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pidns: Make the pidns proc mount/umount logic obvious.
Track the number of pids in the proc hash table. When the number of pids goes to 0 schedule work to unmount the kernel mount of proc. Move the mount of proc into alloc_pid when we allocate the pid for init. Remove the surprising calls of pid_ns_release proc in fork and proc_flush_task. Those code paths really shouldn't know about proc namespace implementation details and people have demonstrated several times that finding and understanding those code paths is difficult and non-obvious. Because of the call path detach pid is alwasy called with the rtnl_lock held free_pid is not allowed to sleep, so the work to unmounting proc is moved to a work queue. This has the side benefit of not blocking the entire world waiting for the unnecessary rcu_barrier in deactivate_locked_super. In the process of making the code clear and obvious this fixes a bug reported by Gao feng <gaofeng@cn.fujitsu.com> where we would leak a mount of proc during clone(CLONE_NEWPID|CLONE_NEWNET) if copy_pid_ns succeeded and copy_net_ns failed. Acked-by: "Serge E. Hallyn" <serge@hallyn.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
parent
17cf22c33e
commit
0a01f2cc39
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@ -2590,10 +2590,6 @@ void proc_flush_task(struct task_struct *task)
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proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
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tgid->numbers[i].nr);
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}
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upid = &pid->numbers[pid->level];
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if (upid->nr == 1)
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pid_ns_release_proc(upid->ns);
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}
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static struct dentry *proc_pid_instantiate(struct inode *dir,
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@ -155,11 +155,6 @@ void __init proc_root_init(void)
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err = register_filesystem(&proc_fs_type);
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if (err)
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return;
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err = pid_ns_prepare_proc(&init_pid_ns);
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if (err) {
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unregister_filesystem(&proc_fs_type);
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return;
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}
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proc_self_init();
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proc_symlink("mounts", NULL, "self/mounts");
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@ -21,6 +21,7 @@ struct pid_namespace {
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struct kref kref;
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struct pidmap pidmap[PIDMAP_ENTRIES];
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int last_pid;
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int nr_hashed;
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struct task_struct *child_reaper;
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struct kmem_cache *pid_cachep;
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unsigned int level;
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@ -32,6 +33,7 @@ struct pid_namespace {
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struct bsd_acct_struct *bacct;
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#endif
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struct user_namespace *user_ns;
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struct work_struct proc_work;
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kgid_t pid_gid;
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int hide_pid;
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int reboot; /* group exit code if this pidns was rebooted */
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@ -1476,8 +1476,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
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if (p->io_context)
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exit_io_context(p);
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bad_fork_cleanup_namespaces:
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if (unlikely(clone_flags & CLONE_NEWPID))
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pid_ns_release_proc(p->nsproxy->pid_ns);
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exit_task_namespaces(p);
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bad_fork_cleanup_mm:
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if (p->mm)
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21
kernel/pid.c
21
kernel/pid.c
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@ -36,6 +36,7 @@
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#include <linux/pid_namespace.h>
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#include <linux/init_task.h>
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#include <linux/syscalls.h>
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#include <linux/proc_fs.h>
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#define pid_hashfn(nr, ns) \
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hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
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@ -270,8 +271,12 @@ void free_pid(struct pid *pid)
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unsigned long flags;
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spin_lock_irqsave(&pidmap_lock, flags);
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for (i = 0; i <= pid->level; i++)
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hlist_del_rcu(&pid->numbers[i].pid_chain);
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for (i = 0; i <= pid->level; i++) {
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struct upid *upid = pid->numbers + i;
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hlist_del_rcu(&upid->pid_chain);
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if (--upid->ns->nr_hashed == 0)
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schedule_work(&upid->ns->proc_work);
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}
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spin_unlock_irqrestore(&pidmap_lock, flags);
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for (i = 0; i <= pid->level; i++)
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@ -293,6 +298,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
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goto out;
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tmp = ns;
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pid->level = ns->level;
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for (i = ns->level; i >= 0; i--) {
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nr = alloc_pidmap(tmp);
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if (nr < 0)
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@ -303,17 +309,23 @@ struct pid *alloc_pid(struct pid_namespace *ns)
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tmp = tmp->parent;
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}
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if (unlikely(is_child_reaper(pid))) {
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if (pid_ns_prepare_proc(ns))
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goto out_free;
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}
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get_pid_ns(ns);
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pid->level = ns->level;
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atomic_set(&pid->count, 1);
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for (type = 0; type < PIDTYPE_MAX; ++type)
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INIT_HLIST_HEAD(&pid->tasks[type]);
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upid = pid->numbers + ns->level;
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spin_lock_irq(&pidmap_lock);
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for ( ; upid >= pid->numbers; --upid)
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for ( ; upid >= pid->numbers; --upid) {
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hlist_add_head_rcu(&upid->pid_chain,
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&pid_hash[pid_hashfn(upid->nr, upid->ns)]);
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upid->ns->nr_hashed++;
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}
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spin_unlock_irq(&pidmap_lock);
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out:
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@ -570,6 +582,7 @@ void __init pidmap_init(void)
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/* Reserve PID 0. We never call free_pidmap(0) */
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set_bit(0, init_pid_ns.pidmap[0].page);
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atomic_dec(&init_pid_ns.pidmap[0].nr_free);
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init_pid_ns.nr_hashed = 1;
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init_pid_ns.pid_cachep = KMEM_CACHE(pid,
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SLAB_HWCACHE_ALIGN | SLAB_PANIC);
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@ -72,6 +72,12 @@ static struct kmem_cache *create_pid_cachep(int nr_ids)
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return NULL;
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}
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static void proc_cleanup_work(struct work_struct *work)
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{
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struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
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pid_ns_release_proc(ns);
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}
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/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
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#define MAX_PID_NS_LEVEL 32
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@ -105,6 +111,7 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
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ns->level = level;
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ns->parent = get_pid_ns(parent_pid_ns);
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ns->user_ns = get_user_ns(user_ns);
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INIT_WORK(&ns->proc_work, proc_cleanup_work);
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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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@ -112,15 +119,8 @@ static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns
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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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err = pid_ns_prepare_proc(ns);
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if (err)
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goto out_put_parent_pid_ns;
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return ns;
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out_put_parent_pid_ns:
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put_pid_ns(parent_pid_ns);
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put_user_ns(user_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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