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![Florian Westphal](/assets/img/avatar_default.png)
Thomas and Juliana report a deadlock when running: (rmmod nf_conntrack_netlink/xfrm_user) conntrack -e NEW -E & modprobe -v xfrm_user They provided following analysis: conntrack -e NEW -E netlink_bind() netlink_lock_table() -> increases "nl_table_users" nfnetlink_bind() # does not unlock the table as it's locked by netlink_bind() __request_module() call_usermodehelper_exec() This triggers "modprobe nf_conntrack_netlink" from kernel, netlink_bind() won't return until modprobe process is done. "modprobe xfrm_user": xfrm_user_init() register_pernet_subsys() -> grab pernet_ops_rwsem .. netlink_table_grab() calls schedule() as "nl_table_users" is non-zero so modprobe is blocked because netlink_bind() increased nl_table_users while also holding pernet_ops_rwsem. "modprobe nf_conntrack_netlink" runs and inits nf_conntrack_netlink: ctnetlink_init() register_pernet_subsys() -> blocks on "pernet_ops_rwsem" thanks to xfrm_user module both modprobe processes wait on one another -- neither can make progress. Switch netlink_bind() to "nowait" modprobe -- this releases the netlink table lock, which then allows both modprobe instances to complete. Reported-by: Thomas Jarosch <thomas.jarosch@intra2net.com> Reported-by: Juliana Rodrigueiro <juliana.rodrigueiro@intra2net.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
639 lines
15 KiB
C
639 lines
15 KiB
C
/* Netfilter messages via netlink socket. Allows for user space
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* protocol helpers and general trouble making from userspace.
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*
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* (C) 2001 by Jay Schulist <jschlst@samba.org>,
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* (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
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* (C) 2005-2017 by Pablo Neira Ayuso <pablo@netfilter.org>
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*
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* Initial netfilter messages via netlink development funded and
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* generally made possible by Network Robots, Inc. (www.networkrobots.com)
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*
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* Further development of this code funded by Astaro AG (http://www.astaro.com)
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*
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* This software may be used and distributed according to the terms
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* of the GNU General Public License, incorporated herein by reference.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/socket.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/sockios.h>
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#include <linux/net.h>
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#include <linux/skbuff.h>
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#include <linux/uaccess.h>
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#include <net/sock.h>
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#include <linux/init.h>
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#include <linux/sched/signal.h>
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#include <net/netlink.h>
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#include <linux/netfilter/nfnetlink.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
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MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
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#define nfnl_dereference_protected(id) \
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rcu_dereference_protected(table[(id)].subsys, \
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lockdep_nfnl_is_held((id)))
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#define NFNL_MAX_ATTR_COUNT 32
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static struct {
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struct mutex mutex;
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const struct nfnetlink_subsystem __rcu *subsys;
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} table[NFNL_SUBSYS_COUNT];
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static const int nfnl_group2type[NFNLGRP_MAX+1] = {
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[NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK,
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[NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK,
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[NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK,
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[NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP,
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[NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP,
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[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
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[NFNLGRP_NFTABLES] = NFNL_SUBSYS_NFTABLES,
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[NFNLGRP_ACCT_QUOTA] = NFNL_SUBSYS_ACCT,
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[NFNLGRP_NFTRACE] = NFNL_SUBSYS_NFTABLES,
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};
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void nfnl_lock(__u8 subsys_id)
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{
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mutex_lock(&table[subsys_id].mutex);
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}
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EXPORT_SYMBOL_GPL(nfnl_lock);
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void nfnl_unlock(__u8 subsys_id)
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{
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mutex_unlock(&table[subsys_id].mutex);
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}
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EXPORT_SYMBOL_GPL(nfnl_unlock);
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#ifdef CONFIG_PROVE_LOCKING
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bool lockdep_nfnl_is_held(u8 subsys_id)
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{
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return lockdep_is_held(&table[subsys_id].mutex);
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}
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EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
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#endif
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int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
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{
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u8 cb_id;
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/* Sanity-check attr_count size to avoid stack buffer overflow. */
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for (cb_id = 0; cb_id < n->cb_count; cb_id++)
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if (WARN_ON(n->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT))
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return -EINVAL;
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nfnl_lock(n->subsys_id);
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if (table[n->subsys_id].subsys) {
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nfnl_unlock(n->subsys_id);
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return -EBUSY;
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}
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rcu_assign_pointer(table[n->subsys_id].subsys, n);
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nfnl_unlock(n->subsys_id);
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
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int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
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{
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nfnl_lock(n->subsys_id);
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table[n->subsys_id].subsys = NULL;
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nfnl_unlock(n->subsys_id);
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synchronize_rcu();
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return 0;
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}
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EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
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static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u16 type)
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{
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u8 subsys_id = NFNL_SUBSYS_ID(type);
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if (subsys_id >= NFNL_SUBSYS_COUNT)
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return NULL;
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return rcu_dereference(table[subsys_id].subsys);
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}
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static inline const struct nfnl_callback *
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nfnetlink_find_client(u16 type, const struct nfnetlink_subsystem *ss)
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{
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u8 cb_id = NFNL_MSG_TYPE(type);
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if (cb_id >= ss->cb_count)
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return NULL;
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return &ss->cb[cb_id];
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}
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int nfnetlink_has_listeners(struct net *net, unsigned int group)
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{
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return netlink_has_listeners(net->nfnl, group);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
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int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
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unsigned int group, int echo, gfp_t flags)
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{
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return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_send);
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int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
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{
