I have no experience of kernel programming or anything low level. I just watched this video and at 21:10 the presenter started to talk about modifying kernel memory using two pointers.
From my understanding he simply points pointer A to some user memory t1 and B to some kernel memory t2, and after a syscall (which looks like
memset) contents of t1 is copied to t2.
My question is: since this is mostly a concept demonstration, how does it work, and why the syscall does not check memory address? P.S. this is Cisco Unix 4.1.