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linux-next/net/netfilter/nfnetlink.c
Florian Westphal 71ad00c50d netfilter: nf_tables: fix module unload race 
We must first remove the nfnetlink protocol handler when nf_tables module
is unloaded -- we don't want userspace to submit new change requests once
we've started to tear down nft state.

Furthermore, nfnetlink must not call any subsystem function after
call_batch returned -EAGAIN.

EAGAIN means the subsys mutex was dropped, so its unlikely but possible that
nf_tables subsystem was removed due to 'rmmod nf_tables' on another cpu.

Therefore, we must abort batch completely and not move on to next part of
the batch.

Last, we can't invoke ->abort unless we've checked that the subsystem is
still registered.

Change netns exit path of nf_tables to make sure any incompleted
transaction gets removed on exit.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
2018-06-12 19:28:18 +02:00

632 lines
15 KiB
C
Raw Blame History

/* Netfilter messages via netlink socket. Allows for user space
* protocol helpers and general trouble making from userspace.
*
* (C) 2001 by Jay Schulist <jschlst@samba.org>,
* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
* (C) 2005-2017 by Pablo Neira Ayuso <pablo@netfilter.org>
*
* Initial netfilter messages via netlink development funded and
* generally made possible by Network Robots, Inc. (www.networkrobots.com)
*
* Further development of this code funded by Astaro AG (http://www.astaro.com)
*
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/uaccess.h>
#include <net/sock.h>
#include <linux/init.h>
#include <linux/sched/signal.h>
#include <net/netlink.h>
#include <linux/netfilter/nfnetlink.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
#define nfnl_dereference_protected(id) \
rcu_dereference_protected(table[(id)].subsys, \
lockdep_nfnl_is_held((id)))
#define NFNL_MAX_ATTR_COUNT 32
static struct {
struct mutex mutex;
const struct nfnetlink_subsystem __rcu *subsys;
} table[NFNL_SUBSYS_COUNT];
static const int nfnl_group2type[NFNLGRP_MAX+1] = {
[NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK,
[NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK,
[NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK,
[NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP,
[NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP,
[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
[NFNLGRP_NFTABLES] = NFNL_SUBSYS_NFTABLES,
[NFNLGRP_ACCT_QUOTA] = NFNL_SUBSYS_ACCT,
[NFNLGRP_NFTRACE] = NFNL_SUBSYS_NFTABLES,
};
void nfnl_lock(__u8 subsys_id)
{
mutex_lock(&table[subsys_id].mutex);
}
EXPORT_SYMBOL_GPL(nfnl_lock);
void nfnl_unlock(__u8 subsys_id)
{
mutex_unlock(&table[subsys_id].mutex);
}
EXPORT_SYMBOL_GPL(nfnl_unlock);
#ifdef CONFIG_PROVE_LOCKING
bool lockdep_nfnl_is_held(u8 subsys_id)
{
return lockdep_is_held(&table[subsys_id].mutex);
}
EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
#endif
int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
{
u8 cb_id;
/* Sanity-check attr_count size to avoid stack buffer overflow. */
for (cb_id = 0; cb_id < n->cb_count; cb_id++)
if (WARN_ON(n->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT))
return -EINVAL;
nfnl_lock(n->subsys_id);
if (table[n->subsys_id].subsys) {
nfnl_unlock(n->subsys_id);
return -EBUSY;
}
rcu_assign_pointer(table[n->subsys_id].subsys, n);
nfnl_unlock(n->subsys_id);
return 0;
}
EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
{
nfnl_lock(n->subsys_id);
table[n->subsys_id].subsys = NULL;
nfnl_unlock(n->subsys_id);
synchronize_rcu();
return 0;
}
EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u16 type)
{
u8 subsys_id = NFNL_SUBSYS_ID(type);
