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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 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1788172082605998195 X-GMAIL-MSGID: 1788172082605998195 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 Link: https://lkml.kernel.org/r/e2d84d3ec0172cfff759e6065da84ce0cc2736f8.1663756794.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" static int proc_ipc_dointvec_minmax_orphans(struct ctl_table *table, int write, @@ -190,25 +191,57 @@ static int set_is_seen(struct ctl_table_set *set) return ¤t->nsproxy->ipc_ns->ipc_set == set; } +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 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; + struct ipc_namespace *ns = + container_of(head->set, struct ipc_namespace, ipc_set); 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; + 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 >>= 6; + + else if (in_egroup_p(ns_root_gid)) + mode >>= 3; + } + + mode &= 7; + + return (mode << 6) | (mode << 3) | mode; } 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)