[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Wed, 15 Sep 2010 00:27:58 +0200
From: pageexec@...email.hu
To: Roland McGrath <roland@...hat.com>
CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Brad Spengler <spender@...ecurity.net>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, oss-security@...ts.openwall.com,
Solar Designer <solar@...nwall.com>,
Kees Cook <kees.cook@...onical.com>, Al Viro <viro@...iv.linux.org.uk>,
Oleg Nesterov <oleg@...hat.com>, Neil Horman <nhorman@...driver.com>,
linux-fsdevel@...r.kernel.org, Eugene Teo <eugene@...hat.com>
Subject: Re: [PATCH 1/3] setup_arg_pages: diagnose excessive argument size
On 14 Sep 2010 at 14:16, Roland McGrath wrote:
> > obviously an AT_ARGMAX computed at execve time would be based on the rlimits
> > as well and if later userland changed the rlimits, it'd be userland's problem,
> > not that of the kernel (or the kernel could refuse a change that would violate
> > its earlier promise).
>
> This would thoroughly defeat the purpose of adding the thing. The
> only reason to have a new thing is so that userland does not have to
> mirror the kernel's policy (as it attempts to do now, with the 1/4
> calculation). If the new thing is not something that userland can
> use consistently so as not to have to know what the kernel's actual
> policy is, then I don't see the point of it at all.
userland could never rely on the kernel's policy at all since get_arg_page
could have failed for more reasons than overstepping the currently hardcoded
ARG_MAX check in there. so what AT_ARGMAX would buy us is to allow the kernel
policy to change over time, but it's never been about guarantees, whether
POSIX wants such a thing or not.
> > > auxv is only appropriate for things that
> > > are known at the time of the exec and won't change thereafter.
> >
> > you mean stuff like AT_EUID et al.? ;)
>
> The information that these give is about the conditions at startup.
> That's what they mean to userland, and userland only uses them to know
> the situation before it has made any calls. The definition of AT_EUID
> is "effective user ID at program startup", and that fact does not
> change.
just for my own curiosity, where does this definition come from?
Powered by blists - more mailing lists
Please check out the
Open Source Software Security Wiki, which is counterpart to this
mailing list.
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
