Explicitly truncate snprintf arguments for GCC 8+

udev-device.c: In function 'udev_device_new_from_devnum':
udev-device.c:100:23: error: '.PCI_ID' directive output may be truncated writing 7 bytes into a region of size between 1 and 32 [-Werror=format-truncation=]
  100 |  snprintf(buf, 32, "%s.PCI_ID", devbuf);
      |                       ^~~~~~~
udev-device.c:100:2: note: 'snprintf' output between 8 and 39 bytes into a destination of size 32
  100 |  snprintf(buf, 32, "%s.PCI_ID", devbuf);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
udev-device.c:93:2: error: 'strncpy' specified bound 32 equals destination size [-Werror=stringop-truncation]
   93 |  strncpy(devbuf, devpath + 1, 32);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
udev-utils.c: In function 'set_parent':
udev-utils.c:501:34: error: '%s' directive output may be truncated writing up to 79 bytes into a region of size 28 [-Werror=format-truncation=]
  501 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%desc", devname, unit);
      |                                  ^~             ~~~~~~~
udev-utils.c:501:2: note: 'snprintf' output 12 or more bytes (assuming 91) into a destination of size 32
  501 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%desc", devname, unit);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
udev-utils.c:507:34: error: '%s' directive output may be truncated writing up to 79 bytes into a region of size 28 [-Werror=format-truncation=]
  507 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%pnpinfo", devname, unit);
      |                                  ^~                ~~~~~~~
udev-utils.c:507:2: note: 'snprintf' output 15 or more bytes (assuming 94) into a destination of size 32
  507 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%pnpinfo", devname, unit);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
udev-utils.c:512:34: error: '%s' directive output may be truncated writing up to 79 bytes into a region of size 28 [-Werror=format-truncation=]
  512 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%parent", devname, unit);
      |                                  ^~               ~~~~~~~
udev-utils.c:512:2: note: 'snprintf' output 14 or more bytes (assuming 93) into a destination of size 32
  512 |  snprintf(mib, sizeof(mib), "dev.%s.%s.%%parent", devname, unit);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Author: jbeich

udev-device.c

@@ -90,14 +90,14 @@ udev_device_new_from_devnum(struct udev *udev, char type, dev_t devnum)
 
 	TRC("(%d) -> %s", (int)devnum, devpath);
 	syspath = get_syspath_by_devpath(devpath);
-	strncpy(devbuf, devpath + 1, 32);
+	strncpy(devbuf, devpath + 1, 31);
 	devbufptr = devbuf;
 	devbufptr = strchrnul(devbufptr, '/');
 	while (*devbufptr != '\0') {
 		*devbufptr = '.';
 		devbufptr = strchrnul(devbufptr, '/');
 	}
-	snprintf(buf, 32, "%s.PCI_ID", devbuf);
+	snprintf(buf, 32, "%.24s.PCI_ID", devbuf);
 	buflen = 32;
 
 	sysctlbyname(buf, devbuf, &buflen, NULL, 0);

udev-utils.c

@@ -512,18 +512,18 @@ set_parent(struct udev_device *ud)
 	snprintf(devname, len + 1, "%s", sysname);
 	unit = sysname + len;
 
-	snprintf(mib, sizeof(mib), "dev.%s.%s.%%desc", devname, unit);
+	snprintf(mib, sizeof(mib), "dev.%.17s.%.3s.%%desc", devname, unit);
 	len = sizeof(name);
 	if (sysctlbyname(mib, name, &len, NULL, 0) < 0)
 		return;
 	*(strchrnul(name, ',')) = '\0';	/* strip name */
 
-	snprintf(mib, sizeof(mib), "dev.%s.%s.%%pnpinfo", devname, unit);
+	snprintf(mib, sizeof(mib), "dev.%.14s.%.3s.%%pnpinfo", devname, unit);
 	len = sizeof(pnpinfo);
 	if (sysctlbyname(mib, pnpinfo, &len, NULL, 0) < 0)
 		return;
 
-	snprintf(mib, sizeof(mib), "dev.%s.%s.%%parent", devname, unit);
+	snprintf(mib, sizeof(mib), "dev.%.15s.%.3s.%%parent", devname, unit);
 	len = sizeof(parentname);
 	if (sysctlbyname(mib, parentname, &len, NULL, 0) < 0)
 		return;