From: Willy Tarreau <w@1wt.eu>
To: Andy Lutomirski <luto@kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
linux-api@vger.kernel.org,
"Etienne Dechamps" <etienne@edechamps.fr>,
"Alexey Gladkov" <legion@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Shuah Khan" <shuah@kernel.org>,
"Christian Brauner" <brauner@kernel.org>,
"Solar Designer" <solar@openwall.com>,
"Ran Xiaokai" <ran.xiaokai@zte.com.cn>,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
"Linux Containers" <containers@lists.linux-foundation.org>,
"Michal Koutný" <mkoutny@suse.com>,
security@kernel.org, "Neil Brown" <neilb@cse.unsw.edu.au>,
NeilBrown <neilb@suse.de>, "Serge E. Hallyn" <serge@hallyn.com>,
"Jann Horn" <jannh@google.com>
Subject: Re: How should rlimits, suid exec, and capabilities interact?
Date: Wed, 23 Feb 2022 22:28:39 +0100 [thread overview]
Message-ID: <20220223212839.GA12121@1wt.eu> (raw)
In-Reply-To: <CALCETrVh8Xu3VJzseWEJZ+ryy5WANyJg+j4=hFaVFebzSu_TgQ@mail.gmail.com>
Hi Andy,
On Wed, Feb 23, 2022 at 11:44:51AM -0800, Andy Lutomirski wrote:
> On Wed, Feb 23, 2022 at 10:00 AM Eric W. Biederman
> <ebiederm@xmission.com> wrote:
> >
> >
> > [CC'd the security list because I really don't know who the right people
> > are to drag into this discussion]
> >
> > While looking at some issues that have cropped up with making it so
> > that RLIMIT_NPROC cannot be escaped by creating a user namespace I have
> > stumbled upon a very old issue of how rlimits and suid exec interact
> > poorly.
>
> Once upon a time, these resource limits were effectively the only way
> to control memory consumption and consumption of historically limited
> resources like processes. (The scheduler used to have serious issues
> with too many processes -- this is not so true any more. And without
> cgroups, too many processes could use too much CPU collectively.)
> This all worked pretty poorly. Now we have cgroups, fancy memory
> accounting, etc. So I'm wondering if NPROC is even useful anymore. I
> don't have a brilliant idea of how to deprecate it, but I think it
> wouldn't be entirely nuts to take it much less seriously and maybe
> even eventually get rid of it.
>
> I doubt there is much existing userspace that would break if a
> previously failing fork() started succeeding.
I strongly disagree. I've been using it for a long time as a security
measure. Setting NPROC to 0 after daemonizing remains a particularly
effective and portable method to mitigate the possible consequences of
an in-process intrusion. While I wouldn't care about approximate non-zero
values, for me it would be a significant security regression to drop the
inability to fork() when the limit is zero. Thus at least I do want to
keep that feature when NPROC is zero.
Willy
next prev parent reply other threads:[~2022-02-23 21:29 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 12:17 [RFC PATCH 0/6] RLIMIT_NPROC in ucounts fixups Michal Koutný
2022-02-07 12:17 ` [RFC PATCH 1/6] set_user: Perform RLIMIT_NPROC capability check against new user credentials Michal Koutný
2022-02-10 1:14 ` Solar Designer
2022-02-10 1:57 ` Eric W. Biederman
2022-02-11 20:32 ` Eric W. Biederman
2022-02-12 22:14 ` Solar Designer
2022-02-15 11:55 ` Michal Koutný
2022-02-07 12:17 ` [RFC PATCH 2/6] set*uid: Check RLIMIT_PROC against new credentials Michal Koutný
2022-02-07 12:17 ` [RFC PATCH 3/6] cred: Count tasks by their real uid into RLIMIT_NPROC Michal Koutný
2022-02-07 12:17 ` [RFC PATCH 4/6] ucounts: Allow root to override RLIMIT_NPROC Michal Koutný
2022-02-10 0:21 ` Eric W. Biederman
2022-02-07 12:17 ` [RFC PATCH 5/6] selftests: Challenge RLIMIT_NPROC in user namespaces Michal Koutný
2022-02-10 1:22 ` Shuah Khan
2022-02-15 9:45 ` Michal Koutný