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return netlink_set_err(net->nfnl, portid, group, error);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_set_err);
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int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
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int flags)
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{
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return netlink_unicast(net->nfnl, skb, portid, flags);
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}
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EXPORT_SYMBOL_GPL(nfnetlink_unicast);
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/* Process one complete nfnetlink message. */
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static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
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struct netlink_ext_ack *extack)
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{
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struct net *net = sock_net(skb->sk);
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const struct nfnl_callback *nc;
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const struct nfnetlink_subsystem *ss;
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int type, err;
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/* All the messages must at least contain nfgenmsg */
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if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
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return 0;
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type = nlh->nlmsg_type;
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replay:
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rcu_read_lock();
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ss = nfnetlink_get_subsys(type);
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if (!ss) {
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#ifdef CONFIG_MODULES
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rcu_read_unlock();
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request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
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rcu_read_lock();
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ss = nfnetlink_get_subsys(type);
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if (!ss)
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#endif
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{
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rcu_read_unlock();
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return -EINVAL;
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}
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}
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nc = nfnetlink_find_client(type, ss);
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if (!nc) {
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rcu_read_unlock();
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return -EINVAL;
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}
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{
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int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
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u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
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struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
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struct nlattr *attr = (void *)nlh + min_len;
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int attrlen = nlh->nlmsg_len - min_len;
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__u8 subsys_id = NFNL_SUBSYS_ID(type);
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/* Sanity-check NFNL_MAX_ATTR_COUNT */
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if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
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rcu_read_unlock();
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return -ENOMEM;
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}
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err = nla_parse_deprecated(cda, ss->cb[cb_id].attr_count,
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attr, attrlen,
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ss->cb[cb_id].policy, extack);
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if (err < 0) {
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rcu_read_unlock();
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return err;
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}
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if (nc->call_rcu) {
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err = nc->call_rcu(net, net->nfnl, skb, nlh,
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(const struct nlattr **)cda,
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extack);
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rcu_read_unlock();
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} else {
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rcu_read_unlock();
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nfnl_lock(subsys_id);
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if (nfnl_dereference_protected(subsys_id) != ss ||
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nfnetlink_find_client(type, ss) != nc)
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err = -EAGAIN;
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else if (nc->call)
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err = nc->call(net, net->nfnl, skb, nlh,
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(const struct nlattr **)cda,
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extack);
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else
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err = -EINVAL;
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nfnl_unlock(subsys_id);
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}
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if (err == -EAGAIN)
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goto replay;
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return err;
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}
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}
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struct nfnl_err {
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struct list_head head;
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struct nlmsghdr *nlh;
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int err;
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struct netlink_ext_ack extack;
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};
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static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err,
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const struct netlink_ext_ack *extack)
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{
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struct nfnl_err *nfnl_err;
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nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
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if (nfnl_err == NULL)
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return -ENOMEM;
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nfnl_err->nlh = nlh;
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nfnl_err->err = err;
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nfnl_err->extack = *extack;
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list_add_tail(&nfnl_err->head, list);
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return 0;
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}
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static void nfnl_err_del(struct nfnl_err *nfnl_err)
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{
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list_del(&nfnl_err->head);
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kfree(nfnl_err);
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}
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static void nfnl_err_reset(struct list_head *err_list)
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{
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struct nfnl_err *nfnl_err, *next;
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list_for_each_entry_safe(nfnl_err, next, err_list, head)
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nfnl_err_del(nfnl_err);
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}
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static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
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{
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struct nfnl_err *nfnl_err, *next;
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list_for_each_entry_safe(nfnl_err, next, err_list, head) {
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netlink_ack(skb, nfnl_err->nlh, nfnl_err->err,
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&nfnl_err->extack);
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nfnl_err_del(nfnl_err);
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}
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}
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enum {
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NFNL_BATCH_FAILURE = (1 << 0),
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NFNL_BATCH_DONE = (1 << 1),
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NFNL_BATCH_REPLAY = (1 << 2),
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};
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static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
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u16 subsys_id, u32 genid)
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{
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struct sk_buff *oskb = skb;
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struct net *net = sock_net(skb->sk);
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const struct nfnetlink_subsystem *ss;
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const struct nfnl_callback *nc;
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struct netlink_ext_ack extack;
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LIST_HEAD(err_list);
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u32 status;
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int err;
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if (subsys_id >= NFNL_SUBSYS_COUNT)