if (subsys_id >= NFNL_SUBSYS_COUNT)
return NULL;
return rcu_dereference(table[subsys_id].subsys);
}
static inline const struct nfnl_callback *
nfnetlink_find_client(u16 type, const struct nfnetlink_subsystem *ss)
{
u8 cb_id = NFNL_MSG_TYPE(type);
if (cb_id >= ss->cb_count)
return NULL;
return &ss->cb[cb_id];
}
int nfnetlink_has_listeners(struct net *net, unsigned int group)
{
return netlink_has_listeners(net->nfnl, group);
}
EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
unsigned int group, int echo, gfp_t flags)
{
return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
}
EXPORT_SYMBOL_GPL(nfnetlink_send);
int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
{
return netlink_set_err(net->nfnl, portid, group, error);
}
EXPORT_SYMBOL_GPL(nfnetlink_set_err);
int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
int flags)
{
return netlink_unicast(net->nfnl, skb, portid, flags);
}
EXPORT_SYMBOL_GPL(nfnetlink_unicast);
/* Process one complete nfnetlink message. */
static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
const struct nfnl_callback *nc;
const struct nfnetlink_subsystem *ss;
int type, err;
/* All the messages must at least contain nfgenmsg */
if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
return 0;
type = nlh->nlmsg_type;
replay:
rcu_read_lock();
ss = nfnetlink_get_subsys(type);
if (!ss) {
#ifdef CONFIG_MODULES
rcu_read_unlock();
request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
rcu_read_lock();
ss = nfnetlink_get_subsys(type);
if (!ss)
#endif
{
rcu_read_unlock();
return -EINVAL;
}
}
nc = nfnetlink_find_client(type, ss);
if (!nc) {
rcu_read_unlock();
return -EINVAL;
}
{
int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
struct nlattr *attr = (void *)nlh + min_len;
int attrlen = nlh->nlmsg_len - min_len;
__u8 subsys_id = NFNL_SUBSYS_ID(type);
/* Sanity-check NFNL_MAX_ATTR_COUNT */
if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
rcu_read_unlock();
return -ENOMEM;
}
err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen,
ss->cb[cb_id].policy, extack);
if (err < 0) {
rcu_read_unlock();
return err;
}
if (nc->call_rcu) {
err = nc->call_rcu(net, net->nfnl, skb, nlh,
(const struct nlattr **)cda,
extack);
rcu_read_unlock();
} else {
rcu_read_unlock();
nfnl_lock(subsys_id);
if (nfnl_dereference_protected(subsys_id) != ss ||
nfnetlink_find_client(type, ss) != nc)
err = -EAGAIN;
else if (nc->call)
err = nc->call(net, net->nfnl, skb, nlh,
(const struct nlattr **)cda,
extack);
else
err = -EINVAL;
nfnl_unlock(subsys_id);
}
if (err == -EAGAIN)
goto replay;
return err;
}
}
struct nfnl_err {
struct list_head head;
struct nlmsghdr *nlh;
int err;
struct netlink_ext_ack extack;
};
static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err,
const struct netlink_ext_ack *extack)
{
struct nfnl_err *nfnl_err;
nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
if (nfnl_err == NULL)
return -ENOMEM;
nfnl_err->nlh = nlh;
nfnl_err->err = err;
nfnl_err->extack = *extack;
list_add_tail(&nfnl_err->head, list);
return 0;
}
static void nfnl_err_del(struct nfnl_err *nfnl_err)
{
list_del(&nfnl_err->head);
kfree(nfnl_err);
}
static void nfnl_err_reset(struct list_head *err_list)
{
struct nfnl_err *nfnl_err, *next;
list_for_each_entry_safe(nfnl_err, next, err_list, head)
nfnl_err_del(nfnl_err);
}
static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
{
struct nfnl_err *nfnl_err, *next;
list_for_each_entry_safe(nfnl_err, next, err_list, head) {
netlink_ack(skb, nfnl_err->nlh, nfnl_err->err,
&nfnl_err->extack);
nfnl_err_del(nfnl_err);
}
}
enum {
NFNL_BATCH_FAILURE = (1 << 0),
NFNL_BATCH_DONE = (1 << 1),
NFNL_BATCH_REPLAY = (1 << 2),
};
