Re: [RFC][PATCH] procfs: add privacy options

[Rene Scharfe <rene.scharfe@lsrfire.ath.cx>]

Eric W. Biederman schrieb:
> I don't really like filesystem magic options as kernel boot time options.
> Mount time or runtime options are probably more interesting.
> 
> How is it expected that users will use this?

I don't expect admins to switch "privacy" on and off very often.  Once
would be enough, I hope.

Mount options would be easier to use, I agree, but I doubt the added
complexity is worth it.  Kernel options for procfs are not _that_
magical because the kernel mounts it internally, so it's a kernel part,
not a real filesystem ;-)

One question I couldn't find a good answer for regarding remount
options: what to do with processes that have cd'd into a /proc/<pid> dir
belonging to another user when the privacy option is being turned on?
Letting them keep their access is counter-intuitive and taking it away
would need quite invasive changes compared to my patch, I think.

> A lot of the privacy you are talking about is provided by the may_ptrace
> checks in the more sensitive parts of proc so we may want to extend
> that.

You mean using ptrace_may_attach() and/or MAY_PTRACE() for determining
access to all (or at least more) files in /proc/<pid> instead of my
proposed "chmod 500"?  What are the advantages?

Thanks,
René