Date: Wed, 6 Jul 2011 11:01:47 -0700 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Vasiliy Kulikov <segoon@...nwall.com> Cc: linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>, Andrew Morton <akpm@...ux-foundation.org>, "David S. Miller" <davem@...emloft.net>, Jiri Slaby <jslaby@...e.cz>, James Morris <jmorris@...ei.org>, Neil Brown <neilb@...e.de>, kernel-hardening@...ts.openwall.com Subject: Re: RLIMIT_NPROC check in set_user() On Wed, Jul 6, 2011 at 10:36 AM, Vasiliy Kulikov <segoon@...nwall.com> wrote: > On Sun, Jun 12, 2011 at 17:09 +0400, Vasiliy Kulikov wrote: >> I'd be happy to hear opinions about improving the fixes above or >> alternative fixes. > > No comments? Even "Sigh, what a nasty problem. But we cannot really > fix it without significantly breaking the stuff. Go and drink something." ? Thanks for reminding me. My reaction is: "let's just remote the crazy check from set_user() entirely". If somebody has credentials to change users, they damn well have credentials to override the RLIMIT_NPROC too, and as you say, failure is likely a bigger security threat than success. The whole point of RLIMIT_NPROC is to avoid fork-bombs. If we go over the limit for some other reason that is controlled by the super-user, who cares? So let's keep it in kernel/fork.c where we actually create a *new* process (and where everybody knows exactly what the limit means, and people who don't check for error cases are just broken). And remove it from everywhere else. Hmm? Linus
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