Re: [PATCH net-next v2] af_unix: Refine UNIX pathname sockets autobind identifier length

[kernel test robot <lkp@intel.com>]

Hi Liang,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Liang-Jie/af_unix-Refine-UNIX-pathname-sockets-autobind-identifier-length/20250206-134846
base:   net-next/main
patch link:    https://lore.kernel.org/r/20250206054451.4070941-1-buaajxlj%40163.com
patch subject: [PATCH net-next v2] af_unix: Refine UNIX pathname sockets autobind identifier length
config: hexagon-randconfig-001-20250207 (https://download.01.org/0day-ci/archive/20250209/202502090056.Rl1rtpr5-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project 6807164500e9920638e2ab0cdb4bf8321d24f8eb)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250209/202502090056.Rl1rtpr5-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/202502090056.Rl1rtpr5-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/unix/af_unix.c:1222:2: warning: 'snprintf' will always be truncated; specified size is 5, but format string expands to at least 6 [-Wformat-truncation]
    1222 |         snprintf(addr->name->sun_path + 1, 5, "%05x", ordernum);
         |         ^
   1 warning generated.


vim +/snprintf +1222 net/unix/af_unix.c

  1190	
  1191	static int unix_autobind(struct sock *sk)
  1192	{
  1193		struct unix_sock *u = unix_sk(sk);
  1194		unsigned int new_hash, old_hash;
  1195		struct net *net = sock_net(sk);
  1196		struct unix_address *addr;
  1197		u32 lastnum, ordernum;
  1198		int err;
  1199	
  1200		err = mutex_lock_interruptible(&u->bindlock);
  1201		if (err)
  1202			return err;
  1203	
  1204		if (u->addr)
  1205			goto out;
  1206	
  1207		err = -ENOMEM;
  1208		addr = kzalloc(sizeof(*addr) + offsetof(struct sockaddr_un, sun_path) +
  1209				UNIX_AUTOBIND_LEN, GFP_KERNEL);
  1210		if (!addr)
  1211			goto out;
  1212	
  1213		addr->len = offsetof(struct sockaddr_un, sun_path) + UNIX_AUTOBIND_LEN;
  1214		addr->name->sun_family = AF_UNIX;
  1215		refcount_set(&addr->refcnt, 1);
  1216	
  1217		old_hash = sk->sk_hash;
  1218		ordernum = get_random_u32();
  1219		lastnum = ordernum & 0xFFFFF;
  1220	retry:
  1221		ordernum = (ordernum + 1) & 0xFFFFF;
> 1222		snprintf(addr->name->sun_path + 1, 5, "%05x", ordernum);
  1223	
  1224		new_hash = unix_abstract_hash(addr->name, addr->len, sk->sk_type);
  1225		unix_table_double_lock(net, old_hash, new_hash);
  1226	
  1227		if (__unix_find_socket_byname(net, addr->name, addr->len, new_hash)) {
  1228			unix_table_double_unlock(net, old_hash, new_hash);
  1229	
  1230			/* __unix_find_socket_byname() may take long time if many names
  1231			 * are already in use.
  1232			 */
  1233			cond_resched();
  1234	
  1235			if (ordernum == lastnum) {
  1236				/* Give up if all names seems to be in use. */
  1237				err = -ENOSPC;
  1238				unix_release_addr(addr);
  1239				goto out;
  1240			}
  1241	
  1242			goto retry;
  1243		}
  1244	
  1245		__unix_set_addr_hash(net, sk, addr, new_hash);
  1246		unix_table_double_unlock(net, old_hash, new_hash);
  1247		err = 0;
  1248	

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