Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo

[Pekka Enberg]

On Mon, Sep 19, 2011 at 8:35 PM, Vasiliy Kulikov <segoon@xxxxxxxxxxxx> wrote:
>> Yes, but there's no way for users to know where the allocations came from
>> if you mix them up with other kmalloc-128 call-sites. That way the number
>> of private files will stay private to the user, no? Doesn't that give you even
>> better protection against the infoleak?
>
> No, what it gives us is an obscurity, not a protection.  I'm sure it
> highly depends on the specific situation whether an attacker is able to
> identify whether the call is from e.g. ecryptfs or from VFS.  Also the
> correlation between the number in slabinfo and the real private actions
> still exists.

How is the attacker able to identify that we kmalloc()'d from ecryptfs or
VFS based on non-root /proc/slabinfo when the slab allocator itself does
not have that sort of information if you mix up the allocations? Isn't this
much stronger protection especially if you combine that with /proc/slabinfo
restriction?

                                  Pekka
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