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Date: Wed, 05 Nov 2014 13:11:06 +0100
From: Richard Weinberger <richard@....at>
To: Chen Hanxiao <chenhanxiao@...fujitsu.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Serge Hallyn <serge.hallyn@...ntu.com>,
Oleg Nesterov <oleg@...hat.com>
CC: containers@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
Pavel Emelyanov <xemul@...allels.com>,
Vasiliy Kulikov <segooon@...il.com>,
Mateusz Guzik <mguzik@...hat.com>
Subject: Re: [PATCH 1/2v6] procfs: show hierarchy of pid namespace
Am 05.11.2014 um 11:41 schrieb Chen Hanxiao:
> We lack of pid hierarchy information, and this will lead to:
> a) we don't know pids' relationship, who is whose child:
> /proc/PID/ns/pid only tell us whether two pids live in different ns
> b) bring trouble to nested lxc container check/restore/migration
> c) bring trouble to pid translation between containers;
>
> This patch will show the hierarchy of pid namespace
> by pidns_hierarchy like:
>
> [root@...alhost ~]#cat /proc/pidns_hierarchy
> 18060 18102 1534
> 18060 18102 1600
> 1550
Hmm, what about printing the pid hierarchy in the same way as /proc/self/mountinfo
does with mount namespaces?
Your current approach is not bad but we should really try to be consistent with existing
sources of information.
> *Note: numbers represent the pid 1 in different ns
>
> It shows the pid hierarchy below:
>
> init_pid_ns (not showed in /proc/pidns_hierarchy)
> │
> ┌────────────┐
> ns1 ns2
> │ │
> 1550 18060
> │
> │
> ns3
> │
> 18102
> │
> ┌──────────┐
> ns4 ns5
> │ │
> 1534 1600
>
> Every pid printed in pidns_hierarchy
> is the init pid of that pid ns level.
>
> Signed-off-by: Chen Hanxiao <chenhanxiao@...fujitsu.com>
> ---
> v6: fix get_pid leaks and do some cleanups;
> v5: collect pid by find_ge_pid;
> use local list inside nslist_proc_show;
> use get_pid, remove mutex lock.
> v4: simplify pid collection and some performance optimizamtion
> fix another race issue.
> v3: fix a race issue and memory leak issue
> v2: use a procfs text file instead of dirs under /proc
>
> fs/proc/Kconfig | 6 ++
> fs/proc/Makefile | 1 +
> fs/proc/pidns_hierarchy.c | 227 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 234 insertions(+)
> create mode 100644 fs/proc/pidns_hierarchy.c
>
> diff --git a/fs/proc/Kconfig b/fs/proc/Kconfig
> index 2183fcf..4bb111c 100644
> --- a/fs/proc/Kconfig
> +++ b/fs/proc/Kconfig
> @@ -71,3 +71,9 @@ config PROC_PAGE_MONITOR
> /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap,
> /proc/kpagecount, and /proc/kpageflags. Disabling these
> interfaces will reduce the size of the kernel by approximately 4kb.
> +
> +config PROC_PID_HIERARCHY
> + bool "Enable /proc/pidns_hierarchy support" if EXPERT
> + depends on PROC_FS
> + help
> + Show pid namespace hierarchy information
Why does this depend on EXPERT?
Every Linux distro will enable this option.
