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    SubjectRe: [PATCH 1/2] LSM: Do not apply mmap_min_addr check to PROT_NONE
    > It's exactly the case that I did mention: an application's own attempt to
    > ensure robustness by doing a PROT_NONE mmap of the [0,0x10000) region. An
    > application cannot presume that this region is already precluded from being
    > used by any non-MAP_FIXED mmap across all systems and configurations, so
    > it's defensive coding to explicitly block it off with a PROT_NONE mapping.

    I don't see a realistic threat model in the example you give.

    Since mmap_min_addr is used to prevent a *malicious* process from
    maping the zero page and then taking advantage of a user-pointer
    dereference in the *kernel code*, I do not see what you gain by
    guaranteeing that the application *that you control* would never
    exploit such a vulnerability?

    Sorry if I'm being thick, but it would be helpful to me if you clarify.

    - Greg

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      Last update: 2011-10-28 15:39    [W:0.017 / U:18.172 seconds]
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