linux-stable/include/linux/utsname.h
Kirill Tkhai 9a56493f69
uts: Use generic ns_common::count
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>
2020-08-19 14:13:20 +02:00

91 lines
1.8 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_UTSNAME_H
#define _LINUX_UTSNAME_H
#include <linux/sched.h>
#include <linux/nsproxy.h>
#include <linux/ns_common.h>
#include <linux/err.h>
#include <uapi/linux/utsname.h>
enum uts_proc {
UTS_PROC_OSTYPE,
UTS_PROC_OSRELEASE,
UTS_PROC_VERSION,
UTS_PROC_HOSTNAME,
UTS_PROC_DOMAINNAME,
};
struct user_namespace;
extern struct user_namespace init_user_ns;
struct uts_namespace {
struct new_utsname name;
struct user_namespace *user_ns;
struct ucounts *ucounts;
struct ns_common ns;
} __randomize_layout;
extern struct uts_namespace init_uts_ns;
#ifdef CONFIG_UTS_NS
static inline void get_uts_ns(struct uts_namespace *ns)
{
refcount_inc(&ns->ns.count);
}
extern struct uts_namespace *copy_utsname(unsigned long flags,
struct user_namespace *user_ns, struct uts_namespace *old_ns);
extern void free_uts_ns(struct uts_namespace *ns);
static inline void put_uts_ns(struct uts_namespace *ns)
{
if (refcount_dec_and_test(&ns->ns.count))
free_uts_ns(ns);
}
void uts_ns_init(void);
#else
static inline void get_uts_ns(struct uts_namespace *ns)
{
}
static inline void put_uts_ns(struct uts_namespace *ns)
{
}
static inline struct uts_namespace *copy_utsname(unsigned long flags,
struct user_namespace *user_ns, struct uts_namespace *old_ns)
{
if (flags & CLONE_NEWUTS)
return ERR_PTR(-EINVAL);
return old_ns;
}
static inline void uts_ns_init(void)
{
}
#endif
#ifdef CONFIG_PROC_SYSCTL
extern void uts_proc_notify(enum uts_proc proc);
#else
static inline void uts_proc_notify(enum uts_proc proc)
{
}
#endif
static inline struct new_utsname *utsname(void)
{
return &current->nsproxy->uts_ns->name;
}
static inline struct new_utsname *init_utsname(void)
{
return &init_uts_ns.name;
}
extern struct rw_semaphore uts_sem;
#endif /* _LINUX_UTSNAME_H */