c4a4d60379
Optimize performance and prepare for the removal of the user_ns reference from user_struct. Remove the slow long walk through cred->user->user_ns and instead go straight to cred->user_ns. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
120 lines
2.5 KiB
C
120 lines
2.5 KiB
C
/*
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* Copyright (C) 2004 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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#include <linux/export.h>
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#include <linux/uts.h>
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#include <linux/utsname.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/user_namespace.h>
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#include <linux/proc_fs.h>
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static struct uts_namespace *create_uts_ns(void)
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{
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struct uts_namespace *uts_ns;
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uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
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if (uts_ns)
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kref_init(&uts_ns->kref);
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return uts_ns;
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}
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/*
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* Clone a new ns copying an original utsname, setting refcount to 1
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* @old_ns: namespace to clone
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* Return NULL on error (failure to kmalloc), new ns otherwise
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*/
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static struct uts_namespace *clone_uts_ns(struct task_struct *tsk,
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struct uts_namespace *old_ns)
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{
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struct uts_namespace *ns;
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ns = create_uts_ns();
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if (!ns)
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return ERR_PTR(-ENOMEM);
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down_read(&uts_sem);
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memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
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ns->user_ns = get_user_ns(task_cred_xxx(tsk, user_ns));
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up_read(&uts_sem);
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return ns;
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}
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/*
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* Copy task tsk's utsname namespace, or clone it if flags
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* specifies CLONE_NEWUTS. In latter case, changes to the
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* utsname of this process won't be seen by parent, and vice
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* versa.
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*/
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struct uts_namespace *copy_utsname(unsigned long flags,
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struct task_struct *tsk)
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{
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struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
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struct uts_namespace *new_ns;
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BUG_ON(!old_ns);
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get_uts_ns(old_ns);
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if (!(flags & CLONE_NEWUTS))
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return old_ns;
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new_ns = clone_uts_ns(tsk, old_ns);
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put_uts_ns(old_ns);
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return new_ns;
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}
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void free_uts_ns(struct kref *kref)
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{
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struct uts_namespace *ns;
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ns = container_of(kref, struct uts_namespace, kref);
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put_user_ns(ns->user_ns);
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kfree(ns);
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}
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static void *utsns_get(struct task_struct *task)
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{
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struct uts_namespace *ns = NULL;
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struct nsproxy *nsproxy;
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rcu_read_lock();
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nsproxy = task_nsproxy(task);
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if (nsproxy) {
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ns = nsproxy->uts_ns;
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get_uts_ns(ns);
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}
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rcu_read_unlock();
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return ns;
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}
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static void utsns_put(void *ns)
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{
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put_uts_ns(ns);
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}
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static int utsns_install(struct nsproxy *nsproxy, void *ns)
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{
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get_uts_ns(ns);
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put_uts_ns(nsproxy->uts_ns);
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nsproxy->uts_ns = ns;
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return 0;
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}
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const struct proc_ns_operations utsns_operations = {
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.name = "uts",
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.type = CLONE_NEWUTS,
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.get = utsns_get,
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.put = utsns_put,
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.install = utsns_install,
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};
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