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return netlink_ack(skb, nlh, -EINVAL, NULL);
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replay:
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status = 0;
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skb = netlink_skb_clone(oskb, GFP_KERNEL);
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if (!skb)
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return netlink_ack(oskb, nlh, -ENOMEM, NULL);
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nfnl_lock(subsys_id);
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ss = nfnl_dereference_protected(subsys_id);
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if (!ss) {
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#ifdef CONFIG_MODULES
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nfnl_unlock(subsys_id);
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request_module("nfnetlink-subsys-%d", subsys_id);
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nfnl_lock(subsys_id);
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ss = nfnl_dereference_protected(subsys_id);
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if (!ss)
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#endif
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{
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nfnl_unlock(subsys_id);
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netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
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return kfree_skb(skb);
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}
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}
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if (!ss->valid_genid || !ss->commit || !ss->abort) {
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nfnl_unlock(subsys_id);
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netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
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return kfree_skb(skb);
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}
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if (!try_module_get(ss->owner)) {
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nfnl_unlock(subsys_id);
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netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
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return kfree_skb(skb);
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}
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if (!ss->valid_genid(net, genid)) {
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module_put(ss->owner);
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nfnl_unlock(subsys_id);
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netlink_ack(oskb, nlh, -ERESTART, NULL);
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return kfree_skb(skb);
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}
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nfnl_unlock(subsys_id);
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while (skb->len >= nlmsg_total_size(0)) {
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int msglen, type;
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if (fatal_signal_pending(current)) {
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nfnl_err_reset(&err_list);
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err = -EINTR;
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status = NFNL_BATCH_FAILURE;
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goto done;
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}
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memset(&extack, 0, sizeof(extack));
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nlh = nlmsg_hdr(skb);
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err = 0;
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if (nlh->nlmsg_len < NLMSG_HDRLEN ||
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skb->len < nlh->nlmsg_len ||
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nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
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nfnl_err_reset(&err_list);
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status |= NFNL_BATCH_FAILURE;
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goto done;
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}
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/* Only requests are handled by the kernel */
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if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
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err = -EINVAL;
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goto ack;
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}
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type = nlh->nlmsg_type;
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if (type == NFNL_MSG_BATCH_BEGIN) {
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/* Malformed: Batch begin twice */
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nfnl_err_reset(&err_list);
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status |= NFNL_BATCH_FAILURE;
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goto done;
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} else if (type == NFNL_MSG_BATCH_END) {
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status |= NFNL_BATCH_DONE;
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goto done;
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} else if (type < NLMSG_MIN_TYPE) {
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err = -EINVAL;
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goto ack;
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}
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/* We only accept a batch with messages for the same
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* subsystem.
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*/
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if (NFNL_SUBSYS_ID(type) != subsys_id) {
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err = -EINVAL;
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goto ack;
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}
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nc = nfnetlink_find_client(type, ss);
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if (!nc) {
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err = -EINVAL;
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goto ack;
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}
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{
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int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
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u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
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struct nlattr *cda[NFNL_MAX_ATTR_COUNT + 1];
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struct nlattr *attr = (void *)nlh + min_len;
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int attrlen = nlh->nlmsg_len - min_len;
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/* Sanity-check NFTA_MAX_ATTR */
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if (ss->cb[cb_id].attr_count > NFNL_MAX_ATTR_COUNT) {
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err = -ENOMEM;
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goto ack;
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}
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err = nla_parse_deprecated(cda,
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ss->cb[cb_id].attr_count,
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attr, attrlen,
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ss->cb[cb_id].policy, NULL);
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if (err < 0)
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goto ack;
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if (nc->call_batch) {
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err = nc->call_batch(net, net->nfnl, skb, nlh,
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(const struct nlattr **)cda,
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&extack);
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}
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/* The lock was released to autoload some module, we
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* have to abort and start from scratch using the
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* original skb.
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*/
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if (err == -EAGAIN) {
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status |= NFNL_BATCH_REPLAY;
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goto done;
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}
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}
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ack:
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if (nlh->nlmsg_flags & NLM_F_ACK || err) {
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/* Errors are delivered once the full batch has been
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* processed, this avoids that the same error is
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* reported several times when replaying the batch.
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*/
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if (nfnl_err_add(&err_list, nlh, err, &extack) < 0) {
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/* We failed to enqueue an error, reset the
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* list of errors and send OOM to userspace
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* pointing to the batch header.
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*/
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nfnl_err_reset(&err_list);
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netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
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NULL);
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status |= NFNL_BATCH_FAILURE;
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|
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) {
|
|
ss->abort(net, oskb);
|
|
nfnl_err_reset(&err_list);
|
|
kfree_skb(skb);
|
|
module_put(ss->owner);
|
|
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);
|
|
kfree_skb(skb);
|
|
module_put(ss->owner);
|
|
}
|
|
|
|
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_deprecated(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_nowait("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);
|