98f842e675
Assign a unique proc inode to each namespace, and use that inode number to ensure we only allocate at most one proc inode for every namespace in proc. A single proc inode per namespace allows userspace to test to see if two processes are in the same namespace. This has been a long requested feature and only blocked because a naive implementation would put the id in a global space and would ultimately require having a namespace for the names of namespaces, making migration and certain virtualization tricks impossible. We still don't have per superblock inode numbers for proc, which appears necessary for application unaware checkpoint/restart and migrations (if the application is using namespace file descriptors) but that is now allowd by the design if it becomes important. I have preallocated the ipc and uts initial proc inode numbers so their structures can be statically initialized. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
140 lines
2.8 KiB
C
140 lines
2.8 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 user_namespace *user_ns,
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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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int err;
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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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err = proc_alloc_inum(&ns->proc_inum);
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if (err) {
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kfree(ns);
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return ERR_PTR(err);
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}
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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(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 user_namespace *user_ns, struct uts_namespace *old_ns)
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{
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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(user_ns, 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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proc_free_inum(ns->proc_inum);
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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 *new)
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{
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struct uts_namespace *ns = new;
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if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
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return -EPERM;
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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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static unsigned int utsns_inum(void *vp)
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{
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struct uts_namespace *ns = vp;
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return ns->proc_inum;
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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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.inum = utsns_inum,
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};
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