It’d be redundant for me to write up the whole explanation here, but the short version is that every process has its own memory space, provided in a clean state by the OS, that other processes can’t read from or write to, regardless of pointer values. The same pointer value in two processes doesn’t refer to the same memory unless there’s specific coordination. Keywords you can use to read more about the long version on previous Wikipedia link.
> Or is that always formatted by the next process' vm?
So yes, that’s sort of how it is.
You can read and write to other processes memory addresses on Linux using /proc/mem,
https://renenyffenegger.ch/notes/Linux/memory/read-write-ano...
You need the same access as you would for connecting gdb, so generally need to be running in the same uid, or be root.