linux-kernel - Re: [PATCH v2] Document /proc/pid PID reuse behavior

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Message-ID: <4536090.43ZsV6LvYe@merkaba>
Date:   Wed, 07 Nov 2018 18:04:59 +0100
From:   Martin Steigerwald <martin@...htvoll.de>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Daniel Colascione <dancol@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, rppt@...ux.ibm.com,
        Tim Murray <timmurray@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Dennis Zhou (Facebook)" <dennisszhou@...il.com>,
        Prashant Dhamdhere <pdhamdhe@...hat.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2] Document /proc/pid PID reuse behavior

Michal Hocko - 07.11.18, 17:00:
> > > otherwise anybody could simply DoS the system
> > > by consuming all available pids.
> > 
> > People can do that today using the instrument of terror widely known
> > as fork(2). The only thing standing between fork(2) and a full
> > process table is RLIMIT_NPROC.
> 
> not really. If you really do care about pid space depletion then you
> should use pid cgroup controller.

Its not quite on-topic, but I am curious now: AFAIK PID limit is 16 
bits. Right? Could it be raised to 32 bits? I bet it would be a major 
change throughout different parts of the kernel.

16 bits sound a bit low these days, not only for PIDs, but also for 
connections / ports.

-- 
Martin