From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: serge@hallyn.com, ebiederm@xmission.com, agruenba@redhat.com,
linux-api@vger.kernel.org, oleg@redhat.com,
linux-kernel@vger.kernel.org, paul@paul-moore.com,
ktkhai@virtuozzo.com, viro@zeniv.linux.org.uk, avagin@openvz.org,
linux-fsdevel@vger.kernel.org, mtk.manpages@gmail.com,
akpm@linux-foundation.org, luto@amacapital.net,
gorcunov@openvz.org, mingo@kernel.org, keescook@chromium.org
Subject: [PATCH 2/2] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy
Date: Mon, 17 Apr 2017 20:36:17 +0300 [thread overview]
Message-ID: <149245057248.17600.1341652606136269734.stgit@localhost.localdomain> (raw)
In-Reply-To: <149245014695.17600.12640895883798122726.stgit@localhost.localdomain>
On implementing of nested pid namespaces support in CRIU
(checkpoint-restore in userspace tool) we run into
the situation, that it's impossible to create a task with
specific NSpid effectively. After commit 49f4d8b93ccf
"pidns: Capture the user namespace and filter ns_last_pid"
it is impossible to set ns_last_pid on any pid namespace,
except task's active pid_ns (before the commit it was possible
to write to pid_ns_for_children). Thus, if a restored task
in a container has more than one pid_ns levels, the restorer
code must have a task helper for every pid namespace
of the task's pid_ns hierarhy.
This is a big problem, because of communication with
a helper for every pid_ns in the hierarchy is not cheap
and not performance-good as it implies many helpers wakeups
to create a single task (independently, how you communicate
with the helpers). This patch tries to decide the problem.
It introduces a new pid_ns ns_ioctl(PIDNS_REQ_SET_LAST_PID_VEC),
which allows to write a vector of last pids on pid_ns hierarchy.
The vector is passed as a ":"-delimited string with pids,
written in reverse order. The first number corresponds to
the opened namespace ns_last_pid, the second is to its parent, etc.
So, if you have the pid namespaces hierarchy like:
pid_ns1 (grand father)
|
v
pid_ns2 (father)
|
v
pid_ns3 (child)
and the ns of task's of pid_ns3 is open, then the corresponding
vector will be "last_ns_pid3:last_ns_pid2:last_ns_pid1". This
vector may be short and it may contain less levels, for example,
"last_ns_pid3:last_ns_pid2" or even "last_ns_pid3", in dependence
of which levels you want to populate.
To write in a pid_ns's ns_last_pid we check that the writer task
has CAP_SYS_ADMIN permittions in this pid_ns's user_ns.
One note about struct pidns_ioc_req. It's made extensible and
may expanded in the future. The always existing fields present
at the moment, the future fields and they sizes may be determined
by pidns_ioc_req::req by the future code.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
include/uapi/linux/nsfs.h | 9 +++++
kernel/pid_namespace.c | 88 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 97 insertions(+)
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
index 544bbb661475..37bb4af917b5 100644
--- a/include/uapi/linux/nsfs.h
+++ b/include/uapi/linux/nsfs.h
@@ -17,4 +17,13 @@
/* Execute namespace-specific ioctl */
#define NS_SPECIFIC_IOC _IO(NSIO, 0x5)
+struct pidns_ioc_req {
+/* Set vector of last pids in namespace hierarchy */
+#define PIDNS_REQ_SET_LAST_PID_VEC 0x1
+ unsigned int req;
+ void __user *data;
+ unsigned int data_size;
+ char std_fields[0];
+};
+
#endif /* __LINUX_NSFS_H */
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index de461aa0bf9a..0e86fa15cd92 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -21,6 +21,8 @@
#include <linux/export.h>
#include <linux/sched/task.h>
#include <linux/sched/signal.h>
+#include <linux/vmalloc.h>
+#include <uapi/linux/nsfs.h>
struct pid_cache {
int nr_ids;
@@ -428,6 +430,91 @@ static struct ns_common *pidns_get_parent(struct ns_common *ns)
return &get_pid_ns(pid_ns)->ns;
}
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static long set_last_pid_vec(struct pid_namespace *pid_ns,
+ struct pidns_ioc_req *req)
+{
+ char *str, *p;
+ int ret = 0;
+ pid_t pid;
+
