CVE-2009-0778 kernel: rt_cache leak

[Eugene Teo <eugene () redhat com>]

Reported by Hector Herrera:
A "REJECT" route in a software router (ip_forward = 1) based on CentOS 
5.2 will cause the kernel to lose track of cached routes.  Once the 
number of allocated route cache objects (as indicated by the value of 
ip_dst_cache in /proc/slabinfo) reaches the value of 
/proc/sys/net/ipv4/route/max_size - 1, the kernel will complain with a 
'dst cache overflow' errors for every received packet and all network 
connectivity will cease.

But was introduced in upstream commit 8b7817f3a95. It was later fixed in 
upstream commit 7c0ecc4c4f.

Workaround:
- either remove or replace the "REJECT" route with a different 
alternative such as 'ip route add 10.10.0.0/16 via 127.0.0.1'.
- using iptables.

References:
https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2009-0778

Thanks, Eugene
--
Eugene Teo / Red Hat Security Response Team