static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
u16 subsys_id, u32 genid)
{
struct sk_buff *oskb = skb;
struct net *net = sock_net(skb->sk);
const struct nfnetlink_subsystem *ss;
const struct nfnl_callback *nc;
struct netlink_ext_ack extack;
LIST_HEAD(err_list);
u32 status;
int err;
if (subsys_id >= NFNL_SUBSYS_COUNT)
return netlink_ack(skb, nlh, -EINVAL, NULL);
replay:
status = 0;
skb = netlink_skb_clone(oskb, GFP_KERNEL);
if (!skb)
return netlink_ack(oskb, nlh, -ENOMEM, NULL);
nfnl_lock(subsys_id);
ss = nfnl_dereference_protected(subsys_id);
if (!ss) {
#ifdef CONFIG_MODULES
nfnl_unlock(subsys_id);
request_module("nfnetlink-subsys-%d", subsys_id);
nfnl_lock(subsys_id);
ss = nfnl_dereference_protected(subsys_id);
if (!ss)
#endif
{
nfnl_unlock(subsys_id);
netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
return kfree_skb(skb);
}
}
if (!ss->commit || !ss->abort) {
nfnl_unlock(subsys_id);
netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
return kfree_skb(skb);
}
if (genid && ss->valid_genid && !ss->valid_genid(net, genid)) {
nfnl_unlock(subsys_id);
netlink_ack(oskb, nlh, -ERESTART, NULL);
return kfree_skb(skb);
}
while (skb->len >= nlmsg_total_size(0)) {
int msglen, type;
if (fatal_signal_pending(current)) {
nfnl_err_reset(&err_list);
err = -EINTR;
status = NFNL_BATCH_FAILURE;
goto done;
}
memset(&extack, 0, sizeof(extack));
nlh = nlmsg_hdr(skb);
err = 0;
if (nlh->nlmsg_len < NLMSG_HDRLEN ||
skb->len < nlh->nlmsg_len ||
nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
nfnl_err_reset(&err_list);
status |= NFNL_BATCH_FAILURE;
goto done;
}
/* Only requests are handled by the kernel */
if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
err = -EINVAL;
goto ack;
}
type = nlh->nlmsg_type;
if (type == NFNL_MSG_BATCH_BEGIN) {
/* Malformed: Batch begin twice */
nfnl_err_reset(&err_list);
status |= NFNL_BATCH_FAILURE;
goto done;
} else if (type == NFNL_MSG_BATCH_END) {
status |= NFNL_BATCH_DONE;
goto done;
} else if (type < NLMSG_MIN_TYPE) {
err = -EINVAL;
goto ack;
}
/* We only accept a batch with messages for the same
* subsystem.
*/
if (NFNL_SUBSYS_ID(type) != subsys_id) {
err = -EINVAL;
goto ack;
}
nc = nfnetlink_find_client(type, ss);
if (!nc) {
err = -EINVAL;
goto ack;
}
{
int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
struct nlattr *attr = (void *)nlh + min_len;
int attrlen = nlh->nlmsg_len - min_len;
/* Sanity-check NFTA_MAX_ATTR */
if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
err = -ENOMEM;
goto ack;
}
err = nla_parse(cda, ss->cb[cb_id].attr_count, attr,
attrlen, ss->cb[cb_id].policy, NULL);
if (err < 0)
goto ack;
if (nc->call_batch) {
err = nc->call_batch(net, net->nfnl, skb, nlh,
(const struct nlattr **)cda,
&extack);
}
/* The lock was released to autoload some module, we
* have to abort and start from scratch using the
* original skb.
*/
if (err == -EAGAIN) {
status |= NFNL_BATCH_REPLAY;
goto done;
}
}
ack:
if (nlh->nlmsg_flags & NLM_F_ACK || err) {
/* Errors are delivered once the full batch has been
* processed, this avoids that the same error is
* reported several times when replaying the batch.
*/
if (nfnl_err_add(&err_list, nlh, err, &extack) < 0) {
/* We failed to enqueue an error, reset the
* list of errors and send OOM to userspace
* pointing to the batch header.
*/
nfnl_err_reset(&err_list);
netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
NULL);
status |= NFNL_BATCH_FAILURE;
goto done;
}
/* We don't stop processing the batch on errors, thus,
* userspace gets all the errors that the batch
* triggers.
*/
if (err)
status |= NFNL_BATCH_FAILURE;
}
msglen = NLMSG_ALIGN(nlh->nlmsg_len);
if (msglen > skb->len)
msglen = skb->len;
skb_pull(skb, msglen);
