfnetlink_subsys_register(&nfhook_subsys);
}
static void __exit nfnetlink_hook_exit(void)
{
nfnetlink_subsys_unregister(&nfhook_subsys);
}
module_init(nfnetlink_hook_init);
module_exit(nfnetlink_hook_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
MODULE_DESCRIPTION("nfnetlink_hook: list registered netfilter hooks");
|