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

[Alexander Graf <graf@amazon.com>]

On 06.07.20 14:52, Jann Horn wrote:
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> 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
> 

Fair point. However, you could bump an epoch value on fork, no? I don't 
think we map anything in the vdso per-process today though ...


Alex



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