From mboxrd@z Thu Jan 1 00:00:00 1970 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 A222A5391 for ; Tue, 16 Aug 2022 15:45:04 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-648-tlIXQnlMPj-Vw1maJoRJmw-1; Tue, 16 Aug 2022 11:43:53 -0400 X-MC-Unique: tlIXQnlMPj-Vw1maJoRJmw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6970380231E; Tue, 16 Aug 2022 15:43:53 +0000 (UTC) Received: from comp-core-i7-2640m-0182e6.redhat.com (unknown [10.40.208.6]) by smtp.corp.redhat.com (Postfix) with ESMTP id 14B452166B26; Tue, 16 Aug 2022 15:43:51 +0000 (UTC) From: Alexey Gladkov To: LKML , Linux Containers Cc: Andrew Morton , Christian Brauner , "Eric W . Biederman" , Kees Cook , Manfred Spraul Subject: [PATCH v1 1/3] sysctl: Allow change system v ipc sysctls inside ipc namespace Date: Tue, 16 Aug 2022 17:42:43 +0200 Message-Id: <63e9e1ff5f988108ceb663a2fbc23a137b0b4311.1660664258.git.legion@kernel.org> In-Reply-To: References: <87wnc1i2wo.fsf@email.froward.int.ebiederm.org> Precedence: bulk X-Mailing-List: containers@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 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 = SHMMAX; // (ULONG_MAX - (1UL << 24)) size_t ipc_ns.shm_ctlall = SHMALL; // (ULONG_MAX - (1UL << 24)) int ipc_ns.shm_ctlmni = IPCMNI; // (1 << 15) int ipc_ns.shm_rmid_forced = 0; unsigned int ipc_ns.msg_ctlmax = MSGMAX; // 8192 unsigned int ipc_ns.msg_ctlmni = MSGMNI; // 32000 unsigned int ipc_ns.msg_ctlmnb = 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 --- ipc/ipc_sysctl.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c index ef313ecfb53a..87eb1b1e42fa 100644 --- a/ipc/ipc_sysctl.c +++ b/ipc/ipc_sysctl.c @@ -192,23 +192,47 @@ static int set_is_seen(struct ctl_table_set *set) static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table) { - int mode = table->mode; - -#ifdef CONFIG_CHECKPOINT_RESTORE struct ipc_namespace *ns = current->nsproxy->ipc_ns; +#ifdef CONFIG_CHECKPOINT_RESTORE if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) || (table->data == &ns->ids[IPC_MSG_IDS].next_id) || (table->data == &ns->ids[IPC_SHM_IDS].next_id)) && checkpoint_restore_ns_capable(ns->user_ns)) - mode = 0666; + return 0666; #endif - return mode; + if (ns->user_ns != &init_user_ns) { + kuid_t ns_root_uid = make_kuid(ns->user_ns, 0); + kgid_t ns_root_gid = make_kgid(ns->user_ns, 0); + + if (uid_valid(ns_root_uid) && uid_eq(current_euid(), ns_root_uid)) + return table->mode >> 6; + + if (gid_valid(ns_root_gid) && in_egroup_p(ns_root_gid)) + return table->mode >> 3; + } + + return table->mode; +} + +static void ipc_set_ownership(struct ctl_table_header *head, + struct ctl_table *table, + kuid_t *uid, kgid_t *gid) +{ + struct ipc_namespace *ns = + container_of(head->set, struct ipc_namespace, ipc_set); + + kuid_t ns_root_uid = make_kuid(ns->user_ns, 0); + kgid_t ns_root_gid = make_kgid(ns->user_ns, 0); + + *uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID; + *gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID; } static struct ctl_table_root set_root = { .lookup = set_lookup, .permissions = ipc_permissions, + .set_ownership = ipc_set_ownership, }; bool setup_ipc_sysctls(struct ipc_namespace *ns) -- 2.33.4