CVE-2009-4272 kernel: emergency route cache flushing leads to node deadlock

[Eugene Teo <eugeneteo () kernel sg>]

Reported by the Parallels Virtuozzo Containers team.

If an attacker was able to cause a large enough number of collisions in 
the routing hash table (via specially-crafted packets) for the emergency 
route flush to trigger, a deadlock could occur, or if the kernel routing 
cache was disabled, an uninitialized pointer would be left behind after 
a route lookup, leading to a NULL pointer dereference. Both caused by 
the same issue.

Introduced via:
c6153b5b77650879d78dec76414213c76dd8d574 v2.6.27-rc4~39^2~41
1080d709fb9d8cd4392f93476ee46a9d6ea05a5b v2.6.29-rc1~581^2~973

Patches:
https://bugzilla.redhat.com/show_bug.cgi?id=545411#c6
https://bugzilla.redhat.com/show_bug.cgi?id=545411#c15

Reference:
https://bugzilla.redhat.com/show_bug.cgi?id=545411

Thanks, Eugene