+ read_lock(&tasklist_lock);
+ if (!pid_ns->child_reaper)
+ ret = -EINVAL;
+ read_unlock(&tasklist_lock);
+ if (ret)
+ return ret;
+
+ if (req->data_size >= PAGE_SIZE)
+ return -EINVAL;
+ str = vmalloc(req->data_size + 1);
+ if (!str)
+ return -ENOMEM;
+ if (copy_from_user(str, req->data, req->data_size)) {
+ ret = -EFAULT;
+ goto out_vfree;
+ }
+ str[req->data_size] = '\0';
+
+ p = str;
+ while (p && *p != '\0') {
+ if (!ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ goto out_vfree;
+ }
+
+ if (sscanf(p, "%d", &pid) != 1 || pid < 0 || pid > pid_max) {
+ ret = -EINVAL;
+ goto out_vfree;
+ }
+
+ /* Write directly: see the comment in pid_ns_ctl_handler() */
+ pid_ns->last_pid = pid;
+
+ p = strchr(p, ':');
+ pid_ns = pid_ns->parent;
+ if (p) {
+ if (!pid_ns) {
+ ret = -EINVAL;
+ goto out_vfree;
+ }
+ p++;
+ }
+ }
+
+ ret = 0;
+out_vfree:
+ vfree(str);
+ return ret;
+}
+#else /* CONFIG_CHECKPOINT_RESTORE */
+static long set_last_pid_vec(struct pid_namespace *pid_ns,
+ struct pidns_ioc_req *req)
+{
+ return -ENOTTY;
+}
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
+static long pidns_ioctl(struct ns_common *ns, unsigned long arg)
+{
+ struct pid_namespace *pid_ns = to_pid_ns(ns);
+ struct pidns_ioc_req user_req;
+ int ret;
+
+ ret = copy_from_user(&user_req, (void *)arg,
+ offsetof(struct pidns_ioc_req, std_fields));
+ if (ret)
+ return ret;
+
+ switch (user_req.req) {
+ case PIDNS_REQ_SET_LAST_PID_VEC:
+ return set_last_pid_vec(pid_ns, &user_req);
+ default:
+ return -ENOTTY;
+ }
+ return 0;
+}
+
static struct user_namespace *pidns_owner(struct ns_common *ns)
{
return to_pid_ns(ns)->user_ns;
@@ -441,6 +528,7 @@ const struct proc_ns_operations pidns_operations = {
.install = pidns_install,
.owner = pidns_owner,
.get_parent = pidns_get_parent,
+ .ns_ioctl = pidns_ioctl,
};
static __init int pid_namespaces_init(void)
next prev parent reply other threads:[~2017-04-17 17:36 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-17 17:34 [PATCH 0/2] nsfs: Introduce ioctl to set vector of ns_last_pid's on pid ns hierarhy Kirill Tkhai
[not found] ` <149245014695.17600.12640895883798122726.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2017-04-17 17:36 ` [PATCH 1/2] nsfs: Add namespace-specific ioctl (NS_SPECIFIC_IOC) Kirill Tkhai
2017-04-17 17:36 ` Kirill Tkhai [this message]
[not found] ` <149245057248.17600.1341652606136269734.stgit-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2017-04-19 20:27 ` [PATCH 2/2] pid_ns: Introduce ioctl to set vector of ns_last_pid's on ns hierarhy Serge E. Hallyn
2017-04-24 19:03 ` Cyrill Gorcunov
2017-04-26 15:53 ` Oleg Nesterov
[not found] ` <20170426155352.GA12131-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-04-26 16:11 ` Kirill Tkhai
[not found] ` <785e1986-da03-72aa-06c0-234ed2dbc0fd-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-04-26 16:33 ` Kirill Tkhai
[not found] ` <005f52d9-efbe-9eaa-7f36-19945c8b06c3-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-04-26 16:32 ` Eric W. Biederman
[not found] ` <87h91bcep5.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-26 16:43 ` Kirill Tkhai
2017-04-26 17:01 ` Eric W. Biederman
2017-04-27 16:12 ` Oleg Nesterov
2017-04-27 16:17 ` Kirill Tkhai
[not found] ` <fdd61d9c-6f88-1669-4d12-31748395fe99-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-04-27 16:22 ` Oleg Nesterov
2017-04-28 9:17 ` Kirill Tkhai
2017-05-02 16:33 ` Oleg Nesterov
[not found] ` <20170502163324.GA25036-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2017-05-02 17:22 ` Eric W. Biederman
2017-05-02 17:33 ` Kirill Tkhai
[not found] ` <de392430-18b8-d296-b868-82fdedcd0c0e-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
2017-05-02 21:13 ` Eric W. Biederman
[not found] ` <8737cngdxi.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-05-03 10:20 ` Kirill Tkhai
2017-04-27 16:39 ` Eric W. Biederman
[not found] ` <87o9vhztwv.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2017-04-28 9:22 ` Kirill Tkhai
2017-04-27 16:16 ` Oleg Nesterov
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