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![Jann Horn](/assets/img/avatar_default.png)
find_timens_vvar_page() is not architecture-specific, as can be seen from how all five per-architecture versions of it are the same. (arm64, powerpc and riscv are exactly the same; x86 and s390 have two characters difference inside a comment, less blank lines, and mark the !CONFIG_TIME_NS version as inline.) Refactor the five copies into a central copy in kernel/time/namespace.c. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20221130115320.2918447-1-jannh@google.com
485 lines
11 KiB
C
485 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Author: Andrei Vagin <avagin@openvz.org>
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* Author: Dmitry Safonov <dima@arista.com>
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*/
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#include <linux/time_namespace.h>
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#include <linux/user_namespace.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/task.h>
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#include <linux/clocksource.h>
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#include <linux/seq_file.h>
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#include <linux/proc_ns.h>
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#include <linux/export.h>
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#include <linux/time.h>
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#include <linux/slab.h>
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#include <linux/cred.h>
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#include <linux/err.h>
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#include <linux/mm.h>
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#include <vdso/datapage.h>
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ktime_t do_timens_ktime_to_host(clockid_t clockid, ktime_t tim,
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struct timens_offsets *ns_offsets)
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{
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ktime_t offset;
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switch (clockid) {
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case CLOCK_MONOTONIC:
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offset = timespec64_to_ktime(ns_offsets->monotonic);
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break;
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case CLOCK_BOOTTIME:
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case CLOCK_BOOTTIME_ALARM:
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offset = timespec64_to_ktime(ns_offsets->boottime);
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break;
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default:
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return tim;
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}
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/*
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* Check that @tim value is in [offset, KTIME_MAX + offset]
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* and subtract offset.
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*/
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if (tim < offset) {
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/*
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* User can specify @tim *absolute* value - if it's lesser than
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* the time namespace's offset - it's already expired.
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*/
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tim = 0;
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} else {
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tim = ktime_sub(tim, offset);
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if (unlikely(tim > KTIME_MAX))
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tim = KTIME_MAX;
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}
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return tim;
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}
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static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
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{
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return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
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}
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static void dec_time_namespaces(struct ucounts *ucounts)
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{
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dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
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}
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/**
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* clone_time_ns - Clone a time namespace
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* @user_ns: User namespace which owns a new namespace.
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* @old_ns: Namespace to clone
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*
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* Clone @old_ns and set the clone refcount to 1
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*
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* Return: The new namespace or ERR_PTR.
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*/
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static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
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struct time_namespace *old_ns)
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{
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struct time_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_time_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(*ns), GFP_KERNEL_ACCOUNT);
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if (!ns)
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goto fail_dec;
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refcount_set(&ns->ns.count, 1);
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ns->vvar_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
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if (!ns->vvar_page)
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goto fail_free;
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err = ns_alloc_inum(&ns->ns);
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if (err)
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goto fail_free_page;
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ns->ucounts = ucounts;
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ns->ns.ops = &timens_operations;
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ns->user_ns = get_user_ns(user_ns);
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ns->offsets = old_ns->offsets;
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ns->frozen_offsets = false;
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return ns;
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fail_free_page:
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__free_page(ns->vvar_page);
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fail_free:
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kfree(ns);
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fail_dec:
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dec_time_namespaces(ucounts);
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fail:
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return ERR_PTR(err);
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}
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/**
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* copy_time_ns - Create timens_for_children from @old_ns
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* @flags: Cloning flags
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* @user_ns: User namespace which owns a new namespace.
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* @old_ns: Namespace to clone
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*
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* If CLONE_NEWTIME specified in @flags, creates a new timens_for_children;
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* adds a refcounter to @old_ns otherwise.
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*
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* Return: timens_for_children namespace or ERR_PTR.
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*/
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struct time_namespace *copy_time_ns(unsigned long flags,
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struct user_namespace *user_ns, struct time_namespace *old_ns)
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{
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if (!(flags & CLONE_NEWTIME))
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return get_time_ns(old_ns);
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return clone_time_ns(user_ns, old_ns);
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}
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static struct timens_offset offset_from_ts(struct timespec64 off)
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{
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struct timens_offset ret;
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ret.sec = off.tv_sec;
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ret.nsec = off.tv_nsec;
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return ret;
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}
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/*
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* A time namespace VVAR page has the same layout as the VVAR page which
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* contains the system wide VDSO data.
