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    SubjectRe: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking
    On 11/10/2010 12:53 AM, Ingo Molnar wrote:
    > * H. Peter Anvin <> wrote:
    >> We already do virtual relocation on 32 bits, and replicating that on 64 bits
    >> wouldn't be hard. However, the linkage script strongly assumes congruency mod 2/4
    >> MiB, and that is probably nontrivial to change. However, that still gives about 9
    >> bits of entrophy to play with. The question is if that is enough, or if we'd have
    >> to do more clever hacks.
    > Even 1 bit of entropy would bring a visible improvement: a failed exploit attempt to
    > the wrong address can crash the kernel with a 50% chance. 9 bits would be very nice.
    > If an exploit can be brute-forced without crashing the kernel then only some
    > significantly large bitness would help. So while 9 bits would be rather low for a
    > user-space ASLR scheme [many user-space bugs can be brute-forced without crashing
    > the system and raising alarms], it's very attractive for kernel ASLR.

    Now, *relative* symbol addresses will typically not have any randomness
    at all, which may limit the usefulness, of course.


    H. Peter Anvin, Intel Open Source Technology Center
    I work for Intel. I don't speak on their behalf.

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      Last update: 2010-11-11 03:55    [W:0.028 / U:49.852 seconds]
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