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Message-ID: <alpine.DEB.2.21.1908151908230.1908@nanos.tec.linutronix.de>
Date: Thu, 15 Aug 2019 19:19:12 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Dmitry Safonov <dima@...sta.com>
cc: linux-kernel@...r.kernel.org,
Dmitry Safonov <0x7f454c46@...il.com>,
Andrei Vagin <avagin@...nvz.org>,
Adrian Reber <adrian@...as.de>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>,
Christian Brauner <christian.brauner@...ntu.com>,
Cyrill Gorcunov <gorcunov@...nvz.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
Oleg Nesterov <oleg@...hat.com>,
Pavel Emelyanov <xemul@...tuozzo.com>,
Shuah Khan <shuah@...nel.org>,
Vincenzo Frascino <vincenzo.frascino@....com>,
containers@...ts.linux-foundation.org, criu@...nvz.org,
linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv6 01/36] ns: Introduce Time Namespace
Dmitry,
On Thu, 15 Aug 2019, Dmitry Safonov wrote:
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 420567d1519a..97b7737f5aba 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12898,6 +12898,8 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
> S: Maintained
> F: fs/timerfd.c
> F: include/linux/timer*
> +F: include/linux/time_namespace.h
> +F: kernel/time_namespace.c
Shouldn't this be kernel/time/namespace.c so all that stuff is lumped
together. No strong opinion though.
> +++ b/kernel/time_namespace.c
> +static struct ucounts *inc_time_namespaces(struct user_namespace *ns)
> +{
> + return inc_ucount(ns, current_euid(), UCOUNT_TIME_NAMESPACES);
> +}
> +
> +static void dec_time_namespaces(struct ucounts *ucounts)
> +{
> + dec_ucount(ucounts, UCOUNT_TIME_NAMESPACES);
> +}
> +
> +static struct time_namespace *create_time_ns(void)
> +{
> + struct time_namespace *time_ns;
> +
> + time_ns = kmalloc(sizeof(struct time_namespace), GFP_KERNEL);
Shouldn't this use kzalloc()? There are tons of members in that struct.
> + if (time_ns) {
> + kref_init(&time_ns->kref);
> + time_ns->initialized = false;
And you spare this one.
> + }
> + return time_ns;
> +}
> +
> +/*
> + * Clone a new ns copying @old_ns, setting refcount to 1
> + * @old_ns: namespace to clone
> + * Return the new ns or ERR_PTR.
If you use kernel-doc style then please use te proper syntax
/*
* clone_time_ns - Clone a time namespace
* @old_ns: Namespace to clone
*
* Clone @old_ns and set the clone refcount to 1
*
* Return: The new namespace or ERR_PTR.
*/
> + */
> +static struct time_namespace *clone_time_ns(struct user_namespace *user_ns,
> + struct time_namespace *old_ns)
> +{
> + struct time_namespace *ns;
> + struct ucounts *ucounts;
> + int err;
> +
> + err = -ENOSPC;
> + ucounts = inc_time_namespaces(user_ns);
> + if (!ucounts)
> + goto fail;
> +
> + err = -ENOMEM;
> + ns = create_time_ns();
> + if (!ns)
> + goto fail_dec;
> +
> + err = ns_alloc_inum(&ns->ns);
> + if (err)
> + goto fail_free;
> +
> + ns->ucounts = ucounts;
> + ns->ns.ops = &timens_operations;
> + ns->user_ns = get_user_ns(user_ns);
> + return ns;
> +
> +fail_free:
> + kfree(ns);
> +fail_dec:
> + dec_time_namespaces(ucounts);
> +fail:
> + return ERR_PTR(err);
> +}
> +
> +/*
> + * Add a reference to old_ns, or clone it if @flags specify CLONE_NEWTIME.
> + * In latter case, changes to the time of this process won't be seen by parent,
> + * and vice versa.
