Date: Tue, 7 Sep 2010 13:13:45 +0200 From: Sebastian Krahmer <krahmer@...e.de> To: Andrew Morton <akpm@...ux-foundation.org> Cc: oss-security@...ts.openwall.com, security@...nel.org, spender@...ecurity.net Subject: Re: [Security] /proc infoleaks On Tue, Sep 07, 2010 at 03:51:03AM -0700, Andrew Morton wrote: > On Tue, 7 Sep 2010 10:35:46 +0200 Sebastian Krahmer <krahmer@...e.de> wrote: > > > I have been elected to receive the bashing from all sides, > > so here we go. > > It is not about a new vulnerability or even a new discussion > > but needs to be discussed, at least that we have a clear > > statement about the status quo. > > > > Recent i-CAN-haz-MODHARDEN.c has shown once *again* that > > certain file permissions make no sense except to exploitation > > development. There is no reason to have files like > > > > /proc/kallsyms > > /proc/slabinfo > > /proc/zoneinfo > > > > and probably a lot of others world readable. The symbol > > addresses might be hard-coded for a certain targetlist > > inside the exploit so you can argue that there > > wont be any protection benefit from making it unreadable. > > However this argument aint a reason to also leak it for self-compiled > > kernels and doesnt even hold for dynamic/runtime content > > like slabinfos etc. > > It would be nice to have something like > > > > echo 1 > /proc/quiet > > > > or something like a umask for kernel-owned proc > > entries so that you have a polite default and are > > still able to enable it for certain profiling tools > > or whereever you need it. > > chmod 0440 /proc/slabinfo > Heh, indeed. :-) Would it be a bad idea to have proc_create() use a more strict mode so it is non-leaking by default? Sebastian -- ~ ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@...e.de - SuSE Security Team ~ SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nuernberg)
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