Re: [RFC][PATCH] linux-2.6.2-rc2_vsyscall-gtod_B1.patch

From: Jamie Lokier (jamie_at_shareable.org)
Date: 02/03/04

  • Next message: Marc-Christian Petersen: "Re: broken maxcpus in 2.4.24" 
    Date:	Tue, 3 Feb 2004 08:52:24 +0000
To: Ulrich Drepper <drepper@redhat.com>

    Ulrich Drepper wrote:
    > You got to be kidding. Some object fixed in the address space which can
    > perform system calls. Nothing is more welcome to somebody trying to
    > exploit some bugs.

    Two approaches to randomising the vdso address:

      1. Selecting a random address at boot time. All tasks have the same
         vdso for that run of the kernel. Advantages: no MSR write at
         each context switch; could patch libsyscall.so at boot time with
         address if we were fanatical about optimisation (i.e. other
         libcs, not Glibc :) Disadvantages: the attacker may eventually
         learn the address.

      2. Select a random address for every new task. Advantages: harder
         to guess from studying a machine for a long time. Disadvantages:
         slower context switches; the gain from randomising each task is
         nothing if all the tasks are very long lived anyway.

    -- Jamie
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  • Next message: Marc-Christian Petersen: "Re: broken maxcpus in 2.4.24"

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