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![Guillaume Knispel](/assets/img/avatar_default.png)
ipc_findkey() used to scan all objects to look for the wanted key. This is slow when using a high number of keys. This change adds an rhashtable of kern_ipc_perm objects in ipc_ids, so that one lookup cease to be O(n). This change gives a 865% improvement of benchmark reaim.jobs_per_min on a 56 threads Intel(R) Xeon(R) CPU E5-2695 v3 @ 2.30GHz with 256G memory [1] Other (more micro) benchmark results, by the author: On an i5 laptop, the following loop executed right after a reboot took, without and with this change: for (int i = 0, k=0x424242; i < KEYS; ++i) semget(k++, 1, IPC_CREAT | 0600); total total max single max single KEYS without with call without call with 1 3.5 4.9 µs 3.5 4.9 10 7.6 8.6 µs 3.7 4.7 32 16.2 15.9 µs 4.3 5.3 100 72.9 41.8 µs 3.7 4.7 1000 5,630.0 502.0 µs * * 10000 1,340,000.0 7,240.0 µs * * 31900 17,600,000.0 22,200.0 µs * * *: unreliable measure: high variance The duration for a lookup-only usage was obtained by the same loop once the keys are present: total total max single max single KEYS without with call without call with 1 2.1 2.5 µs 2.1 2.5 10 4.5 4.8 µs 2.2 2.3 32 13.0 10.8 µs 2.3 2.8 100 82.9 25.1 µs * 2.3 1000 5,780.0 217.0 µs * * 10000 1,470,000.0 2,520.0 µs * * 31900 17,400,000.0 7,810.0 µs * * Finally, executing each semget() in a new process gave, when still summing only the durations of these syscalls: creation: total total KEYS without with 1 3.7 5.0 µs 10 32.9 36.7 µs 32 125.0 109.0 µs 100 523.0 353.0 µs 1000 20,300.0 3,280.0 µs 10000 2,470,000.0 46,700.0 µs 31900 27,800,000.0 219,000.0 µs lookup-only: total total KEYS without with 1 2.5 2.7 µs 10 25.4 24.4 µs 32 106.0 72.6 µs 100 591.0 352.0 µs 1000 22,400.0 2,250.0 µs 10000 2,510,000.0 25,700.0 µs 31900 28,200,000.0 115,000.0 µs [1] http://lkml.kernel.org/r/20170814060507.GE23258@yexl-desktop Link: http://lkml.kernel.org/r/20170815194954.ck32ta2z35yuzpwp@debix Signed-off-by: Guillaume Knispel <guillaume.knispel@supersonicimagine.com> Reviewed-by: Marc Pardo <marc.pardo@supersonicimagine.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Kees Cook <keescook@chromium.org> Cc: Manfred Spraul <manfred@colorfullife.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Serge Hallyn <serge@hallyn.com> Cc: Andrey Vagin <avagin@openvz.org> Cc: Guillaume Knispel <guillaume.knispel@supersonicimagine.com> Cc: Marc Pardo <marc.pardo@supersonicimagine.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
217 lines
4.8 KiB
C
217 lines
4.8 KiB
C
/*
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* linux/ipc/namespace.c
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* Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
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*/
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#include <linux/ipc.h>
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#include <linux/msg.h>
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#include <linux/ipc_namespace.h>
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#include <linux/rcupdate.h>
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#include <linux/nsproxy.h>
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#include <linux/slab.h>
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#include <linux/cred.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/user_namespace.h>
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#include <linux/proc_ns.h>
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#include <linux/sched/task.h>
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#include "util.h"
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static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
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{
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return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
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}
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static void dec_ipc_namespaces(struct ucounts *ucounts)
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{
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dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
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}
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static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
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struct ipc_namespace *old_ns)
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{
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struct ipc_namespace *ns;
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struct ucounts *ucounts;
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int err;
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err = -ENOSPC;
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ucounts = inc_ipc_namespaces(user_ns);
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if (!ucounts)
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goto fail;
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err = -ENOMEM;
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ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
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if (ns == NULL)
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goto fail_dec;
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err = ns_alloc_inum(&ns->ns);
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if (err)
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goto fail_free;
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ns->ns.ops = &ipcns_operations;
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refcount_set(&ns->count, 1);
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ns->user_ns = get_user_ns(user_ns);
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ns->ucounts = ucounts;
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err = sem_init_ns(ns);
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if (err)
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goto fail_put;
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err = msg_init_ns(ns);
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if (err)
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goto fail_destroy_sem;
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err = shm_init_ns(ns);
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if (err)
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goto fail_destroy_msg;
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err = mq_init_ns(ns);
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if (err)
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goto fail_destroy_shm;
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return ns;
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fail_destroy_shm:
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shm_exit_ns(ns);
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fail_destroy_msg:
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msg_exit_ns(ns);
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fail_destroy_sem:
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sem_exit_ns(ns);
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fail_put:
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put_user_ns(ns->user_ns);
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ns_free_inum(&ns->ns);
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fail_free:
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kfree(ns);
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fail_dec:
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dec_ipc_namespaces(ucounts);
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fail:
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return ERR_PTR(err);
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}
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struct ipc_namespace *copy_ipcs(unsigned long flags,
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struct user_namespace *user_ns, struct ipc_namespace *ns)
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{
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if (!(flags & CLONE_NEWIPC))
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return get_ipc_ns(ns);
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return create_ipc_ns(user_ns, ns);
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}
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/*
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* free_ipcs - free all ipcs of one type
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* @ns: the namespace to remove the ipcs from
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* @ids: the table of ipcs to free
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* @free: the function called to free each individual ipc
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*
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* Called for each kind of ipc when an ipc_namespace exits.
