Dirty Cow: Privilege Escalation Exploit, Linux Kernel

Okay so likely have heard about this, if you like me use Linux daily, in your college, professional or hobbyist life but like what the heck is it really?

To paraphrase from the initial disclosure docs:

the privilege-escalation vulnerability potentially allows any installed application, or malicious code smuggled onto a box, to gain root-level access and completely hijack the device.

The programming bug gets its name from the copy-on-write mechanism in the Linux kernel; the implementation is so broken, programs can set up a race condition to tamper with what should be a read-only root-owned executable mapped into memory

So exactly what does all that mean?  It means your web facing servers and even Androids have a big time issue with multi tasking in a sense.  This bug allows for what is called a ‘race condition’  which as you may have guessed makes for a first one in wins scenario.  The bad part is that that allows the kernel to be tricked into mapping a new ‘page’  (a coding term for the memory allocation) without fully un-allocating or ‘unlocking’  the previous one. This in turn allows for a bad memory page to get into a root-owned (the almighty full system admin) which is bad news.  The process that is overwritten or bypassed is called Copy-On-Write  (hence the COW part of the name) and being that the race condition is executed by using and triggering dirty paging within or  in an effort to gain privileged access its been Dubbed Dirty CoW.  If you feel so inclined to read the much more technical details feel free to read up on CVE 2016-5195