> diff --git a/fs/proc/Makefile b/fs/proc/Makefile
> index 7151ea4..33e384b 100644
> --- a/fs/proc/Makefile
> +++ b/fs/proc/Makefile
> @@ -30,3 +30,4 @@ proc-$(CONFIG_PROC_KCORE) += kcore.o
> proc-$(CONFIG_PROC_VMCORE) += vmcore.o
> proc-$(CONFIG_PRINTK) += kmsg.o
> proc-$(CONFIG_PROC_PAGE_MONITOR) += page.o
> +proc-$(CONFIG_PROC_PID_HIERARCHY) += pidns_hierarchy.o
> diff --git a/fs/proc/pidns_hierarchy.c b/fs/proc/pidns_hierarchy.c
> new file mode 100644
> index 0000000..aee359f
> --- /dev/null
> +++ b/fs/proc/pidns_hierarchy.c
> @@ -0,0 +1,227 @@
> +#include <linux/init.h>
> +#include <linux/errno.h>
> +#include <linux/proc_fs.h>
> +#include <linux/module.h>
> +#include <linux/list.h>
> +#include <linux/slab.h>
> +#include <linux/pid_namespace.h>
> +#include <linux/seq_file.h>
> +
> +/*
> + * /proc/pidns_hierarchy
> + *
> + * show the hierarchy of pid namespace
> + */
> +
> +#define NS_HIERARCHY "pidns_hierarchy"
> +
> +/* list for host pid collection */
> +struct pidns_list {
> + struct list_head list;
> + struct pid *pid;
> +};
> +
> +static void free_pidns_list(struct list_head *head)
> +{
> + struct pidns_list *tmp, *pos;
> +
> + list_for_each_entry_safe(pos, tmp, head, list) {
> + list_del(&pos->list);
> + put_pid(pos->pid);
> + kfree(pos);
> + }
> +}
> +
> +static int
> +pidns_list_add(struct pid *pid, struct list_head *list_head)
> +{
> + struct pidns_list *ent;
> +
> + ent = kmalloc(sizeof(*ent), GFP_KERNEL);
> + if (!ent)
> + return -ENOMEM;
> +
> + ent->pid = pid;
> + list_add_tail(&ent->list, list_head);
> +
> + return 0;
> +}
> +
> +static int
> +pidns_list_filter(struct list_head *pidns_pid_list,
> + struct list_head *pidns_pid_tree)
> +{
> + struct pidns_list *pos, *pos_t;
> + struct pid_namespace *ns0, *ns1;
> + struct pid *pid0, *pid1;
> + int rc, flag = 0;
> +
> + /*
> + * screen pids with relationship
> + * in pidns_pid_list, we may add pids like:
> + * ns0 ns1 ns2
> + * pid1->pid2->pid3
> + * we should screen pid1, pid2 and keep pid3
> + */
> + list_for_each_entry(pos, pidns_pid_list, list) {
> + list_for_each_entry(pos_t, pidns_pid_list, list) {
> + flag = 0;
> + pid0 = pos->pid;
> + pid1 = pos_t->pid;
> + ns0 = pid0->numbers[pid0->level].ns;
> + ns1 = pid1->numbers[pid1->level].ns;
> + if (pos->pid->level < pos_t->pid->level)
> + for (; ns1 != NULL; ns1 = ns1->parent)
> + if (ns0 == ns1) {
> + flag = 1;
> + break;
> + }
> + /* a redundant pid found */
> + if (flag == 1)
> + break;
> + }
> +
> + if (flag == 0) {
> + rcu_read_lock();
> + get_pid(pos->pid);
> + rcu_read_unlock();
> + rc = pidns_list_add(pos->pid, pidns_pid_tree);
> + if (rc) {
> + put_pid(pos->pid);
> + goto out;
> + }
> + }
> + }
> +
> + /*
> + * Now all usefull stuffs are in pidns_pid_tree,
> + * free pidns_pid_list
> + */
> + free_pidns_list(pidns_pid_list);
> +
> + return 0;
> +
> +out:
> + free_pidns_list(pidns_pid_tree);
> + return rc;
> +}
> +
> +/*
> + * collect pids and stored in pidns_pid_list,
> + * then remove duplicated ones,
> + * add the rest to pidns_pid_tree
> + */
> +static int proc_pidns_list_refresh(struct pid_namespace *curr_ns,
> + struct list_head *pidns_pid_list,
> + struct list_head *pidns_pid_tree)
> +{
> + struct pid *pid;
> + int new_nr, nr = 0;
> + int rc;
> +
> + /* collect pids in current namespace */
> + while (nr < PID_MAX_LIMIT) {
> + rcu_read_lock();
> + pid = find_ge_pid(nr, curr_ns);
> + if (pid) {
> + new_nr = pid_vnr(pid);
> + if (!is_child_reaper(pid)) {
> + nr = new_nr + 1;
> + rcu_read_unlock();
> + continue;
> + }
> + get_pid(pid);
> + rcu_read_unlock();
> + rc = pidns_list_add(pid, pidns_pid_list);
This function allocates memory per PID. If we have lots of PIDs, how does this scale?
I'd go so far and say this can be a DoS'able issue if the pidns_hierarchy file is opened multiple times...
Thanks,
//richard
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