7a238fcba0
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>
164 lines
3.1 KiB
C
164 lines
3.1 KiB
C
/*
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* Copyright (C) 2006 IBM Corporation
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*
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* Author: Serge Hallyn <serue@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*
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* Jun 2006 - namespaces support
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* OpenVZ, SWsoft Inc.
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* Pavel Emelianov <xemul@openvz.org>
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*/
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#include <linux/module.h>
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#include <linux/version.h>
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#include <linux/nsproxy.h>
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#include <linux/init_task.h>
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#include <linux/mnt_namespace.h>
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#include <linux/utsname.h>
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#include <linux/pid_namespace.h>
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struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
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static inline void get_nsproxy(struct nsproxy *ns)
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{
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atomic_inc(&ns->count);
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}
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void get_task_namespaces(struct task_struct *tsk)
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{
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struct nsproxy *ns = tsk->nsproxy;
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if (ns) {
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get_nsproxy(ns);
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}
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}
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/*
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* creates a copy of "orig" with refcount 1.
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* This does not grab references to the contained namespaces,
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* so that needs to be done by dup_namespaces.
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*/
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static inline struct nsproxy *clone_namespaces(struct nsproxy *orig)
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{
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struct nsproxy *ns;
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ns = kmemdup(orig, sizeof(struct nsproxy), GFP_KERNEL);
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if (ns)
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atomic_set(&ns->count, 1);
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return ns;
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}
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/*
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* copies the nsproxy, setting refcount to 1, and grabbing a
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* reference to all contained namespaces. Called from
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* sys_unshare()
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*/
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struct nsproxy *dup_namespaces(struct nsproxy *orig)
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{
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struct nsproxy *ns = clone_namespaces(orig);
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if (ns) {
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if (ns->mnt_ns)
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get_mnt_ns(ns->mnt_ns);
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if (ns->uts_ns)
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get_uts_ns(ns->uts_ns);
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if (ns->ipc_ns)
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get_ipc_ns(ns->ipc_ns);
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if (ns->pid_ns)
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get_pid_ns(ns->pid_ns);
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}
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return ns;
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}
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/*
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* called from clone. This now handles copy for nsproxy and all
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* namespaces therein.
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*/
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int copy_namespaces(int flags, struct task_struct *tsk)
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{
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struct nsproxy *old_ns = tsk->nsproxy;
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struct nsproxy *new_ns;
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int err = 0;
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if (!old_ns)
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return 0;
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get_nsproxy(old_ns);
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if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC)))
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return 0;
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new_ns = clone_namespaces(old_ns);
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if (!new_ns) {
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err = -ENOMEM;
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goto out;
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}
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tsk->nsproxy = new_ns;
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err = copy_mnt_ns(flags, tsk);
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if (err)
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goto out_ns;
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err = copy_utsname(flags, tsk);
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if (err)
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goto out_uts;
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err = copy_ipcs(flags, tsk);
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if (err)
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goto out_ipc;
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err = copy_pid_ns(flags, tsk);
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if (err)
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goto out_pid;
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out:
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put_and_finalize_nsproxy(old_ns);
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return err;
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out_pid:
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if (new_ns->ipc_ns)
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put_ipc_ns(new_ns->ipc_ns);
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out_ipc:
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if (new_ns->uts_ns)
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put_uts_ns(new_ns->uts_ns);
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out_uts:
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if (new_ns->mnt_ns)
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put_mnt_ns(new_ns->mnt_ns);
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out_ns:
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tsk->nsproxy = old_ns;
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kfree(new_ns);
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goto out;
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}
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struct nsproxy *put_nsproxy(struct nsproxy *ns)
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{
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if (ns) {
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if (atomic_dec_and_test(&ns->count)) {
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if (ns->mnt_ns) {
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put_mnt_ns(ns->mnt_ns);
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ns->mnt_ns = NULL;
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}
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return ns;
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}
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}
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return NULL;
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}
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void free_nsproxy(struct nsproxy *ns)
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{
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if (ns->mnt_ns)
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put_mnt_ns(ns->mnt_ns);
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if (ns->uts_ns)
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put_uts_ns(ns->uts_ns);
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if (ns->ipc_ns)
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put_ipc_ns(ns->ipc_ns);
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if (ns->pid_ns)
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put_pid_ns(ns->pid_ns);
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kfree(ns);
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}
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