}
done:
if (status & NFNL_BATCH_REPLAY) {
const struct nfnetlink_subsystem *ss2;
ss2 = nfnl_dereference_protected(subsys_id);
if (ss2 == ss)
ss->abort(net, oskb);
nfnl_err_reset(&err_list);
nfnl_unlock(subsys_id);
kfree_skb(skb);
goto replay;
} else if (status == NFNL_BATCH_DONE) {
err = ss->commit(net, oskb);
if (err == -EAGAIN) {
status |= NFNL_BATCH_REPLAY;
goto done;
} else if (err) {
ss->abort(net, oskb);
netlink_ack(oskb, nlmsg_hdr(oskb), err, NULL);
}
} else {
ss->abort(net, oskb);
}
if (ss->cleanup)
ss->cleanup(net);
nfnl_err_deliver(&err_list, oskb);
nfnl_unlock(subsys_id);
kfree_skb(skb);
}
static const struct nla_policy nfnl_batch_policy[NFNL_BATCH_MAX + 1] = {
[NFNL_BATCH_GENID] = { .type = NLA_U32 },
};
static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
{
int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
struct nlattr *attr = (void *)nlh + min_len;
struct nlattr *cda[NFNL_BATCH_MAX + 1];
int attrlen = nlh->nlmsg_len - min_len;
struct nfgenmsg *nfgenmsg;
int msglen, err;
u32 gen_id = 0;
u16 res_id;
msglen = NLMSG_ALIGN(nlh->nlmsg_len);
if (msglen > skb->len)
msglen = skb->len;
if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
return;
err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,
NULL);
if (err < 0) {
netlink_ack(skb, nlh, err, NULL);
return;
}
if (cda[NFNL_BATCH_GENID])
gen_id = ntohl(nla_get_be32(cda[NFNL_BATCH_GENID]));
nfgenmsg = nlmsg_data(nlh);
skb_pull(skb, msglen);
/* Work around old nft using host byte order */
if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
res_id = NFNL_SUBSYS_NFTABLES;
else
res_id = ntohs(nfgenmsg->res_id);
nfnetlink_rcv_batch(skb, nlh, res_id, gen_id);
}
static void nfnetlink_rcv(struct sk_buff *skb)
{
struct nlmsghdr *nlh = nlmsg_hdr(skb);
if (skb->len < NLMSG_HDRLEN ||
nlh->nlmsg_len < NLMSG_HDRLEN ||
skb->len < nlh->nlmsg_len)
return;
if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
netlink_ack(skb, nlh, -EPERM, NULL);
return;
}
if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN)
nfnetlink_rcv_skb_batch(skb, nlh);
else
netlink_rcv_skb(skb, nfnetlink_rcv_msg);
}
#ifdef CONFIG_MODULES
static int nfnetlink_bind(struct net *net, int group)
{
const struct nfnetlink_subsystem *ss;
int type;
if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
return 0;
type = nfnl_group2type[group];
rcu_read_lock();
ss = nfnetlink_get_subsys(type << 8);
rcu_read_unlock();
if (!ss)
request_module("nfnetlink-subsys-%d", type);
return 0;
}
#endif
static int __net_init nfnetlink_net_init(struct net *net)
{
struct sock *nfnl;
struct netlink_kernel_cfg cfg = {
.groups = NFNLGRP_MAX,
.input = nfnetlink_rcv,
#ifdef CONFIG_MODULES
.bind = nfnetlink_bind,
#endif
};
nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
if (!nfnl)
return -ENOMEM;
net->nfnl_stash = nfnl;
rcu_assign_pointer(net->nfnl, nfnl);
return 0;
}
static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
{
struct net *net;
list_for_each_entry(net, net_exit_list, exit_list)
RCU_INIT_POINTER(net->nfnl, NULL);
synchronize_net();
list_for_each_entry(net, net_exit_list, exit_list)
netlink_kernel_release(net->nfnl_stash);
}
static struct pernet_operations nfnetlink_net_ops = {
.init = nfnetlink_net_init,
.exit_batch = nfnetlink_net_exit_batch,
};
static int __init nfnetlink_init(void)
{
int i;
for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
for (i=0; i<NFNL_SUBSYS_COUNT; i++)
mutex_init(&table[i].mutex);
return register_pernet_subsys(&nfnetlink_net_ops);
}
static void __exit nfnetlink_exit(void)
{
unregister_pernet_subsys(&nfnetlink_net_ops);
}
module_init(nfnetlink_init);
module_exit(nfnetlink_exit);
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