drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095

drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   f2e8a57ee9036c7d5443382b6c3c09b51a92ec7e
commit: 6a39e62abbafd1d58d1722f40c7d26ef379c6a2f lib: string.h: detect intra-object overflow in fortified string functions
date:   3 years ago
config: arm64-allmodconfig (https://download.01.org/0day-ci/archive/20231210/202312100355.lHoJPgKy-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231210/202312100355.lHoJPgKy-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/202312100355.lHoJPgKy-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/block/rnbd/rnbd-srv.c: In function 'process_msg_open.isra':
>> drivers/block/rnbd/rnbd-srv.c:616:51: warning: '%s' directive output may be truncated writing up to 254 bytes into a region of size between 0 and 4095 [-Wformat-truncation=]
     616 |                 snprintf(full_path, PATH_MAX, "%s/%s",
         |                                                   ^~
   In function 'rnbd_srv_get_full_path',
       inlined from 'process_msg_open.isra' at drivers/block/rnbd/rnbd-srv.c:721:14:
   drivers/block/rnbd/rnbd-srv.c:616:17: note: 'snprintf' output between 2 and 4351 bytes into a destination of size 4096
     616 |                 snprintf(full_path, PATH_MAX, "%s/%s",
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     617 |                          dev_search_path, dev_name);
         |                          ~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +616 drivers/block/rnbd/rnbd-srv.c

2de6c8de192b934 Jack Wang 2020-05-11  588  
2de6c8de192b934 Jack Wang 2020-05-11  589  static char *rnbd_srv_get_full_path(struct rnbd_srv_session *srv_sess,
2de6c8de192b934 Jack Wang 2020-05-11  590  				     const char *dev_name)
2de6c8de192b934 Jack Wang 2020-05-11  591  {
2de6c8de192b934 Jack Wang 2020-05-11  592  	char *full_path;
2de6c8de192b934 Jack Wang 2020-05-11  593  	char *a, *b;
2de6c8de192b934 Jack Wang 2020-05-11  594  
2de6c8de192b934 Jack Wang 2020-05-11  595  	full_path = kmalloc(PATH_MAX, GFP_KERNEL);
2de6c8de192b934 Jack Wang 2020-05-11  596  	if (!full_path)
2de6c8de192b934 Jack Wang 2020-05-11  597  		return ERR_PTR(-ENOMEM);
2de6c8de192b934 Jack Wang 2020-05-11  598  
2de6c8de192b934 Jack Wang 2020-05-11  599  	/*
2de6c8de192b934 Jack Wang 2020-05-11  600  	 * Replace %SESSNAME% with a real session name in order to
2de6c8de192b934 Jack Wang 2020-05-11  601  	 * create device namespace.
2de6c8de192b934 Jack Wang 2020-05-11  602  	 */
2de6c8de192b934 Jack Wang 2020-05-11  603  	a = strnstr(dev_search_path, "%SESSNAME%", sizeof(dev_search_path));
2de6c8de192b934 Jack Wang 2020-05-11  604  	if (a) {
2de6c8de192b934 Jack Wang 2020-05-11  605  		int len = a - dev_search_path;
2de6c8de192b934 Jack Wang 2020-05-11  606  
2de6c8de192b934 Jack Wang 2020-05-11  607  		len = snprintf(full_path, PATH_MAX, "%.*s/%s/%s", len,
2de6c8de192b934 Jack Wang 2020-05-11  608  			       dev_search_path, srv_sess->sessname, dev_name);
2de6c8de192b934 Jack Wang 2020-05-11  609  		if (len >= PATH_MAX) {
2de6c8de192b934 Jack Wang 2020-05-11  610  			pr_err("Too long path: %s, %s, %s\n",
2de6c8de192b934 Jack Wang 2020-05-11  611  			       dev_search_path, srv_sess->sessname, dev_name);
2de6c8de192b934 Jack Wang 2020-05-11  612  			kfree(full_path);
2de6c8de192b934 Jack Wang 2020-05-11  613  			return ERR_PTR(-EINVAL);
2de6c8de192b934 Jack Wang 2020-05-11  614  		}
2de6c8de192b934 Jack Wang 2020-05-11  615  	} else {
2de6c8de192b934 Jack Wang 2020-05-11 @616  		snprintf(full_path, PATH_MAX, "%s/%s",
2de6c8de192b934 Jack Wang 2020-05-11  617  			 dev_search_path, dev_name);
2de6c8de192b934 Jack Wang 2020-05-11  618  	}
2de6c8de192b934 Jack Wang 2020-05-11  619  
2de6c8de192b934 Jack Wang 2020-05-11  620  	/* eliminitate duplicated slashes */
2de6c8de192b934 Jack Wang 2020-05-11  621  	a = strchr(full_path, '/');
2de6c8de192b934 Jack Wang 2020-05-11  622  	b = a;
2de6c8de192b934 Jack Wang 2020-05-11  623  	while (*b != '\0') {
2de6c8de192b934 Jack Wang 2020-05-11  624  		if (*b == '/' && *a == '/') {
2de6c8de192b934 Jack Wang 2020-05-11  625  			b++;
2de6c8de192b934 Jack Wang 2020-05-11  626  		} else {
2de6c8de192b934 Jack Wang 2020-05-11  627  			a++;
2de6c8de192b934 Jack Wang 2020-05-11  628  			*a = *b;
2de6c8de192b934 Jack Wang 2020-05-11  629  			b++;
2de6c8de192b934 Jack Wang 2020-05-11  630  		}
2de6c8de192b934 Jack Wang 2020-05-11  631  	}
2de6c8de192b934 Jack Wang 2020-05-11  632  	a++;
2de6c8de192b934 Jack Wang 2020-05-11  633  	*a = '\0';
2de6c8de192b934 Jack Wang 2020-05-11  634  
2de6c8de192b934 Jack Wang 2020-05-11  635  	return full_path;
2de6c8de192b934 Jack Wang 2020-05-11  636  }
2de6c8de192b934 Jack Wang 2020-05-11  637  

:::::: The code at line 616 was first introduced by commit
:::::: 2de6c8de192b9341ffa5e84afe1ce6196d4eef41 block/rnbd: server: main functionality

:::::: TO: Jack Wang <jinpu.wang@cloud.ionos.com>
:::::: CC: Jason Gunthorpe <jgg@mellanox.com>

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