linux/kernel/nsproxy.c
Serge E. Hallyn 7a238fcba0 [PATCH] namespaces: fix exit race by splitting exit
Fix exit race by splitting the nsproxy putting into two pieces.  First
piece reduces the nsproxy refcount.  If we dropped the last reference, then
it puts the mnt_ns, and returns the nsproxy as a hint to the caller.  Else
it returns NULL.  The second piece of exiting task namespaces sets
tsk->nsproxy to NULL, and drops the references to other namespaces and
frees the nsproxy only if an nsproxy was passed in.

A little awkward and should probably be reworked, but hopefully it fixes
the NFS oops.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Daniel Hokka Zakrisson <daniel@hozac.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-30 08:26:44 -08:00

164 lines
3.1 KiB
C

/*
* Copyright (C) 2006 IBM Corporation
*
* Author: Serge Hallyn <serue@us.ibm.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*
* Jun 2006 - namespaces support
* OpenVZ, SWsoft Inc.
* Pavel Emelianov <xemul@openvz.org>
*/
#include <linux/module.h>
#include <linux/version.h>
#include <linux/nsproxy.h>
#include <linux/init_task.h>
#include <linux/mnt_namespace.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
static inline void get_nsproxy(struct nsproxy *ns)
{
atomic_inc(&ns->count);
}
void get_task_namespaces(struct task_struct *tsk)
{
struct nsproxy *ns = tsk->nsproxy;
if (ns) {
get_nsproxy(ns);
}
}
/*
* creates a copy of "orig" with refcount 1.
* This does not grab references to the contained namespaces,
* so that needs to be done by dup_namespaces.
*/
static inline struct nsproxy *clone_namespaces(struct nsproxy *orig)
{
struct nsproxy *ns;
ns = kmemdup(orig, sizeof(struct nsproxy), GFP_KERNEL);
if (ns)
atomic_set(&ns->count, 1);
return ns;
}
/*
* copies the nsproxy, setting refcount to 1, and grabbing a
* reference to all contained namespaces. Called from
* sys_unshare()
*/
struct nsproxy *dup_namespaces(struct nsproxy *orig)
{
struct nsproxy *ns = clone_namespaces(orig);
if (ns) {
if (ns->mnt_ns)
get_mnt_ns(ns->mnt_ns);
if (ns->uts_ns)
get_uts_ns(ns->uts_ns);
if (ns->ipc_ns)
get_ipc_ns(ns->ipc_ns);
if (ns->pid_ns)
get_pid_ns(ns->pid_ns);
}
return ns;
}
/*
* called from clone. This now handles copy for nsproxy and all
* namespaces therein.
*/
int copy_namespaces(int flags, struct task_struct *tsk)
{
struct nsproxy *old_ns = tsk->nsproxy;
struct nsproxy *new_ns;
int err = 0;
if (!old_ns)
return 0;
get_nsproxy(old_ns);
if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
return 0;
new_ns = clone_namespaces(old_ns);
if (!new_ns) {
err = -ENOMEM;
goto out;
}
tsk->nsproxy = new_ns;
err = copy_mnt_ns(flags, tsk);
if (err)
goto out_ns;
err = copy_utsname(flags, tsk);
if (err)
goto out_uts;
err = copy_ipcs(flags, tsk);
if (err)
goto out_ipc;
err = copy_pid_ns(flags, tsk);
if (err)
goto out_pid;
out:
put_and_finalize_nsproxy(old_ns);
return err;
out_pid:
if (new_ns->ipc_ns)
put_ipc_ns(new_ns->ipc_ns);
out_ipc:
if (new_ns->uts_ns)
put_uts_ns(new_ns->uts_ns);
out_uts:
if (new_ns->mnt_ns)
put_mnt_ns(new_ns->mnt_ns);
out_ns:
tsk->nsproxy = old_ns;
kfree(new_ns);
goto out;
}
struct nsproxy *put_nsproxy(struct nsproxy *ns)
{
if (ns) {
if (atomic_dec_and_test(&ns->count)) {
if (ns->mnt_ns) {
put_mnt_ns(ns->mnt_ns);
ns->mnt_ns = NULL;
}
return ns;
}
}
return NULL;
}
void free_nsproxy(struct nsproxy *ns)
{
if (ns->mnt_ns)
put_mnt_ns(ns->mnt_ns);
if (ns->uts_ns)
put_uts_ns(ns->uts_ns);
if (ns->ipc_ns)
put_ipc_ns(ns->ipc_ns);
if (ns->pid_ns)
put_pid_ns(ns->pid_ns);
kfree(ns);
}