CVE-2014-4943

A flaw was found in the way the pppol2tp_setsockopt() and pppol2tp_getsockopt() functions in the Linux kernel's PPP over L2TP implementation handled requests with a non-SOL_PPPOL2TP socket option level. A local, unprivileged user could use this flaw to escalate their privileges on the system.

For Red Hat Enterprise Linux 6 do --

]# echo "install pppol2tp /bin/true" > /etc/modprobe.d/pppol2tp.conf

For Red Hat Enterprise Linux 7 do --

]# echo "install l2tp_ppp /bin/true" > /etc/modprobe.d/l2t_pppp.conf

Or, alternatively, when pppol2tp/l2tp_ppp module can't be blacklisted and needs
to be loaded, you can use the following systemtap script --

1) On the host, save the following in a file with the ".stp" extension --

probe module("*l2tp*").function("pppol2tp_*etsockopt").call {
        $level = 273;
}

2) Install the "systemtap" package and any required dependencies. Refer to
the "2. Using SystemTap" chapter in the Red Hat Enterprise Linux 6
"SystemTap Beginners Guide" document, available from docs.redhat.com, for
information on installing the required -debuginfo packages.

3) Run the "stap -g [filename-from-step-1].stp" command as root.

If the host is rebooted, the changes will be lost and the script must be
run again.

Alternatively, build the systemtap script on a development system with
"stap -g -p 4 [filename-from-step-1].stp", distribute the resulting kernel
module to all affected systems, and run "staprun -L <module>" on those.
When using this approach only systemtap-runtime package is required on the
affected systems. Please notice that the kernel version must be the same across
all systems.