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*
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* For a normal task the VVAR pages are installed in the normal ordering:
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* VVAR
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* PVCLOCK
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* HVCLOCK
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* TIMENS <- Not really required
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*
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* Now for a timens task the pages are installed in the following order:
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* TIMENS
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* PVCLOCK
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* HVCLOCK
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* VVAR
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*
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* The check for vdso_data->clock_mode is in the unlikely path of
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* the seq begin magic. So for the non-timens case most of the time
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* 'seq' is even, so the branch is not taken.
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*
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* If 'seq' is odd, i.e. a concurrent update is in progress, the extra check
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* for vdso_data->clock_mode is a non-issue. The task is spin waiting for the
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* update to finish and for 'seq' to become even anyway.
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*
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* Timens page has vdso_data->clock_mode set to VDSO_CLOCKMODE_TIMENS which
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* enforces the time namespace handling path.
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*/
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static void timens_setup_vdso_data(struct vdso_data *vdata,
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struct time_namespace *ns)
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{
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struct timens_offset *offset = vdata->offset;
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struct timens_offset monotonic = offset_from_ts(ns->offsets.monotonic);
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struct timens_offset boottime = offset_from_ts(ns->offsets.boottime);
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vdata->seq = 1;
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vdata->clock_mode = VDSO_CLOCKMODE_TIMENS;
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offset[CLOCK_MONOTONIC] = monotonic;
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offset[CLOCK_MONOTONIC_RAW] = monotonic;
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offset[CLOCK_MONOTONIC_COARSE] = monotonic;
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offset[CLOCK_BOOTTIME] = boottime;
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offset[CLOCK_BOOTTIME_ALARM] = boottime;
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}
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struct page *find_timens_vvar_page(struct vm_area_struct *vma)
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{
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if (likely(vma->vm_mm == current->mm))
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return current->nsproxy->time_ns->vvar_page;
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/*
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* VM_PFNMAP | VM_IO protect .fault() handler from being called
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* through interfaces like /proc/$pid/mem or
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* process_vm_{readv,writev}() as long as there's no .access()
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* in special_mapping_vmops().
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* For more details check_vma_flags() and __access_remote_vm()
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*/
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WARN(1, "vvar_page accessed remotely");
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return NULL;
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}
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/*
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* Protects possibly multiple offsets writers racing each other
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* and tasks entering the namespace.
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*/
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static DEFINE_MUTEX(offset_lock);
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static void timens_set_vvar_page(struct task_struct *task,
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struct time_namespace *ns)
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{
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struct vdso_data *vdata;
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unsigned int i;
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if (ns == &init_time_ns)
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return;
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/* Fast-path, taken by every task in namespace except the first. */
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if (likely(ns->frozen_offsets))
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return;
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mutex_lock(&offset_lock);
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/* Nothing to-do: vvar_page has been already initialized. */
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if (ns->frozen_offsets)
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goto out;
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ns->frozen_offsets = true;
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vdata = arch_get_vdso_data(page_address(ns->vvar_page));
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for (i = 0; i < CS_BASES; i++)
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timens_setup_vdso_data(&vdata[i], ns);
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out:
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mutex_unlock(&offset_lock);
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}
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void free_time_ns(struct time_namespace *ns)
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{
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dec_time_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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__free_page(ns->vvar_page);
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kfree(ns);
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}
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static struct time_namespace *to_time_ns(struct ns_common *ns)
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{
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return container_of(ns, struct time_namespace, ns);
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}
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static struct ns_common *timens_get(struct task_struct *task)
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{
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struct time_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 = nsproxy->time_ns;
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get_time_ns(ns);
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}
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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 struct ns_common *timens_for_children_get(struct task_struct *task)
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{
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struct time_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 = nsproxy->time_ns_for_children;
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get_time_ns(ns);
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}
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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 timens_put(struct ns_common *ns)
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{
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put_time_ns(to_time_ns(ns));
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}
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void timens_commit(struct task_struct *tsk, struct time_namespace *ns)
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{
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timens_set_vvar_page(tsk, ns);
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vdso_join_timens(tsk, ns);
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}
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static int timens_install(struct nsset *nsset, struct ns_common *new)
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{
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struct nsproxy *nsproxy = nsset->nsproxy;
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struct time_namespace *ns = to_time_ns(new);
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if (!current_is_single_threaded())
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return -EUSERS;
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if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
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!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
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return -EPERM;
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get_time_ns(ns);
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put_time_ns(nsproxy->time_ns);
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nsproxy->time_ns = ns;
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get_time_ns(ns);
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put_time_ns(nsproxy->time_ns_for_children);
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nsproxy->time_ns_for_children = ns;
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return 0;