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*/
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void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
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{
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struct kern_ipc_perm *perm;
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int next_id;
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int total, in_use;
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down_write(&ids->rwsem);
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in_use = ids->in_use;
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for (total = 0, next_id = 0; total < in_use; next_id++) {
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perm = idr_find(&ids->ipcs_idr, next_id);
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if (perm == NULL)
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continue;
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rcu_read_lock();
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ipc_lock_object(perm);
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free(ns, perm);
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total++;
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}
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up_write(&ids->rwsem);
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}
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static void free_ipc_ns(struct ipc_namespace *ns)
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{
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sem_exit_ns(ns);
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msg_exit_ns(ns);
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shm_exit_ns(ns);
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dec_ipc_namespaces(ns->ucounts);
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put_user_ns(ns->user_ns);
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ns_free_inum(&ns->ns);
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kfree(ns);
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}
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/*
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* put_ipc_ns - drop a reference to an ipc namespace.
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* @ns: the namespace to put
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*
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* If this is the last task in the namespace exiting, and
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* it is dropping the refcount to 0, then it can race with
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* a task in another ipc namespace but in a mounts namespace
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* which has this ipcns's mqueuefs mounted, doing some action
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* with one of the mqueuefs files. That can raise the refcount.
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* So dropping the refcount, and raising the refcount when
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* accessing it through the VFS, are protected with mq_lock.
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*
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* (Clearly, a task raising the refcount on its own ipc_ns
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* needn't take mq_lock since it can't race with the last task
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* in the ipcns exiting).
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*/
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void put_ipc_ns(struct ipc_namespace *ns)
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{
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if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
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mq_clear_sbinfo(ns);
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spin_unlock(&mq_lock);
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mq_put_mnt(ns);
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free_ipc_ns(ns);
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}
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}
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static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
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{
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return container_of(ns, struct ipc_namespace, ns);
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}
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static struct ns_common *ipcns_get(struct task_struct *task)
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{
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struct ipc_namespace *ns = NULL;
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struct nsproxy *nsproxy;
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task_lock(task);
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nsproxy = task->nsproxy;
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if (nsproxy)
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ns = get_ipc_ns(nsproxy->ipc_ns);
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task_unlock(task);
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return ns ? &ns->ns : NULL;
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}
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static void ipcns_put(struct ns_common *ns)
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{
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return put_ipc_ns(to_ipc_ns(ns));
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}
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static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
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{
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struct ipc_namespace *ns = to_ipc_ns(new);
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if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
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!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
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return -EPERM;
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/* Ditch state from the old ipc namespace */
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exit_sem(current);
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put_ipc_ns(nsproxy->ipc_ns);
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nsproxy->ipc_ns = get_ipc_ns(ns);
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return 0;
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}
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static struct user_namespace *ipcns_owner(struct ns_common *ns)
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{
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return to_ipc_ns(ns)->user_ns;
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}
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const struct proc_ns_operations ipcns_operations = {
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.name = "ipc",
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.type = CLONE_NEWIPC,
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.get = ipcns_get,
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.put = ipcns_put,
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.install = ipcns_install,
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.owner = ipcns_owner,
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};
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