Re: jit code and securelevel

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Christos Zoulas wrote:
> In article <20150101153259.GA2442@neva>,
> Alexander Nasonov  <alnsn%yandex.ru@localhost> wrote:
> >I don't remember seeing a policy on disabling jit code at securelevel
> >1 or higher. Is it something we should add?
> 
> I am not sure that we should add it because the code it generates is tightly
> conrolled by the kernel.

On a (misconfigured) system with enhanced permissions for tcpdump or
for some other pcap program, one can craft a special JIT code to help them
exploit a bug in the kernel:
http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.html

Function pointer of jit code is readable via kmem.

Alex