CVE request - kernel: infoleak if print-fatal-signals=1

[Eugene Teo <eugene () redhat com>]

Description from the upstream patch:
When print-fatal-signals is enabled it's possible to dump any memory 
reachable by the kernel to the log by simply jumping to that address 
from user space.

Or crash the system if there's some hardware with read side effects.

The fatal signals handler will dump 16 bytes at the execution address, 
which is fully controlled by ring 3.

In addition when something jumps to an unmapped address there will be up 
to 16 additional useless page faults, which might be potentially slow 
(and at least is not very efficient)

Fortunately this option is off by default and only there on i386.

But fix it by hecking for kernel addresses and also stopping when 
there's a page fault.

References:
http://patchwork.kernel.org/patch/69752/
http://git.kernel.org/linus/b45c6e76bc2c72f6426c14bed64fdcbc9bf37cb0
https://bugzilla.redhat.com/show_bug.cgi?id=554578

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