include/linux/netlink.h:115:13: warning: ' conflicts with existing pse...' directive output truncated writing 57 bytes into a region of size 39

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   dd72f9c7e512da377074d47d990564959b772643
commit: 3c9561c0a5b988be3dfd24ea1de2301b95efc640 sfc: support TC decap rules matching on enc_ip_tos
date:   5 months ago
config: x86_64-randconfig-x013-20230730 (https://download.01.org/0day-ci/archive/20231019/202310191216.FAnRacs5-lkp@xxxxxxxxx/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231019/202310191216.FAnRacs5-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310191216.FAnRacs5-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

   In file included from include/uapi/linux/neighbour.h:6,
                    from include/linux/netdevice.h:46,
                    from include/net/sch_generic.h:5,
                    from include/net/pkt_cls.h:7,
                    from drivers/net/ethernet/sfc/tc.c:12:
   drivers/net/ethernet/sfc/tc.c: In function 'efx_tc_flower_record_encap_match':
>> include/linux/netlink.h:115:13: warning: ' conflicts with existing pse...' directive output truncated writing 57 bytes into a region of size 39 [-Wformat-truncation=]
     115 |         if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,               \
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     116 |                      "%s" fmt "%s", "", ##args, "") >=                         \
         |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/netlink.h:130:9: note: in expansion of macro 'NL_SET_ERR_MSG_FMT'
     130 |         NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)
         |         ^~~~~~~~~~~~~~~~~~
   drivers/net/ethernet/sfc/tc.c:507:33: note: in expansion of macro 'NL_SET_ERR_MSG_FMT_MOD'
     507 |                                 NL_SET_ERR_MSG_FMT_MOD(extack,
         |                                 ^~~~~~~~~~~~~~~~~~~~~~
   include/linux/netlink.h:115:13: note: directive argument in the range [0, 255]
     115 |         if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,               \
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     116 |                      "%s" fmt "%s", "", ##args, "") >=                         \
         |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/netlink.h:130:9: note: in expansion of macro 'NL_SET_ERR_MSG_FMT'
     130 |         NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)
         |         ^~~~~~~~~~~~~~~~~~
   drivers/net/ethernet/sfc/tc.c:507:33: note: in expansion of macro 'NL_SET_ERR_MSG_FMT_MOD'
     507 |                                 NL_SET_ERR_MSG_FMT_MOD(extack,
         |                                 ^~~~~~~~~~~~~~~~~~~~~~
   include/linux/netlink.h:115:13: note: 'snprintf' output 103 bytes into a destination of size 80
     115 |         if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,               \
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     116 |                      "%s" fmt "%s", "", ##args, "") >=                         \
         |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/netlink.h:130:9: note: in expansion of macro 'NL_SET_ERR_MSG_FMT'
     130 |         NL_SET_ERR_MSG_FMT((extack), KBUILD_MODNAME ": " fmt, ##args)
         |         ^~~~~~~~~~~~~~~~~~
   drivers/net/ethernet/sfc/tc.c:507:33: note: in expansion of macro 'NL_SET_ERR_MSG_FMT_MOD'
     507 |                                 NL_SET_ERR_MSG_FMT_MOD(extack,
         |                                 ^~~~~~~~~~~~~~~~~~~~~~


vim +115 include/linux/netlink.h

2d4bc93368f5a0 Johannes Berg 2017-04-12  106  
51c352bdbcd23d Edward Cree   2022-10-18  107  /* We splice fmt with %s at each end even in the snprintf so that both calls
51c352bdbcd23d Edward Cree   2022-10-18  108   * can use the same string constant, avoiding its duplication in .ro
51c352bdbcd23d Edward Cree   2022-10-18  109   */
51c352bdbcd23d Edward Cree   2022-10-18  110  #define NL_SET_ERR_MSG_FMT(extack, fmt, args...) do {			       \
51c352bdbcd23d Edward Cree   2022-10-18  111  	struct netlink_ext_ack *__extack = (extack);			       \
51c352bdbcd23d Edward Cree   2022-10-18  112  									       \
51c352bdbcd23d Edward Cree   2022-10-18  113  	if (!__extack)							       \
51c352bdbcd23d Edward Cree   2022-10-18  114  		break;							       \
51c352bdbcd23d Edward Cree   2022-10-18 @115  	if (snprintf(__extack->_msg_buf, NETLINK_MAX_FMTMSG_LEN,	       \
51c352bdbcd23d Edward Cree   2022-10-18  116  		     "%s" fmt "%s", "", ##args, "") >=			       \
51c352bdbcd23d Edward Cree   2022-10-18  117  	    NETLINK_MAX_FMTMSG_LEN)					       \
51c352bdbcd23d Edward Cree   2022-10-18  118  		net_warn_ratelimited("%s" fmt "%s", "truncated extack: ",      \
51c352bdbcd23d Edward Cree   2022-10-18  119  				     ##args, "\n");			       \
51c352bdbcd23d Edward Cree   2022-10-18  120  									       \
51c352bdbcd23d Edward Cree   2022-10-18  121  	do_trace_netlink_extack(__extack->_msg_buf);			       \
51c352bdbcd23d Edward Cree   2022-10-18  122  									       \
51c352bdbcd23d Edward Cree   2022-10-18  123  	__extack->_msg = __extack->_msg_buf;				       \
51c352bdbcd23d Edward Cree   2022-10-18  124  } while (0)
51c352bdbcd23d Edward Cree   2022-10-18  125  

:::::: The code at line 115 was first introduced by commit
:::::: 51c352bdbcd23d7ce46b06c1e64c82754dc44044 netlink: add support for formatted extack messages

:::::: TO: Edward Cree <ecree.xilinx@xxxxxxxxx>
:::::: CC: Jakub Kicinski <kuba@xxxxxxxxxx>

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