linux-kernel - mm/hugetlb_cgroup.c:829:44: warning: '%s' directive output may be truncated writing up to 1623 bytes into a region of size between 32 and 63

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Message-ID: <202512212332.9lFRbgdS-lkp@intel.com>
Date: Sun, 21 Dec 2025 23:23:57 +0800
From: kernel test robot <lkp@...el.com>
To: Xiu Jianfeng <xiujianfeng@...wei.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: mm/hugetlb_cgroup.c:829:44: warning: '%s' directive output may be
 truncated writing up to 1623 bytes into a region of size between 32 and 63

Hi Xiu,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   9094662f6707d1d4b53d18baba459604e8bb0783
commit: 47179fe03588caa13a9bae642b058901709ddc55 mm/hugetlb_cgroup: prepare cftypes based on template
date:   1 year, 6 months ago
config: s390-randconfig-001-20251220 (https://download.01.org/0day-ci/archive/20251221/202512212332.9lFRbgdS-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251221/202512212332.9lFRbgdS-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202512212332.9lFRbgdS-lkp@intel.com/

All warnings (new ones prefixed by >>):

   mm/hugetlb_cgroup.c: In function 'hugetlb_cgroup_file_init':
>> mm/hugetlb_cgroup.c:829:44: warning: '%s' directive output may be truncated writing up to 1623 bytes into a region of size between 32 and 63 [-Wformat-truncation=]
     829 |   snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
         |                                            ^~
   mm/hugetlb_cgroup.c:829:3: note: 'snprintf' output between 2 and 1656 bytes into a destination of size 64
     829 |   snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
         |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   mm/hugetlb_cgroup.c:829:44: warning: '%s' directive output may be truncated writing up to 2087 bytes into a region of size between 32 and 63 [-Wformat-truncation=]
     829 |   snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
         |                                            ^~
   mm/hugetlb_cgroup.c:829:3: note: 'snprintf' output between 2 and 2120 bytes into a destination of size 64
     829 |   snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
         |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +829 mm/hugetlb_cgroup.c

   815	
   816	static void __init
   817	hugetlb_cgroup_cfttypes_init(struct hstate *h, struct cftype *cft,
   818				     struct cftype *tmpl, int tmpl_size)
   819	{
   820		char buf[32];
   821		int i, idx = hstate_index(h);
   822	
   823		/* format the size */
   824		mem_fmt(buf, sizeof(buf), huge_page_size(h));
   825	
   826		for (i = 0; i < tmpl_size; cft++, tmpl++, i++) {
   827			*cft = *tmpl;
   828			/* rebuild the name */
 > 829			snprintf(cft->name, MAX_CFTYPE_NAME, "%s.%s", buf, tmpl->name);
   830			/* rebuild the private */
   831			cft->private = MEMFILE_PRIVATE(idx, tmpl->private);
   832			/* rebuild the file_offset */
   833			if (tmpl->file_offset) {
   834				unsigned int offset = tmpl->file_offset;
   835	
   836				cft->file_offset = MEMFILE_OFFSET0(offset) +
   837						   MEMFILE_FIELD_SIZE(offset) * idx;
   838			}
   839	
   840			lockdep_register_key(&cft->lockdep_key);
   841		}
   842	}
   843	

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