When I applied the security update for dhclient to my SL6 netbook, my
DHCP client terminated with a segmentation fault whenever I tried to
get an IP.  Looking at the code, I discovered this was caused by a
null pointer dereference, so I have added code to make sure the point
isn't NULL before dereferencing it.

The patch is at the end of this message.  I also have RPMs fixing this
issue here:

http://samiam.org/SL6/dhclient-4.1.1-19.P1.el6.2.x86_64.rpm

http://samiam.org/SL6/dhcp-4.1.1-19.P1.el6.2.src.rpm

- Sam

--- dhcp-4.1.1-P1/common/lpf.c.orig     2011-08-17 01:34:53.750204048 -0400
+++ dhcp-4.1.1-P1/common/lpf.c  2011-08-17 01:34:56.754216522 -0400
@@ -634,6 +634,9 @@

        for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {

+               if (ifa->ifa_addr == NULL)
+                       continue;
+
                if (ifa->ifa_addr->sa_family != AF_PACKET)
                        continue;