2022-02-07 12:18 ` [RFC PATCH 6/6] selftests: Test RLIMIT_NPROC in clone-created " Michal Koutný
2022-02-10 1:25 ` Shuah Khan
2022-02-15 9:34 ` Michal Koutný
2022-02-08 13:54 ` [RFC PATCH 0/6] RLIMIT_NPROC in ucounts fixups Eric W. Biederman
2022-02-11 2:01 ` [PATCH 0/8] ucounts: RLIMIT_NPROC fixes Eric W. Biederman
2022-02-11 2:13 ` [PATCH 1/8] ucounts: Fix RLIMIT_NPROC regression Eric W. Biederman
2022-02-14 18:37 ` Michal Koutný
2022-02-16 15:22 ` Eric W. Biederman
2022-02-11 2:13 ` [PATCH 2/8] ucounts: Fix set_cred_ucounts Eric W. Biederman
2022-02-15 11:10 ` Michal Koutný
2022-02-11 2:13 ` [PATCH 3/8] ucounts: Fix and simplify RLIMIT_NPROC handling during setuid()+execve Eric W. Biederman
2022-02-12 23:17 ` Solar Designer
2022-02-14 15:10 ` Eric W. Biederman
2022-02-14 17:43 ` Eric W. Biederman
2022-02-15 10:25 ` Michal Koutný
2022-02-16 15:35 ` Eric W. Biederman
2022-02-11 2:13 ` [PATCH 4/8] ucounts: Only except the root user in init_user_ns from RLIMIT_NPROC Eric W. Biederman
2022-02-15 10:54 ` Michal Koutný
2022-02-16 15:41 ` Eric W. Biederman
2022-02-11 2:13 ` [PATCH 5/8] ucounts: Handle wrapping in is_ucounts_overlimit Eric W. Biederman
2022-02-12 22:36 ` Solar Designer
2022-02-14 15:23 ` Eric W. Biederman
2022-02-14 15:23 ` Eric W. Biederman
2022-02-15 11:25 ` Michal Koutný
2022-02-14 17:16 ` David Laight
2022-02-11 2:13 ` [PATCH 6/8] ucounts: Handle inc_rlimit_ucounts wrapping in fork Eric W. Biederman
2022-02-11 11:34 ` Alexey Gladkov
2022-02-11 17:50 ` Eric W. Biederman
2022-02-11 18:32 ` Shuah Khan
2022-02-11 18:40 ` Alexey Gladkov
2022-02-11 19:56 ` Eric W. Biederman
2022-02-11 2:13 ` [PATCH 7/8] rlimit: For RLIMIT_NPROC test the child not the parent for capabilites Eric W. Biederman
2022-02-11 2:13 ` [PATCH 8/8] ucounts: Use the same code to enforce RLIMIT_NPROC in fork and exec Eric W. Biederman
2022-02-11 18:22 ` [PATCH 0/8] ucounts: RLIMIT_NPROC fixes Shuah Khan
2022-02-11 19:23 ` Eric W. Biederman
2022-02-15 11:37 ` Michal Koutný
2022-02-16 15:56 ` [PATCH v2 0/5] " Eric W. Biederman
2022-02-16 15:58 ` [PATCH v2 1/5] rlimit: Fix RLIMIT_NPROC enforcement failure caused by capability calls in set_user Eric W. Biederman
2022-02-16 17:42 ` Solar Designer
2022-02-16 15:58 ` [PATCH v2 2/5] ucounts: Enforce RLIMIT_NPROC not RLIMIT_NPROC+1 Eric W. Biederman
2022-02-16 15:58 ` [PATCH v2 3/5] ucounts: Base set_cred_ucounts changes on the real user Eric W. Biederman
2022-02-16 15:58 ` [PATCH v2 4/5] ucounts: Move RLIMIT_NPROC handling after set_user Eric W. Biederman
2022-02-16 15:58 ` [PATCH v2 5/5] ucounts: Handle wrapping in is_ucounts_overlimit Eric W. Biederman
2022-02-16 17:28 ` Shuah Khan
2022-02-18 15:34 ` [GIT PULL] ucounts: RLIMIT_NPROC fixes for v5.17 Eric W. Biederman
2022-02-20 19:05 ` pr-tracker-bot
2022-03-03 0:12 ` [GIT PULL] ucounts: Regression fix " Eric W. Biederman
2022-03-03 0:30 ` pr-tracker-bot
2022-02-12 15:32 ` [RFC PATCH 0/6] RLIMIT_NPROC in ucounts fixups Etienne Dechamps
2022-02-15 10:11 ` Michal Koutný
2022-02-23 0:57 ` Eric W. Biederman
2022-02-23 18:00 ` How should rlimits, suid exec, and capabilities interact? Eric W. Biederman
2022-02-23 19:44 ` Andy Lutomirski
2022-02-23 21:28 ` Willy Tarreau [this message]
2022-02-23 19:50 ` Linus Torvalds
2022-02-24 1:24 ` Eric W. Biederman
2022-02-24 1:41 ` Linus Torvalds
2022-02-24 2:12 ` Eric W. Biederman
2022-02-24 15:41 ` [PATCH] ucounts: Fix systemd LimigtNPROC with private users regression Eric W. Biederman
2022-02-24 16:28 ` Kees Cook
2022-02-24 18:53 ` Michal Koutný
2022-02-25 0:29 ` Eric W. Biederman
2022-02-24 3:00 ` How should rlimits, suid exec, and capabilities interact? David Laight
2022-02-24 1:32 ` Eric W. Biederman
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