Dirty COW was a race-condition vulnerability in the Linux kernel. This vulnerability lived inside the kernel functions which handle the copy-on-write (COW) feature of memory mappings and when exploited allowed processes to write to read-only files.
An example use case of this vulnerability includes overwriting any SUID (Set User ID) binary such as passwd executable with a different elf executable (which we create) that executes /bin/sh to gain root privileges (as shown in this repository).
You can find more executables in Linux that have the SUID bit set and change them in the exploit code here: https://pentestlab.blog/2017/09/25/suid-executables/
Privilege Escalation PoC: Exploiting Dirty COW for Root Access (CVE-2016-5195) - Ran on Kali Linux 2016.2