Re: net/mptcp/pm_netlink.c:1169 mptcp_pm_parse_pm_addr_attr() warn: missing error code? 'err'

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Fri, 2 Dec 2022, Dan Carpenter wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   a4412fdd49dc011bcc2c0d81ac4cab7457092650
> commit: 982f17ba1a2534b878fbcb1a5273bfbc551c5397 mptcp: netlink: split mptcp_pm_parse_addr into two functions
> config: i386-randconfig-m021
> compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
>
> smatch warnings:
> net/mptcp/pm_netlink.c:1169 mptcp_pm_parse_pm_addr_attr() warn: missing error code? 'err'
>
> vim +/err +1169 net/mptcp/pm_netlink.c
>
> 982f17ba1a2534 Florian Westphal 2022-05-03  1145  static int mptcp_pm_parse_pm_addr_attr(struct nlattr *tb[],
> 982f17ba1a2534 Florian Westphal 2022-05-03  1146  				       const struct nlattr *attr,
> 982f17ba1a2534 Florian Westphal 2022-05-03  1147  				       struct genl_info *info,
> 982f17ba1a2534 Florian Westphal 2022-05-03  1148  				       struct mptcp_addr_info *addr,
> 982f17ba1a2534 Florian Westphal 2022-05-03  1149  				       bool require_family)
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1150  {
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1151  	int err, addr_addr;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1152
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1153  	if (!attr) {
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1154  		GENL_SET_ERR_MSG(info, "missing address info");
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1155  		return -EINVAL;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1156  	}
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1157
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1158  	/* no validation needed - was already done via nested policy */
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1159  	err = nla_parse_nested_deprecated(tb, MPTCP_PM_ADDR_ATTR_MAX, attr,
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1160  					  mptcp_pm_addr_policy, info->extack);
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1161  	if (err)
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1162  		return err;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1163
> 982f17ba1a2534 Florian Westphal 2022-05-03  1164  	if (tb[MPTCP_PM_ADDR_ATTR_ID])
> 982f17ba1a2534 Florian Westphal 2022-05-03  1165  		addr->id = nla_get_u8(tb[MPTCP_PM_ADDR_ATTR_ID]);
> 982f17ba1a2534 Florian Westphal 2022-05-03  1166
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1167  	if (!tb[MPTCP_PM_ADDR_ATTR_FAMILY]) {
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1168  		if (!require_family)
> 982f17ba1a2534 Florian Westphal 2022-05-03 @1169  			return err;
>
> "err" is zero at this point.  Presumably a negative error code was
> intended.

Hi Dan -

The intended error code is 0 here: the return happens if no 
MPTCP_PM_ADDR_ATTR_FAMILY value is present and require_family is false.

It would be clearer to "return 0;", but the code is working as expected.


Could you be sure to cc mptcp@lists.linux.dev and 
matthieu.baerts@tessares.net for future MPTCP issues?

Thanks,

Mat


>
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1170
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1171  		NL_SET_ERR_MSG_ATTR(info->extack, attr,
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1172  				    "missing family");
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1173  		return -EINVAL;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1174  	}
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1175
> 982f17ba1a2534 Florian Westphal 2022-05-03  1176  	addr->family = nla_get_u16(tb[MPTCP_PM_ADDR_ATTR_FAMILY]);
> 982f17ba1a2534 Florian Westphal 2022-05-03  1177  	if (addr->family != AF_INET
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1178  #if IS_ENABLED(CONFIG_MPTCP_IPV6)
> 982f17ba1a2534 Florian Westphal 2022-05-03  1179  	    && addr->family != AF_INET6
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1180  #endif
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1181  	    ) {
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1182  		NL_SET_ERR_MSG_ATTR(info->extack, attr,
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1183  				    "unknown address family");
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1184  		return -EINVAL;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1185  	}
> 982f17ba1a2534 Florian Westphal 2022-05-03  1186  	addr_addr = mptcp_pm_family_to_addr(addr->family);
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1187  	if (!tb[addr_addr]) {
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1188  		NL_SET_ERR_MSG_ATTR(info->extack, attr,
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1189  				    "missing address data");
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1190  		return -EINVAL;
> 01cacb00b35cb6 Paolo Abeni      2020-03-27  1191  	}
>
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
>
>

--
Mat Martineau
Intel