Ditto
> + */
> +struct time_namespace *copy_time_ns(unsigned long flags,
> + struct user_namespace *user_ns, struct time_namespace *old_ns)
> +{
> + if (!(flags & CLONE_NEWTIME))
> + return get_time_ns(old_ns);
> +
> + return clone_time_ns(user_ns, old_ns);
> +}
> +
> +void free_time_ns(struct kref *kref)
> +{
> + struct time_namespace *ns;
> +
> + ns = container_of(kref, struct time_namespace, kref);
> + dec_time_namespaces(ns->ucounts);
> + put_user_ns(ns->user_ns);
> + ns_free_inum(&ns->ns);
> + kfree(ns);
> +}
> +
> +static struct time_namespace *to_time_ns(struct ns_common *ns)
> +{
> + return container_of(ns, struct time_namespace, ns);
> +}
> +
> +static struct ns_common *timens_get(struct task_struct *task)
> +{
> + struct time_namespace *ns = NULL;
> + struct nsproxy *nsproxy;
> +
> + task_lock(task);
> + nsproxy = task->nsproxy;
> + if (nsproxy) {
> + ns = nsproxy->time_ns;
> + get_time_ns(ns);
> + }
> + task_unlock(task);
> +
> + return ns ? &ns->ns : NULL;
> +}
> +
> +static struct ns_common *timens_for_children_get(struct task_struct *task)
> +{
> + struct time_namespace *ns = NULL;
> + struct nsproxy *nsproxy;
> +
> + task_lock(task);
> + nsproxy = task->nsproxy;
> + if (nsproxy) {
> + ns = nsproxy->time_ns_for_children;
> + get_time_ns(ns);
> + }
> + task_unlock(task);
> +
> + return ns ? &ns->ns : NULL;
> +}
> +
> +static void timens_put(struct ns_common *ns)
> +{
> + put_time_ns(to_time_ns(ns));
> +}
> +
> +static int timens_install(struct nsproxy *nsproxy, struct ns_common *new)
> +{
> + struct time_namespace *ns = to_time_ns(new);
> +
> + if (!current_is_single_threaded())
> + return -EUSERS;
> +
> + if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
> + !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + get_time_ns(ns);
> + get_time_ns(ns);
Why is this a double get?
> + put_time_ns(nsproxy->time_ns);
> + put_time_ns(nsproxy->time_ns_for_children);
> + nsproxy->time_ns = ns;
> + nsproxy->time_ns_for_children = ns;
> + ns->initialized = true;
> + return 0;
> +}
> +
> +int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk)
> +{
> + struct ns_common *nsc = &nsproxy->time_ns_for_children->ns;
> + struct time_namespace *ns = to_time_ns(nsc);
> +
> + if (nsproxy->time_ns == nsproxy->time_ns_for_children)
> + return 0;
> +
> + get_time_ns(ns);
> + put_time_ns(nsproxy->time_ns);
> + nsproxy->time_ns = ns;
> + ns->initialized = true;
Isn't that one initialized already?
> +
> + return 0;
> +}
> +
> +static struct user_namespace *timens_owner(struct ns_common *ns)
> +{
> + return to_time_ns(ns)->user_ns;
> +}
> +
> +const struct proc_ns_operations timens_operations = {
> + .name = "time",
> + .type = CLONE_NEWTIME,
> + .get = timens_get,
> + .put = timens_put,
> + .install = timens_install,
> + .owner = timens_owner,
> +};
> +
> +const struct proc_ns_operations timens_for_children_operations = {
> + .name = "time_for_children",
> + .type = CLONE_NEWTIME,
> + .get = timens_for_children_get,
> + .put = timens_put,
> + .install = timens_install,
> + .owner = timens_owner,
> +};
> +
> +struct time_namespace init_time_ns = {
> + .kref = KREF_INIT(3),
> + .user_ns = &init_user_ns,
> + .ns.inum = PROC_TIME_INIT_INO,
> + .ns.ops = &timens_operations,
> +};
Inconsisten formatting. The above static initializers are nicely
tabular. This on not.
Thanks,
tglx
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