Re: [RFC PATCH] net: skb: on zero-copy formatted output to skb

Re: [RFC PATCH] net: skb: on zero-copy formatted output to skb

[kernel test robot]

Hi Dmitry,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]
[also build test WARNING on net/main linus/master v7.1-rc1 next-20260430]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Antipov/net-skb-on-zero-copy-formatted-output-to-skb/20260425-175341
base:   net-next/main
patch link:    https://lore.kernel.org/r/20260423073638.778334-1-dmantipov%40yandex.ru
patch subject: [RFC PATCH] net: skb: on zero-copy formatted output to skb
config: sparc64-allmodconfig (https://download.01.org/0day-ci/archive/20260503/202605030443.Enw1fif1-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260503/202605030443.Enw1fif1-lkp@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605030443.Enw1fif1-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/core/skbuff.c:7001:56: warning: diagnostic behavior may be improved by adding the 'format(printf, 2, 3)' attribute to the declaration of 'skb_printf' [-Wmissing-format-attribute]
    7001 |         len = vsnprintf(skb_tail_pointer(skb), size, fmt, args);
         |                                                               ^
   include/linux/skbuff.h:4295:5: note: 'skb_printf' declared here
    4295 | int skb_printf(struct sk_buff *skb, const char *fmt, ...);
         |     ^
   1 warning generated.


vim +7001 net/core/skbuff.c

  6994	
  6995	int skb_printf(struct sk_buff *skb, const char *fmt, ...)
  6996	{
  6997		int len, size = skb_availroom(skb);
  6998		va_list args;
  6999	
  7000		va_start(args, fmt);
> 7001		len = vsnprintf(skb_tail_pointer(skb), size, fmt, args);
  7002		va_end(args);
  7003	
  7004		if (unlikely(len >= size))
  7005			return -ENOSPC;
  7006	
  7007		skb->tail += len;
  7008		skb->len += len;
  7009		return len;
  7010	}
  7011	EXPORT_SYMBOL(skb_printf);
  7012	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki