From: "Eric W. Biederman" <ebiederm@xmission.com>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: linux-kernel@vger.kernel.org, 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>,
containers@lists.linux-foundation.org, stable@vger.kernel.org
Subject: Re: [PATCH 4/8] ucounts: Only except the root user in init_user_ns from RLIMIT_NPROC
Date: Wed, 16 Feb 2022 09:41:44 -0600 [thread overview]
Message-ID: <87ee42kedj.fsf@email.froward.int.ebiederm.org> (raw)
In-Reply-To: <20220215105442.GF21589@blackbody.suse.cz> ("Michal =?utf-8?Q?Koutn=C3=BD=22's?= message of "Tue, 15 Feb 2022 11:54:42 +0100")
Michal Koutný <mkoutny@suse.com> writes:
> On Thu, Feb 10, 2022 at 08:13:20PM -0600, "Eric W. Biederman" <ebiederm@xmission.com> wrote:
>> @@ -1881,7 +1881,7 @@ static int do_execveat_common(int fd, struct filename *filename,
> [...]
>> - (current_user() != INIT_USER) &&
>> + (current_ucounts() != &init_ucounts) &&
> [...]
>> @@ -2027,7 +2027,7 @@ static __latent_entropy struct task_struct *copy_process(
> [...]
>> - if (p->real_cred->user != INIT_USER &&
>> + if ((task_ucounts(p) != &init_ucounts) &&
>
> These substitutions make sense to me.
>
>> !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
>> goto bad_fork_cleanup_count;
>> }
>> diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
>> index 6b2e3ca7ee99..f0c04073403d 100644
>> --- a/kernel/user_namespace.c
>> +++ b/kernel/user_namespace.c
>> @@ -123,6 +123,8 @@ int create_user_ns(struct cred *new)
>> ns->ucount_max[i] = INT_MAX;
>> }
>> set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC));
>> + if (new->ucounts == &init_ucounts)
>> + set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_NPROC, RLIMIT_INFINITY);
>> set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
>> set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
>> set_rlimit_ucount_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
>
> First, I wanted to object this double fork_init() but I realized it's
> relevant for newly created user_ns.
>
> Second, I think new->ucounts would be correct at this point and the
> check should be
>
>> if (ucounts == &init_ucounts)
>
> i.e. before set_cred_ucounts() new->ucounts may not be correct.
>
> I'd suggest also a comment in the create_user_ns() explaining the
> reason is to exempt global root from RLIMINT_NRPOC also indirectly via
> descendant user_nss.
Yes.
This one got culled from my next version of the patchset as it is not
conservative enough. I think it is probably the right general
direction.
On further reflection I am not convinced that it makes sense to test
user or ucounts. They are really not fields designed to support
permission checks.
I think if we want to exempt the root user's children from the root
users rlimit using the second set_rlimit_ucount_max is the way to go.
Someone filed a bug that strongly suggests that we want the second
set_rlimit_ucount_max:
https://bugzilla.kernel.org/show_bug.cgi?id=215596
I am still trying to understand that case.
Eric
next prev parent reply other threads:[~2022-02-16 15:42 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 [this message]
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
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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