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![Kirill Tkhai](/assets/img/avatar_default.png)
Switch over uts namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/159644978167.604812.1773586504374412107.stgit@localhost.localdomain Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
177 lines
3.8 KiB
C
177 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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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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#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/cred.h>
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#include <linux/user_namespace.h>
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#include <linux/proc_ns.h>
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#include <linux/sched/task.h>
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static struct kmem_cache *uts_ns_cache __ro_after_init;
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static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
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{
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return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
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}
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static void dec_uts_namespaces(struct ucounts *ucounts)
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{
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dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
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}
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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 = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
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if (uts_ns)
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refcount_set(&uts_ns->ns.count, 1);
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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 ERR_PTR(-ENOMEM) on error (failure to allocate), 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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struct ucounts *ucounts;
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int err;
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err = -ENOSPC;
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ucounts = inc_uts_namespaces(user_ns);
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if (!ucounts)
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goto fail;
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err = -ENOMEM;
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ns = create_uts_ns();
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if (!ns)
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goto fail_dec;
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err = ns_alloc_inum(&ns->ns);
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if (err)
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goto fail_free;
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ns->ucounts = ucounts;
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ns->ns.ops = &utsns_operations;
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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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fail_free:
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kmem_cache_free(uts_ns_cache, ns);
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fail_dec:
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dec_uts_namespaces(ucounts);
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fail:
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return ERR_PTR(err);
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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 uts_namespace *ns)
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{
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dec_uts_namespaces(ns->ucounts);
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put_user_ns(ns->user_ns);
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ns_free_inum(&ns->ns);
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kmem_cache_free(uts_ns_cache, ns);
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}
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static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
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{
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return container_of(ns, struct uts_namespace, ns);
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}
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static struct ns_common *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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task_lock(task);
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nsproxy = task->nsproxy;
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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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task_unlock(task);
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return ns ? &ns->ns : NULL;
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}
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static void utsns_put(struct ns_common *ns)
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{
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put_uts_ns(to_uts_ns(ns));
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}
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static int utsns_install(struct nsset *nsset, struct ns_common *new)
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{
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struct nsproxy *nsproxy = nsset->nsproxy;
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struct uts_namespace *ns = to_uts_ns(new);
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if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
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!ns_capable(nsset->cred->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 struct user_namespace *utsns_owner(struct ns_common *ns)
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{
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return to_uts_ns(ns)->user_ns;
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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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.owner = utsns_owner,
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};
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void __init uts_ns_init(void)
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{
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uts_ns_cache = kmem_cache_create_usercopy(
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"uts_namespace", sizeof(struct uts_namespace), 0,
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SLAB_PANIC|SLAB_ACCOUNT,
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offsetof(struct uts_namespace, name),
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sizeof_field(struct uts_namespace, name),
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NULL);
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}
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