Messages in this thread |  | | | Date | Fri, 28 Oct 2011 15:36:33 +0200 | | Subject | Re: [PATCH 1/2] LSM: Do not apply mmap_min_addr check to PROT_NONE | | From | Gregory Sahanovitch <> |
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> 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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