From nobody Tue Dec 16 11:48:22 2025 Received: from us-smtp-delivery-44.mimecast.com (us-smtp-delivery-44.mimecast.com [207.211.30.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CDBB7179A5 for ; Mon, 15 Jan 2024 15:49:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=kernel.org Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-577-w6Of273vPOui2F9i1TlWMA-1; Mon, 15 Jan 2024 10:47:13 -0500 X-MC-Unique: w6Of273vPOui2F9i1TlWMA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B82B482DFE7; Mon, 15 Jan 2024 15:47:12 +0000 (UTC) Received: from localhost.redhat.com (unknown [10.45.226.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C7723C25; Mon, 15 Jan 2024 15:47:11 +0000 (UTC) From: Alexey Gladkov To: LKML , Linux Containers Cc: Andrew Morton , Christian Brauner , "Eric W . Biederman" , Joel Granados , Kees Cook , Luis Chamberlain , Manfred Spraul Subject: [RESEND PATCH v3 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace Date: Mon, 15 Jan 2024 15:46:41 +0000 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Content-Type: text/plain; charset="utf-8" Rootless containers are not allowed to modify kernel IPC parameters. All default limits are set to such high values that in fact there are no limits at all. All limits are not inherited and are initialized to default values when a new ipc_namespace is created. For new ipc_namespace: size_t ipc_ns.shm_ctlmax =3D SHMMAX; // (ULONG_MAX - (1UL << 24)) size_t ipc_ns.shm_ctlall =3D SHMALL; // (ULONG_MAX - (1UL << 24)) int ipc_ns.shm_ctlmni =3D IPCMNI; // (1 << 15) int ipc_ns.shm_rmid_forced =3D 0; unsigned int ipc_ns.msg_ctlmax =3D MSGMAX; // 8192 unsigned int ipc_ns.msg_ctlmni =3D MSGMNI; // 32000 unsigned int ipc_ns.msg_ctlmnb =3D MSGMNB; // 16384 The shm_tot (total amount of shared pages) has also ceased to be global, it is located in ipc_namespace and is not inherited from anywhere. In such conditions, it cannot be said that these limits limit anything. The real limiter for them is cgroups. If we allow rootless containers to change these parameters, then it can only be reduced. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/e2d84d3ec0172cfff759e6065da84ce0cc2736f8.16= 63756794.git.legion@kernel.org Signed-off-by: Eric W. Biederman --- ipc/ipc_sysctl.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-) diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index 8c62e443f78b..01c4a50d22b2 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -14,6 +14,7 @@ #include #include #include +#include #include "util.h" =20 static int proc_ipc_dointvec_minmax_orphans(struct ctl_table *table, int w= rite, @@ -190,25 +191,57 @@ static int set_is_seen(struct ctl_table_set *set) return ¤t->nsproxy->ipc_ns->ipc_set =3D=3D set; } =20 +static void ipc_set_ownership(struct ctl_table_header *head, + struct ctl_table *table, + kuid_t *uid, kgid_t *gid) +{ + struct ipc_namespace *ns =3D + container_of(head->set, struct ipc_namespace, ipc_set); + + kuid_t ns_root_uid =3D make_kuid(ns->user_ns, 0); + kgid_t ns_root_gid =3D make_kgid(ns->user_ns, 0); + + *uid =3D uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID; + *gid =3D gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID; +} + static int ipc_permissions(struct ctl_table_header *head, struct ctl_table= *table) { int mode =3D table->mode; =20 #ifdef CONFIG_CHECKPOINT_RESTORE - struct ipc_namespace *ns =3D current->nsproxy->ipc_ns; + struct ipc_namespace *ns =3D + container_of(head->set, struct ipc_namespace, ipc_set); =20 if (((table->data =3D=3D &ns->ids[IPC_SEM_IDS].next_id) || (table->data =3D=3D &ns->ids[IPC_MSG_IDS].next_id) || (table->data =3D=3D &ns->ids[IPC_SHM_IDS].next_id)) && checkpoint_restore_ns_capable(ns->user_ns)) mode =3D 0666; + else #endif - return mode; + { + kuid_t ns_root_uid; + kgid_t ns_root_gid; + + ipc_set_ownership(head, table, &ns_root_uid, &ns_root_gid); + + if (uid_eq(current_euid(), ns_root_uid)) + mode >>=3D 6; + + else if (in_egroup_p(ns_root_gid)) + mode >>=3D 3; + } + + mode &=3D 7; + + return (mode << 6) | (mode << 3) | mode; } =20 static struct ctl_table_root set_root =3D { .lookup =3D set_lookup, .permissions =3D ipc_permissions, + .set_ownership =3D ipc_set_ownership, }; =20 bool setup_ipc_sysctls(struct ipc_namespace *ns) --=20 2.43.0 From nobody Tue Dec 16 11:48:22 2025 Received: from us-smtp-delivery-44.mimecast.com (us-smtp-delivery-44.mimecast.com [205.139.111.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 537A91774C for ; Mon, 15 Jan 2024 15:48:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=kernel.org Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-459-QAkLZRVbNMynMU_EIsS2Bw-1; Mon, 15 Jan 2024 10:47:15 -0500 X-MC-Unique: QAkLZRVbNMynMU_EIsS2Bw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6458C3830084; Mon, 15 Jan 2024 15:47:14 +0000 (UTC) Received: from localhost.redhat.com (unknown [10.45.226.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id EFF293C25; Mon, 15 Jan 2024 15:47:12 +0000 (UTC) From: Alexey Gladkov To: LKML , Linux Containers , linux-doc@vger.kernel.org Cc: Andrew Morton , Christian Brauner , "Eric W . Biederman" , Joel Granados , Kees Cook , Luis Chamberlain , Manfred Spraul Subject: [RESEND PATCH v3 2/3] docs: Add information about ipc sysctls limitations Date: Mon, 15 Jan 2024 15:46:42 +0000 Message-ID: <09e99911071766958af488beb4e8a728a4f12135.1705333426.git.legion@kernel.org> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Content-Type: text/plain; charset="utf-8" After 25b21cb2f6d6 ("[PATCH] IPC namespace core") and 4e9823111bdc ("[PATCH] IPC namespace - shm") the shared memory page count stopped being global and started counting per ipc namespace. The documentation and shmget(2) still says that shmall is a global option. shmget(2): SHMALL System-wide limit on the total amount of shared memory, measured in units of the system page size. On Linux, this limit can be read and modified via /proc/sys/kernel/shmall. I think the changes made in 2006 should be documented. Signed-off-by: Alexey Gladkov Acked-by: "Eric W. Biederman" Link: https://lkml.kernel.org/r/ede20ddf7be48b93e8084c3be2e920841ee1a641.16= 63756794.git.legion@kernel.org Signed-off-by: Eric W. Biederman --- Documentation/admin-guide/sysctl/kernel.rst | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/ad= min-guide/sysctl/kernel.rst index 6584a1f9bfe3..bc578663619d 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -594,6 +594,9 @@ default (``MSGMNB``). ``msgmni`` is the maximum number of IPC queues. 32000 by default (``MSGMNI``). =20 +All of these parameters are set per ipc namespace. The maximum number of b= ytes +in POSIX message queues is limited by ``RLIMIT_MSGQUEUE``. This limit is +respected hierarchically in the each user namespace. =20 msg_next_id, sem_next_id, and shm_next_id (System V IPC) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D @@ -1274,15 +1277,20 @@ are doing anyway :) shmall =3D=3D=3D=3D=3D=3D =20 -This parameter sets the total amount of shared memory pages that -can be used system wide. Hence, ``shmall`` should always be at least -``ceil(shmmax/PAGE_SIZE)``. +This parameter sets the total amount of shared memory pages that can be us= ed +inside ipc namespace. The shared memory pages counting occurs for each ipc +namespace separately and is not inherited. Hence, ``shmall`` should always= be at +least ``ceil(shmmax/PAGE_SIZE)``. =20 If you are not sure what the default ``PAGE_SIZE`` is on your Linux system, you can run the following command:: =20 # getconf PAGE_SIZE =20 +To reduce or disable the ability to allocate shared memory, you must creat= e a +new ipc namespace, set this parameter to the required value and prohibit t= he +creation of a new ipc namespace in the current user namespace or cgroups c= an +be used. =20 shmmax =3D=3D=3D=3D=3D=3D --=20 2.43.0 From nobody Tue Dec 16 11:48:22 2025 Received: from us-smtp-delivery-44.mimecast.com (us-smtp-delivery-44.mimecast.com [207.211.30.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 95BA317757 for ; Mon, 15 Jan 2024 15:48:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=kernel.org Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-107-_RghfqN5O6OKasyAw_gn3g-1; Mon, 15 Jan 2024 10:47:16 -0500 X-MC-Unique: _RghfqN5O6OKasyAw_gn3g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E73FE2825BBF; Mon, 15 Jan 2024 15:47:15 +0000 (UTC) Received: from localhost.redhat.com (unknown [10.45.226.182]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9B36F3C25; Mon, 15 Jan 2024 15:47:14 +0000 (UTC) From: Alexey Gladkov To: LKML , Linux Containers Cc: Andrew Morton , Christian Brauner , "Eric W . Biederman" , Joel Granados , Kees Cook , Luis Chamberlain , Manfred Spraul Subject: [RESEND PATCH v3 3/3] sysctl: Allow to change limits for posix messages queues Date: Mon, 15 Jan 2024 15:46:43 +0000 Message-ID: <6ad67f23d1459a4f4339f74aa73bac0ecf3995e1.1705333426.git.legion@kernel.org> In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 Content-Type: text/plain; charset="utf-8" All parameters of posix messages queues (queues_max/msg_max/msgsize_max) end up being limited by RLIMIT_MSGQUEUE. The code in mqueue_get_inode is where that limiting happens. The RLIMIT_MSGQUEUE is bound to the user namespace and is counted hierarchically. We can allow root in the user namespace to modify the posix messages queues parameters. Signed-off-by: Alexey Gladkov Link: https://lkml.kernel.org/r/7eb21211c8622e91d226e63416b1b93c079f60ee.16= 63756794.git.legion@kernel.org Signed-off-by: Eric W. Biederman --- ipc/mq_sysctl.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c index ebb5ed81c151..21fba3a6edaf 100644 --- a/ipc/mq_sysctl.c +++ b/ipc/mq_sysctl.c @@ -12,6 +12,7 @@ #include #include #include +#include =20 static int msg_max_limit_min =3D MIN_MSGMAX; static int msg_max_limit_max =3D HARD_MSGMAX; @@ -76,8 +77,43 @@ static int set_is_seen(struct ctl_table_set *set) return ¤t->nsproxy->ipc_ns->mq_set =3D=3D set; } =20 +static void mq_set_ownership(struct ctl_table_header *head, + struct ctl_table *table, + kuid_t *uid, kgid_t *gid) +{ + struct ipc_namespace *ns =3D + container_of(head->set, struct ipc_namespace, mq_set); + + kuid_t ns_root_uid =3D make_kuid(ns->user_ns, 0); + kgid_t ns_root_gid =3D make_kgid(ns->user_ns, 0); + + *uid =3D uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID; + *gid =3D gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID; +} + +static int mq_permissions(struct ctl_table_header *head, struct ctl_table = *table) +{ + int mode =3D table->mode; + kuid_t ns_root_uid; + kgid_t ns_root_gid; + + mq_set_ownership(head, table, &ns_root_uid, &ns_root_gid); + + if (uid_eq(current_euid(), ns_root_uid)) + mode >>=3D 6; + + else if (in_egroup_p(ns_root_gid)) + mode >>=3D 3; + + mode &=3D 7; + + return (mode << 6) | (mode << 3) | mode; +} + static struct ctl_table_root set_root =3D { .lookup =3D set_lookup, + .permissions =3D mq_permissions, + .set_ownership =3D mq_set_ownership, }; =20 bool setup_mq_sysctls(struct ipc_namespace *ns) --=20 2.43.0