From: Vasiliy Kulikov <segoon@openwall.com>
To: kernel-hardening@lists.openwall.com
Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman <gregkh@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
"David S. Miller" <davem@davemloft.net>,
Jiri Slaby <jslaby@suse.cz>, James Morris <jmorris@namei.org>,
Neil Brown <neilb@suse.de>
Subject: Re: [kernel-hardening] Re: RLIMIT_NPROC check in set_user()
Date: Wed, 6 Jul 2011 22:59:32 +0400 [thread overview]
Message-ID: <20110706185932.GB3299@albatros> (raw)
In-Reply-To: <CA+55aFyfjG1h2zkkGai_VPM8p5bhWhvNXs1HvuWMgxv4RSywYw@mail.gmail.com>
On Wed, Jul 06, 2011 at 11:01 -0700, Linus Torvalds wrote:
> My reaction is: "let's just remote the crazy check from set_user()
> entirely".
Honestly, I didn't expect such a positive reaction from you in the first
reply :)
> The whole point of RLIMIT_NPROC is to avoid fork-bombs.
It is also used in cases where there is implicit or explicit limit on
some other resource per process leading to the global limit of
RLIMIT_NPROC*X. The most obvious case of X is RLIMIT_AS.
Purely pragmatic approach is introducing the check in execve() to
heuristically limit the number of user processes. If the program uses
PAM to register a user session, maxlogins from pam_limits is the Right
Way. But many programs simply don't use PAM because of the performance
issues. E.g. apache doesn't use PAM. On a shared web hosting this is a
real issue.
In -ow patch execve() checked for the exceeded RLIMIT_NPROC, which
effectively solved Apache's problem.
...and execve() error handling is hard to miss ;-)
> 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.
There are checks only in copy_process() and set_user().
Thanks,
--
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
next prev parent reply other threads:[~2011-07-06 18:59 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-12 13:09 RLIMIT_NPROC check in set_user() Vasiliy Kulikov
2011-07-06 17:36 ` Vasiliy Kulikov
2011-07-06 18:01 ` Linus Torvalds
2011-07-06 18:59 ` Vasiliy Kulikov [this message]
2011-07-07 7:56 ` [kernel-hardening] " Vasiliy Kulikov
2011-07-07 8:19 ` Vasiliy Kulikov
2011-07-12 13:27 ` [PATCH] move RLIMIT_NPROC check from set_user() to do_execve_common() Vasiliy Kulikov
2011-07-12 21:16 ` Linus Torvalds
2011-07-12 23:14 ` NeilBrown
2011-07-13 6:31 ` Solar Designer
2011-07-13 7:06 ` NeilBrown
2011-07-13 20:46 ` Linus Torvalds
2011-07-14 0:11 ` James Morris
2011-07-14 1:27 ` NeilBrown
2011-07-14 15:06 ` Solar Designer
2011-07-15 3:30 ` NeilBrown
2011-07-15 5:35 ` Willy Tarreau
2011-07-15 6:31 ` [kernel-hardening] " Vasiliy Kulikov
2011-07-15 7:06 ` NeilBrown
2011-07-15 7:38 ` Vasiliy Kulikov
2011-07-15 13:04 ` Solar Designer
2011-07-15 13:58 ` [kernel-hardening] " Stephen Smalley
2011-07-15 15:26 ` Vasiliy Kulikov
2011-07-15 19:54 ` Stephen Smalley
2011-07-21 4:09 ` NeilBrown
2011-07-21 12:48 ` Solar Designer
2011-07-21 18:21 ` Linus Torvalds
2011-07-21 19:39 ` [kernel-hardening] " Solar Designer
2011-07-25 17:14 ` Vasiliy Kulikov
2011-07-25 23:40 ` [kernel-hardening] " Solar Designer
2011-07-26 0:47 ` NeilBrown
2011-07-26 1:16 ` Solar Designer
2011-07-26 4:11 ` NeilBrown
2011-07-26 14:48 ` [patch v2] " Vasiliy Kulikov
2011-07-27 2:15 ` NeilBrown
2011-07-29 7:07 ` [kernel-hardening] " Vasiliy Kulikov
2011-07-29 8:06 ` Vasiliy Kulikov
2011-07-29 8:11 ` [patch v3] " Vasiliy Kulikov
2011-07-29 8:17 ` James Morris
2011-07-14 1:30 ` [PATCH] " KOSAKI Motohiro
2011-07-13 5:36 ` KOSAKI Motohiro
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