Re: /proc/sys/kernel/pid_max issues

From: Herbert Poetzl (herbert_at_13thfloor.at)
Date: 09/13/04

  • Next message: Hugh Dickins: "Re: 2.6.9-rc1-mm4 sparc reiser4 build broken - undefined atomic_sub_and_test" 
    Date:	Mon, 13 Sep 2004 16:51:48 +0200
To: William Lee Irwin III <wli@holomorphy.com>

    On Mon, Sep 13, 2004 at 07:27:52AM -0700, William Lee Irwin III wrote:
    > On Mon, 2004-09-13 at 03:42, William Lee Irwin III wrote:
    > >> The resource tracking and locking implications of this are disturbing.
    > >> Would fully pseudorandom allocation be acceptable?
    >
    > On Mon, Sep 13, 2004 at 10:11:29AM -0400, Albert Cahalan wrote:
    > > There's no point.
    > > LRU reduces accidents that don't involve an attacker.
    > > Strong crypto random can make some attacks a bit harder.
    > > OpenBSD does this. It doesn't work well enough to bother
    > > with if the implementation is problematic; there's not
    > > much you can do while avoiding 64-bit or 128-bit PIDs.
    > > Pseudorandom is 100% useless.
    > > Per-user PID recycling would make it much harder for
    > > an attacker to grab a specific PID. Perhaps the attacker
    > > knows that a sched_setscheduler call is coming, and he
    > > has a way to make the right process restart or crash.
    > > Normally, this lets him get SCHED_FIFO or somesuch.
    > > With per-user PID recycling, it would be difficult for
    > > him to grab the desired PID.
    >
    > I'd suggest pushing for 64-bit+ pid's, then. IIRC most of the work
    > there is in userspace (the in-kernel part is trivial).

    except for the various 'assumptions' done in procfs
    to create the inode numbers ... but that is a different
    story ...

    best,
    Herbert

    > -- wli
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