mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-28 20:02:17 +00:00
![Christian Brauner](/assets/img/avatar_default.png)
Add a simple struct nsset. It holds all necessary pieces to switch to a new set of namespaces without leaving a task in a half-switched state which we will make use of in the next patch. This patch switches the existing setns logic over without causing a change in setns() behavior. This brings setns() closer to how unshare() works(). The prepare_ns() function is responsible to prepare all necessary information. This has two reasons. First it minimizes dependencies between individual namespaces, i.e. all install handler can expect that all fields are properly initialized independent in what order they are called in. Second, this makes the code easier to maintain and easier to follow if it needs to be changed. The prepare_ns() helper will only be switched over to use a flags argument in the next patch. Here it will still use nstype as a simple integer argument which was argued would be clearer. I'm not particularly opinionated about this if it really helps or not. The struct nsset itself already contains the flags field since its name already indicates that it can contain information required by different namespaces. None of this should have functional consequences. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Serge Hallyn <serge@hallyn.com> Cc: Jann Horn <jannh@google.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
180 lines
3.8 KiB
C
180 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Copyright (C) 2004 IBM Corporation
|
|
*
|
|
* Author: Serge Hallyn <serue@us.ibm.com>
|
|
*/
|
|
|
|
#include <linux/export.h>
|
|
#include <linux/uts.h>
|
|
#include <linux/utsname.h>
|
|
#include <linux/err.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/cred.h>
|
|
#include <linux/user_namespace.h>
|
|
#include <linux/proc_ns.h>
|
|
#include <linux/sched/task.h>
|
|
|
|
static struct kmem_cache *uts_ns_cache __ro_after_init;
|
|
|
|
static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
|
|
{
|
|
return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
|
|
}
|
|
|
|
static void dec_uts_namespaces(struct ucounts *ucounts)
|
|
{
|
|
dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
|
|
}
|
|
|
|
static struct uts_namespace *create_uts_ns(void)
|
|
{
|
|
struct uts_namespace *uts_ns;
|
|
|
|
uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
|
|
if (uts_ns)
|
|
kref_init(&uts_ns->kref);
|
|
return uts_ns;
|
|
}
|
|
|
|
/*
|
|
* Clone a new ns copying an original utsname, setting refcount to 1
|
|
* @old_ns: namespace to clone
|
|
* Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
|
|
*/
|
|
static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
|
|
struct uts_namespace *old_ns)
|
|
{
|
|
struct uts_namespace *ns;
|
|
struct ucounts *ucounts;
|
|
int err;
|
|
|
|
err = -ENOSPC;
|
|
ucounts = inc_uts_namespaces(user_ns);
|
|
if (!ucounts)
|
|
goto fail;
|
|
|
|
err = -ENOMEM;
|
|
ns = create_uts_ns();
|
|
if (!ns)
|
|
goto fail_dec;
|
|
|
|
err = ns_alloc_inum(&ns->ns);
|
|
if (err)
|
|
goto fail_free;
|
|
|
|
ns->ucounts = ucounts;
|
|
ns->ns.ops = &utsns_operations;
|
|
|
|
down_read(&uts_sem);
|
|
memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
|
|
ns->user_ns = get_user_ns(user_ns);
|
|
up_read(&uts_sem);
|
|
return ns;
|
|
|
|
fail_free:
|
|
kmem_cache_free(uts_ns_cache, ns);
|
|
fail_dec:
|
|
dec_uts_namespaces(ucounts);
|
|
fail:
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
/*
|
|
* Copy task tsk's utsname namespace, or clone it if flags
|
|
* specifies CLONE_NEWUTS. In latter case, changes to the
|
|
* utsname of this process won't be seen by parent, and vice
|
|
* versa.
|
|
*/
|
|
struct uts_namespace *copy_utsname(unsigned long flags,
|
|
struct user_namespace *user_ns, struct uts_namespace *old_ns)
|
|
{
|
|
struct uts_namespace *new_ns;
|
|
|
|
BUG_ON(!old_ns);
|
|
get_uts_ns(old_ns);
|
|
|
|
if (!(flags & CLONE_NEWUTS))
|
|
return old_ns;
|
|
|
|
new_ns = clone_uts_ns(user_ns, old_ns);
|
|
|
|
put_uts_ns(old_ns);
|
|
return new_ns;
|
|
}
|
|
|
|
void free_uts_ns(struct kref *kref)
|
|
{
|
|
struct uts_namespace *ns;
|
|
|
|
ns = container_of(kref, struct uts_namespace, kref);
|
|
dec_uts_namespaces(ns->ucounts);
|
|
put_user_ns(ns->user_ns);
|
|
ns_free_inum(&ns->ns);
|
|
kmem_cache_free(uts_ns_cache, ns);
|
|
}
|
|
|
|
static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
|
|
{
|
|
return container_of(ns, struct uts_namespace, ns);
|
|
}
|
|
|
|
static struct ns_common *utsns_get(struct task_struct *task)
|
|
{
|
|
struct uts_namespace *ns = NULL;
|
|
struct nsproxy *nsproxy;
|
|
|
|
task_lock(task);
|
|
nsproxy = task->nsproxy;
|
|
if (nsproxy) {
|
|
ns = nsproxy->uts_ns;
|
|
get_uts_ns(ns);
|
|
}
|
|
task_unlock(task);
|
|
|
|
return ns ? &ns->ns : NULL;
|
|
}
|
|
|
|
static void utsns_put(struct ns_common *ns)
|
|
{
|
|
put_uts_ns(to_uts_ns(ns));
|
|
}
|
|
|
|
static int utsns_install(struct nsset *nsset, struct ns_common *new)
|
|
{
|
|
struct nsproxy *nsproxy = nsset->nsproxy;
|
|
struct uts_namespace *ns = to_uts_ns(new);
|
|
|
|
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
|
|
!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
|
|
get_uts_ns(ns);
|
|
put_uts_ns(nsproxy->uts_ns);
|
|
nsproxy->uts_ns = ns;
|
|
return 0;
|
|
}
|
|
|
|
static struct user_namespace *utsns_owner(struct ns_common *ns)
|
|
{
|
|
return to_uts_ns(ns)->user_ns;
|
|
}
|
|
|
|
const struct proc_ns_operations utsns_operations = {
|
|
.name = "uts",
|
|
.type = CLONE_NEWUTS,
|
|
.get = utsns_get,
|
|
.put = utsns_put,
|
|
.install = utsns_install,
|
|
.owner = utsns_owner,
|
|
};
|
|
|
|
void __init uts_ns_init(void)
|
|
{
|
|
uts_ns_cache = kmem_cache_create_usercopy(
|
|
"uts_namespace", sizeof(struct uts_namespace), 0,
|
|
SLAB_PANIC|SLAB_ACCOUNT,
|
|
offsetof(struct uts_namespace, name),
|
|
sizeof_field(struct uts_namespace, name),
|
|
NULL);
|
|
}
|