netdev - Re: [PATCH net v5 1/2] net: netfilter: Limit the number of ftp helper port attempts

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Date:   Mon, 20 Sep 2021 14:05:28 +0800
From:   kernel test robot <lkp@...el.com>
To:     Cole Dishington <Cole.Dishington@...iedtelesis.co.nz>,
        pablo@...filter.org, kadlec@...filter.org, fw@...len.de,
        davem@...emloft.net, kuba@...nel.org, shuah@...nel.org
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org
Subject: Re: [PATCH net v5 1/2] net: netfilter: Limit the number of ftp
 helper port attempts

Hi Cole,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on net/master]

url:    https://github.com/0day-ci/linux/commits/Cole-Dishington/Fix-port-selection-of-FTP-for-NF_NAT_RANGE_PROTO_SPECIFIED/20210920-090056
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git e30cd812dffadc58241ae378e48728e6a161becd
config: x86_64-randconfig-a002-20210920 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project c8b3d7d6d6de37af68b2f379d0e37304f78e115f)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/b90b875dc5be3c59ec418ce403a8d749690a24ec
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Cole-Dishington/Fix-port-selection-of-FTP-for-NF_NAT_RANGE_PROTO_SPECIFIED/20210920-090056
        git checkout b90b875dc5be3c59ec418ce403a8d749690a24ec
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> net/netfilter/nf_nat_ftp.c:117:37: warning: more '%' conversions than data arguments [-Wformat-insufficient-args]
                   nf_ct_helper_log(skb, ct, "tried %u ports, all were in use");
                                                    ~^
   1 warning generated.


vim +117 net/netfilter/nf_nat_ftp.c

    60	
    61	/* So, this packet has hit the connection tracking matching code.
    62	   Mangle it, and change the expectation to match the new version. */
    63	static unsigned int nf_nat_ftp(struct sk_buff *skb,
    64				       enum ip_conntrack_info ctinfo,
    65				       enum nf_ct_ftp_type type,
    66				       unsigned int protoff,
    67				       unsigned int matchoff,
    68				       unsigned int matchlen,
    69				       struct nf_conntrack_expect *exp)
    70	{
    71		union nf_inet_addr newaddr;
    72		u_int16_t port;
    73		int dir = CTINFO2DIR(ctinfo);
    74		struct nf_conn *ct = exp->master;
    75		unsigned int i, min, max, range_size;
    76		static const unsigned int max_attempts = 128;
    77		char buffer[sizeof("|1||65535|") + INET6_ADDRSTRLEN];
    78		unsigned int buflen;
    79		int ret;
    80	
    81		pr_debug("type %i, off %u len %u\n", type, matchoff, matchlen);
    82	
    83		/* Connection will come from wherever this packet goes, hence !dir */
    84		newaddr = ct->tuplehash[!dir].tuple.dst.u3;
    85		exp->saved_proto.tcp.port = exp->tuple.dst.u.tcp.port;
    86		exp->dir = !dir;
    87	
    88		/* When you see the packet, we need to NAT it the same as the
    89		 * this one. */
    90		exp->expectfn = nf_nat_follow_master;
    91	
    92		min = ntohs(exp->saved_proto.tcp.port);
    93		max = 65535;
    94	
    95		/* Try to get same port */
    96		ret = nf_ct_expect_related(exp, 0);
    97	
    98		/* if same port is not in range or available, try to change it. */
    99		if (ret != 0) {
   100			range_size = max - min + 1;
   101			if (range_size > max_attempts)
   102				range_size = max_attempts;
   103	
   104			port = min + prandom_u32_max(max - min);
   105			for (i = 0; i < range_size; i++) {
   106				exp->tuple.dst.u.tcp.port = htons(port);
   107				ret = nf_ct_expect_related(exp, 0);
   108				if (ret != -EBUSY)
   109					break;
   110				port++;
   111				if (port > max)
   112					port = min;
   113			}
   114		}
   115	
   116		if (ret != 0) {
 > 117			nf_ct_helper_log(skb, ct, "tried %u ports, all were in use");
   118			return NF_DROP;
   119		}
   120	
   121		buflen = nf_nat_ftp_fmt_cmd(ct, type, buffer, sizeof(buffer),
   122					    &newaddr, port);
   123		if (!buflen)
   124			goto out;
   125	
   126		pr_debug("calling nf_nat_mangle_tcp_packet\n");
   127	
   128		if (!nf_nat_mangle_tcp_packet(skb, ct, ctinfo, protoff, matchoff,
   129					      matchlen, buffer, buflen))
   130			goto out;
   131	
   132		return NF_ACCEPT;
   133	
   134	out:
   135		nf_ct_helper_log(skb, ct, "cannot mangle packet");
   136		nf_ct_unexpect_related(exp);
   137		return NF_DROP;
   138	}
   139	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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