CVE request: kernel: L2TP send buffer allocation size overflows

[Petr Matousek <pmatouse () redhat com>]

"Both PPPoL2TP (in net/l2tp/l2tp_ppp.c, pppol2tp_sendmsg()) and IPoL2TP (in
net/l2tp/l2tp_ip.c, l2tp_ip_sendmsg()) make calls to sock_wmalloc() that
perform arithmetic on the size argument without any maximum bound. As a result,
by issuing sendto() calls with very large sizes, this allocation size will wrap
and result in a small buffer being allocated, leading to ugliness immediately
after (probably kernel panics due to bad sk_buff tail position, but possibly
kernel heap corruption)."

Credit: Dan Rosenberg

Reference:
http://www.spinics.net/lists/netdev/msg145673.html
https://bugzilla.redhat.com/show_bug.cgi?id=651892

Thanks,
--
Petr Matousek / Red Hat Security Response Team