Use IFNAMSIZ instead of a magic value for the length of an interface

name.

Prevent the kernel from potentially overflowing the interface name
variable.  The size argument of strlcpy is complex because the name is
not null-terminated in sdl_data.

2 files changed, 5 insertions, 4 deletions

diff --git a/sbin/ifconfig/ifconfig.c b/sbin/ifconfig/ifconfig.c
index 0e433a5..0e6ae2b 100644
--- a/sbin/ifconfig/ifconfig.c
+++ b/sbin/ifconfig/ifconfig.c
@@ -113,7 +113,7 @@ struct	in6_aliasreq	in6_addreq =
 struct	sockaddr_in	netmask;
 struct	netrange	at_nr;		/* AppleTalk net range */
 
-char	name[32];
+char	name[IFNAMSIZ];
 int	flags;
 int	setaddr;
 int	setipdst;
@@ -596,8 +596,9 @@ main(int argc, char *argv[])
 			addrcount++;
 			next += nextifm->ifm_msglen;
 		}
-		strncpy(name, sdl->sdl_data, sdl->sdl_nlen);
-		name[sdl->sdl_nlen] = '\0';
+		strlcpy(name, sdl->sdl_data,
+		    sizeof(name) <= sdl->sdl_nlen ?
+		    sizeof(name) : sdl->sdl_nlen + 1);
 
 		if (all || namesonly) {
 			if (uponly)
diff --git a/sbin/ifconfig/ifconfig.h b/sbin/ifconfig/ifconfig.h
index 7430c69..622be54 100644
--- a/sbin/ifconfig/ifconfig.h
+++ b/sbin/ifconfig/ifconfig.h
@@ -36,7 +36,7 @@
 
 extern struct ifreq ifr;
 
-extern char name[32];	/* name of interface */
+extern char name[IFNAMSIZ];	/* name of interface */
 extern int allmedia;
 extern int supmedia;
 struct afswtch;