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![Oleg Nesterov](/assets/img/avatar_default.png)
We don't change pid_ns->child_reaper when the main thread of the subnamespace init exits. As Robert Rex <robert.rex@exasol.com> pointed out this is wrong. Yes, the re-parenting itself works correctly, but if the reparented task exits it needs ->parent->nsproxy->pid_ns in do_notify_parent(), and if the main thread is zombie its ->nsproxy was already cleared by exit_task_namespaces(). Introduce the new function, find_new_reaper(), which finds the new ->parent for the re-parenting and changes ->child_reaper if needed. Kill the now unneeded exit_child_reaper(). Also move the changing of ->child_reaper from zap_pid_ns_processes() to find_new_reaper(), this consolidates the games with ->child_reaper and makes it stable under tasklist_lock. Addresses http://bugzilla.kernel.org/show_bug.cgi?id=11391 Reported-by: Robert Rex <robert.rex@exasol.com> Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Pavel Emelyanov <xemul@openvz.org> Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
192 lines
4.2 KiB
C
192 lines
4.2 KiB
C
/*
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* Pid namespaces
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*
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* Authors:
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* (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
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* (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
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* Many thanks to Oleg Nesterov for comments and help
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*
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*/
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#include <linux/pid.h>
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#include <linux/pid_namespace.h>
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#include <linux/syscalls.h>
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#include <linux/err.h>
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#include <linux/acct.h>
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#define BITS_PER_PAGE (PAGE_SIZE*8)
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struct pid_cache {
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int nr_ids;
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char name[16];
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struct kmem_cache *cachep;
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struct list_head list;
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};
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static LIST_HEAD(pid_caches_lh);
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static DEFINE_MUTEX(pid_caches_mutex);
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static struct kmem_cache *pid_ns_cachep;
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/*
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* creates the kmem cache to allocate pids from.
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* @nr_ids: the number of numerical ids this pid will have to carry
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*/
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static struct kmem_cache *create_pid_cachep(int nr_ids)
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{
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struct pid_cache *pcache;
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struct kmem_cache *cachep;
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mutex_lock(&pid_caches_mutex);
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list_for_each_entry(pcache, &pid_caches_lh, list)
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if (pcache->nr_ids == nr_ids)
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goto out;
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pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
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if (pcache == NULL)
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goto err_alloc;
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snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
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cachep = kmem_cache_create(pcache->name,
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sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
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0, SLAB_HWCACHE_ALIGN, NULL);
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if (cachep == NULL)
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goto err_cachep;
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pcache->nr_ids = nr_ids;
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pcache->cachep = cachep;
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list_add(&pcache->list, &pid_caches_lh);
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out:
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mutex_unlock(&pid_caches_mutex);
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return pcache->cachep;
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err_cachep:
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kfree(pcache);
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err_alloc:
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mutex_unlock(&pid_caches_mutex);
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return NULL;
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}
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static struct pid_namespace *create_pid_namespace(unsigned int level)
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{
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struct pid_namespace *ns;
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int i;
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ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
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if (ns == NULL)
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goto out;
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ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
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if (!ns->pidmap[0].page)
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goto out_free;
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ns->pid_cachep = create_pid_cachep(level + 1);
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if (ns->pid_cachep == NULL)
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goto out_free_map;
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kref_init(&ns->kref);
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ns->level = level;
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set_bit(0, ns->pidmap[0].page);
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atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
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for (i = 1; i < PIDMAP_ENTRIES; i++)
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atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
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return ns;
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out_free_map:
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kfree(ns->pidmap[0].page);
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out_free:
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kmem_cache_free(pid_ns_cachep, ns);
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out:
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return ERR_PTR(-ENOMEM);
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}
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static void destroy_pid_namespace(struct pid_namespace *ns)
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{
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int i;
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for (i = 0; i < PIDMAP_ENTRIES; i++)
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kfree(ns->pidmap[i].page);
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kmem_cache_free(pid_ns_cachep, ns);
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}
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struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
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{
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struct pid_namespace *new_ns;
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BUG_ON(!old_ns);
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new_ns = get_pid_ns(old_ns);
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if (!(flags & CLONE_NEWPID))
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goto out;
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new_ns = ERR_PTR(-EINVAL);
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if (flags & CLONE_THREAD)
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goto out_put;
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new_ns = create_pid_namespace(old_ns->level + 1);
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if (!IS_ERR(new_ns))
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new_ns->parent = get_pid_ns(old_ns);
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out_put:
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put_pid_ns(old_ns);
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out:
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return new_ns;
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}
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void free_pid_ns(struct kref *kref)
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{
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struct pid_namespace *ns, *parent;
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ns = container_of(kref, struct pid_namespace, kref);
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parent = ns->parent;
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destroy_pid_namespace(ns);
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if (parent != NULL)
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put_pid_ns(parent);
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}
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void zap_pid_ns_processes(struct pid_namespace *pid_ns)
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{
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int nr;
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int rc;
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/*
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* The last thread in the cgroup-init thread group is terminating.
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* Find remaining pid_ts in the namespace, signal and wait for them
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* to exit.
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*
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* Note: This signals each threads in the namespace - even those that
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* belong to the same thread group, To avoid this, we would have
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* to walk the entire tasklist looking a processes in this
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* namespace, but that could be unnecessarily expensive if the
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* pid namespace has just a few processes. Or we need to
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* maintain a tasklist for each pid namespace.
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*
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*/
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read_lock(&tasklist_lock);
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nr = next_pidmap(pid_ns, 1);
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while (nr > 0) {
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kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
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nr = next_pidmap(pid_ns, nr);
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}
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read_unlock(&tasklist_lock);
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do {
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clear_thread_flag(TIF_SIGPENDING);
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rc = sys_wait4(-1, NULL, __WALL, NULL);
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} while (rc != -ECHILD);
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acct_exit_ns(pid_ns);
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return;
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}
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static __init int pid_namespaces_init(void)
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{
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pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
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return 0;
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}
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__initcall(pid_namespaces_init);
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