[alobakin:ip_tunnel 31/36] net/ipv4/ipip.c:247:54: sparse: sparse: Using plain integer as NULL pointer

[kernel test robot]

tree:   https://github.com/alobakin/linux ip_tunnel
head:   f6d5ecb4aceaf8c0da5503832a20129ac8c935df
commit: d979e3037463d961efe6c673bed1e4cc496ab2ce [31/36] net, tunnels: convert __be16 tunnel flags to bitmaps
config: x86_64-randconfig-s021 (https://download.01.org/0day-ci/archive/20220814/202208141837.tcObXYYV-lkp@xxxxxxxxx/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-39-gce1a6720-dirty
        # https://github.com/alobakin/linux/commit/d979e3037463d961efe6c673bed1e4cc496ab2ce
        git remote add alobakin https://github.com/alobakin/linux
        git fetch --no-tags alobakin ip_tunnel
        git checkout d979e3037463d961efe6c673bed1e4cc496ab2ce
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=x86_64 SHELL=/bin/bash net/ipv4/ net/ipv6/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

sparse warnings: (new ones prefixed by >>)
>> net/ipv4/ipip.c:247:54: sparse: sparse: Using plain integer as NULL pointer
--
>> net/ipv6/ip6_tunnel.c:935:56: sparse: sparse: Using plain integer as NULL pointer

vim +247 net/ipv4/ipip.c

1b69e7e6c4da1e8 Simon Horman       2016-07-07  214  
1b69e7e6c4da1e8 Simon Horman       2016-07-07  215  static int ipip_tunnel_rcv(struct sk_buff *skb, u8 ipproto)
^1da177e4c3f415 Linus Torvalds     2005-04-16  216  {
fd58156e456d9f6 Pravin B Shelar    2013-03-25  217  	struct net *net = dev_net(skb->dev);
fd58156e456d9f6 Pravin B Shelar    2013-03-25  218  	struct ip_tunnel_net *itn = net_generic(net, ipip_net_id);
d979e3037463d96 Alexander Lobakin  2022-05-04  219  	IP_TUNNEL_DECLARE_FLAGS(flags) = { };
cfc7381b3002756 Alexei Starovoitov 2016-09-15  220  	struct metadata_dst *tun_dst = NULL;
^1da177e4c3f415 Linus Torvalds     2005-04-16  221  	struct ip_tunnel *tunnel;
3d7b46cd20e300b Pravin B Shelar    2013-06-17  222  	const struct iphdr *iph;
3c97af99a5aa17f Eric Dumazet       2010-09-27  223  
d979e3037463d96 Alexander Lobakin  2022-05-04  224  	__set_bit(IP_TUNNEL_NO_KEY_BIT, flags);
d979e3037463d96 Alexander Lobakin  2022-05-04  225  
3d7b46cd20e300b Pravin B Shelar    2013-06-17  226  	iph = ip_hdr(skb);
d979e3037463d96 Alexander Lobakin  2022-05-04  227  	tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, flags, iph->saddr,
d979e3037463d96 Alexander Lobakin  2022-05-04  228  				  iph->daddr, 0);
fd58156e456d9f6 Pravin B Shelar    2013-03-25  229  	if (tunnel) {
1b69e7e6c4da1e8 Simon Horman       2016-07-07  230  		const struct tnl_ptk_info *tpi;
1b69e7e6c4da1e8 Simon Horman       2016-07-07  231  
1b69e7e6c4da1e8 Simon Horman       2016-07-07  232  		if (tunnel->parms.iph.protocol != ipproto &&
1b69e7e6c4da1e8 Simon Horman       2016-07-07  233  		    tunnel->parms.iph.protocol != 0)
1b69e7e6c4da1e8 Simon Horman       2016-07-07  234  			goto drop;
1b69e7e6c4da1e8 Simon Horman       2016-07-07  235  
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  236  		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  237  			goto drop;
1b69e7e6c4da1e8 Simon Horman       2016-07-07  238  #if IS_ENABLED(CONFIG_MPLS)
1b69e7e6c4da1e8 Simon Horman       2016-07-07  239  		if (ipproto == IPPROTO_MPLS)
1b69e7e6c4da1e8 Simon Horman       2016-07-07  240  			tpi = &mplsip_tpi;
1b69e7e6c4da1e8 Simon Horman       2016-07-07  241  		else
1b69e7e6c4da1e8 Simon Horman       2016-07-07  242  #endif
1b69e7e6c4da1e8 Simon Horman       2016-07-07  243  			tpi = &ipip_tpi;
1b69e7e6c4da1e8 Simon Horman       2016-07-07  244  		if (iptunnel_pull_header(skb, 0, tpi->proto, false))
737e828bdbdaf2f Li Hongjun         2013-08-28  245  			goto drop;
cfc7381b3002756 Alexei Starovoitov 2016-09-15  246  		if (tunnel->collect_md) {
cfc7381b3002756 Alexei Starovoitov 2016-09-15 @247  			tun_dst = ip_tun_rx_dst(skb, 0, 0, 0);
cfc7381b3002756 Alexei Starovoitov 2016-09-15  248  			if (!tun_dst)
cfc7381b3002756 Alexei Starovoitov 2016-09-15  249  				return 0;
cfc7381b3002756 Alexei Starovoitov 2016-09-15  250  		}
7ad136fd288c0e0 Guillaume Nault    2021-06-25  251  		skb_reset_mac_header(skb);
7ad136fd288c0e0 Guillaume Nault    2021-06-25  252  
cfc7381b3002756 Alexei Starovoitov 2016-09-15  253  		return ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error);
^1da177e4c3f415 Linus Torvalds     2005-04-16  254  	}
^1da177e4c3f415 Linus Torvalds     2005-04-16  255  
^1da177e4c3f415 Linus Torvalds     2005-04-16  256  	return -1;
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  257  
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  258  drop:
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  259  	kfree_skb(skb);
eccc1bb8d4b4cf6 stephen hemminger  2012-09-25  260  	return 0;
^1da177e4c3f415 Linus Torvalds     2005-04-16  261  }
^1da177e4c3f415 Linus Torvalds     2005-04-16  262  

:::::: The code at line 247 was first introduced by commit
:::::: cfc7381b3002756b1dcada32979e942aa3126e31 ip_tunnel: add collect_md mode to IPIP tunnel

:::::: TO: Alexei Starovoitov <ast@xxxxxx>
:::::: CC: David S. Miller <davem@xxxxxxxxxxxxx>

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