Re: useless kernel.maps_protect and more

From: Kees Cook
Date: Wed Jul 16 2008 - 10:58:20 EST


On Wed, Jul 16, 2008 at 06:11:35AM +0400, Alexey Dobriyan wrote:
> commit 5096add84b9e96e2e0a9c72675c442fe5433388a
> "proc: maps protection"
> commit 831830b5a2b5d413407adf380ef62fe17d6fcbf2
> "restrict reading from /proc/<pid>/maps to those who share ->mm or can ptrace pid"
> After Al added mm_for_maps(), maps_protect stopped controlling anything,
> because they're run at ->show time, but mm_for_maps() checks are done at
> ->start time.
> Unless anyone objects, I'll remove maps_protect.

As long as this provides the same protections as maps_protect, I'm fine
with it. I am a bit confused, though, since the reason I had to create
the sysctl entry in the first place was because akpm objected to the
maps file disappearing without a tunable. Has this objection gone away?

> Also, logic behind second commit applies to /proc/*/pagemap , don't you
> think?

If that file shows memory location, yes. What about the numa maps that
the first commit protects?



Kees Cook
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