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}
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void timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
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{
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struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
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struct time_namespace *ns = to_time_ns(nsc);
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/* create_new_namespaces() already incremented the ref counter */
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if (nsproxy->time_ns == nsproxy->time_ns_for_children)
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return;
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get_time_ns(ns);
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put_time_ns(nsproxy->time_ns);
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nsproxy->time_ns = ns;
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timens_commit(tsk, ns);
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}
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static struct user_namespace *timens_owner(struct ns_common *ns)
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{
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return to_time_ns(ns)->user_ns;
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}
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static void show_offset(struct seq_file *m, int clockid, struct timespec64 *ts)
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{
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char *clock;
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switch (clockid) {
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case CLOCK_BOOTTIME:
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clock = "boottime";
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break;
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case CLOCK_MONOTONIC:
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clock = "monotonic";
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break;
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default:
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clock = "unknown";
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break;
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}
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seq_printf(m, "%-10s %10lld %9ld\n", clock, ts->tv_sec, ts->tv_nsec);
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}
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void proc_timens_show_offsets(struct task_struct *p, struct seq_file *m)
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{
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struct ns_common *ns;
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struct time_namespace *time_ns;
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ns = timens_for_children_get(p);
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if (!ns)
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return;
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time_ns = to_time_ns(ns);
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show_offset(m, CLOCK_MONOTONIC, &time_ns->offsets.monotonic);
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show_offset(m, CLOCK_BOOTTIME, &time_ns->offsets.boottime);
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put_time_ns(time_ns);
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}
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int proc_timens_set_offset(struct file *file, struct task_struct *p,
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struct proc_timens_offset *offsets, int noffsets)
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{
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struct ns_common *ns;
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struct time_namespace *time_ns;
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struct timespec64 tp;
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int i, err;
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ns = timens_for_children_get(p);
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if (!ns)
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return -ESRCH;
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time_ns = to_time_ns(ns);
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if (!file_ns_capable(file, time_ns->user_ns, CAP_SYS_TIME)) {
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put_time_ns(time_ns);
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return -EPERM;
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}
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for (i = 0; i < noffsets; i++) {
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struct proc_timens_offset *off = &offsets[i];
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switch (off->clockid) {
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case CLOCK_MONOTONIC:
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ktime_get_ts64(&tp);
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break;
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case CLOCK_BOOTTIME:
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ktime_get_boottime_ts64(&tp);
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break;
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default:
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err = -EINVAL;
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goto out;
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}
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err = -ERANGE;
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if (off->val.tv_sec > KTIME_SEC_MAX ||
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off->val.tv_sec < -KTIME_SEC_MAX)
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goto out;
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tp = timespec64_add(tp, off->val);
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/*
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* KTIME_SEC_MAX is divided by 2 to be sure that KTIME_MAX is
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* still unreachable.
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*/
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if (tp.tv_sec < 0 || tp.tv_sec > KTIME_SEC_MAX / 2)
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goto out;
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}
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mutex_lock(&offset_lock);
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if (time_ns->frozen_offsets) {
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err = -EACCES;
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goto out_unlock;
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}
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err = 0;
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/* Don't report errors after this line */
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for (i = 0; i < noffsets; i++) {
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struct proc_timens_offset *off = &offsets[i];
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struct timespec64 *offset = NULL;
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switch (off->clockid) {
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case CLOCK_MONOTONIC:
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offset = &time_ns->offsets.monotonic;
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break;
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case CLOCK_BOOTTIME:
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offset = &time_ns->offsets.boottime;
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break;
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}
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*offset = off->val;
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}
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out_unlock:
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mutex_unlock(&offset_lock);
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out:
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put_time_ns(time_ns);
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return err;
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}
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const struct proc_ns_operations timens_operations = {
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.name = "time",
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.type = CLONE_NEWTIME,
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.get = timens_get,
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.put = timens_put,
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.install = timens_install,
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.owner = timens_owner,
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};
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const struct proc_ns_operations timens_for_children_operations = {
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.name = "time_for_children",
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.real_ns_name = "time",
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.type = CLONE_NEWTIME,
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.get = timens_for_children_get,
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.put = timens_put,
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.install = timens_install,
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.owner = timens_owner,
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};
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struct time_namespace init_time_ns = {
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.ns.count = REFCOUNT_INIT(3),
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.user_ns = &init_user_ns,
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.ns.inum = PROC_TIME_INIT_INO,
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.ns.ops = &timens_operations,
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.frozen_offsets = true,
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};
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