Re: [Publicity] Technical / puzzle blog post on killing processes

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Thu, Apr 19, 2018 at 06:27:19PM +0100, George Dunlap wrote:
> The basic problem here is a race condition.  What `killall` does is:
> 
> 1. Read the list of processes
> 2. Call `kill(pid, sig)` on each one
> 
> In between 1 and each instance of 2, the kernel tasklist lock is
> released (since it has to return from the hypercall), giving the rogue

                                            ^ syscall ;-)

> process a chance to fork.  Indeed, it has many chances; since the
> second one takes a non-negligible amount of time, by the time you
> manage to find the rogue process, it's likely already forked, and
> perhaps even exited.

-- 
Anthony PERARD

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