Re: [RFC]: mm,power: introduce MADV_WIPEONSUSPEND

Jann Horn
2020-07-06T12:52:37Z

On Mon, Jul 6, 2020 at 2:27 PM Alexander Graf <graf@amazon.com> wrote:
> Unless we create a vsyscall that returns both the PID as well as the
> epoch and thus handles fork *and* suspend. I need to think about this a
> bit more :).

You can't reliably detect forking by checking the PID if it is
possible for multiple forks to be chained before the reuse check runs:

- pid 1000 remembers its PID
- pid 1000 forks, creating child pid 1001
- pid 1000 exits and is waited on by init
- the pid allocator wraps around
- pid 1001 forks, creating child pid 1000
- child with pid 1000 tries to check for forking, determines that its
PID is 1000, and concludes that it is still the original process