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https://github.com/torvalds/linux
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b53deef054
iptables/nftables has two types of log modules: 1. backend, e.g. nf_log_syslog, which implement the functionality 2. frontend, e.g. xt_LOG or nft_log, which call the functionality provided by backend based on nf_tables or xtables rule set. Problem is that the request_module() call to load the backed in nf_logger_find_get() might happen with nftables transaction mutex held in case the call path is via nf_tables/nft_compat. This can cause deadlocks (see 'Fixes' tags for details). The chosen solution as to let modprobe deal with this by adding 'pre: ' soft dep tag to xt_LOG (to load the syslog backend) and xt_NFLOG (to load nflog backend). Eric reports that this breaks on systems with older modprobe that doesn't support softdeps. Another, similar issue occurs when someone either insmods xt_(NF)LOG directly or unloads the backend module (possible if no log frontend is in use): because the frontend module is already loaded, modprobe is not invoked again so the softdep isn't evaluated. Add a workaround: If nf_logger_find_get() returns -ENOENT and call is not via nft_compat, load the backend explicitly and try again. Else, let nft_compat ask for deferred request_module via nf_tables infra. Softdeps are kept in-place, so with newer modprobe the dependencies are resolved from userspace. Fixes:cefa31a9d4("netfilter: nft_log: perform module load from nf_tables") Fixes:a38b5b56d6("netfilter: nf_log: add module softdeps") Reported-and-tested-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
91 lines
2.2 KiB
C
91 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (c) 2006 Patrick McHardy <kaber@trash.net>
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_NFLOG.h>
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#include <net/netfilter/nf_log.h>
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MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
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MODULE_DESCRIPTION("Xtables: packet logging to netlink using NFLOG");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("ipt_NFLOG");
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MODULE_ALIAS("ip6t_NFLOG");
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static unsigned int
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nflog_tg(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct xt_nflog_info *info = par->targinfo;
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struct net *net = xt_net(par);
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struct nf_loginfo li;
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li.type = NF_LOG_TYPE_ULOG;
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li.u.ulog.copy_len = info->len;
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li.u.ulog.group = info->group;
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li.u.ulog.qthreshold = info->threshold;
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li.u.ulog.flags = 0;
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if (info->flags & XT_NFLOG_F_COPY_LEN)
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li.u.ulog.flags |= NF_LOG_F_COPY_LEN;
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nf_log_packet(net, xt_family(par), xt_hooknum(par), skb, xt_in(par),
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xt_out(par), &li, "%s", info->prefix);
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return XT_CONTINUE;
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}
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static int nflog_tg_check(const struct xt_tgchk_param *par)
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{
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const struct xt_nflog_info *info = par->targinfo;
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int ret;
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if (info->flags & ~XT_NFLOG_MASK)
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return -EINVAL;
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if (info->prefix[sizeof(info->prefix) - 1] != '\0')
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return -EINVAL;
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ret = nf_logger_find_get(par->family, NF_LOG_TYPE_ULOG);
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if (ret != 0 && !par->nft_compat) {
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request_module("%s", "nfnetlink_log");
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ret = nf_logger_find_get(par->family, NF_LOG_TYPE_ULOG);
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}
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return ret;
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}
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static void nflog_tg_destroy(const struct xt_tgdtor_param *par)
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{
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nf_logger_put(par->family, NF_LOG_TYPE_ULOG);
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}
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static struct xt_target nflog_tg_reg __read_mostly = {
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.name = "NFLOG",
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.revision = 0,
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.family = NFPROTO_UNSPEC,
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.checkentry = nflog_tg_check,
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.destroy = nflog_tg_destroy,
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.target = nflog_tg,
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.targetsize = sizeof(struct xt_nflog_info),
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.me = THIS_MODULE,
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};
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static int __init nflog_tg_init(void)
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{
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return xt_register_target(&nflog_tg_reg);
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}
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static void __exit nflog_tg_exit(void)
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{
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xt_unregister_target(&nflog_tg_reg);
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}
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module_init(nflog_tg_init);
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module_exit(nflog_tg_exit);
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MODULE_SOFTDEP("pre: nfnetlink_log");
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