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mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-25 21:54:06 +08:00
linux-next/include/linux/pid_namespace.h
Alexey Gladkov fa10fed30f proc: allow to mount many instances of proc in one pid namespace
This patch allows to have multiple procfs instances inside the
same pid namespace. The aim here is lightweight sandboxes, and to allow
that we have to modernize procfs internals.

1) The main aim of this work is to have on embedded systems one
supervisor for apps. Right now we have some lightweight sandbox support,
however if we create pid namespacess we have to manages all the
processes inside too, where our goal is to be able to run a bunch of
apps each one inside its own mount namespace without being able to
notice each other. We only want to use mount namespaces, and we want
procfs to behave more like a real mount point.

2) Linux Security Modules have multiple ptrace paths inside some
subsystems, however inside procfs, the implementation does not guarantee
that the ptrace() check which triggers the security_ptrace_check() hook
will always run. We have the 'hidepid' mount option that can be used to
force the ptrace_may_access() check inside has_pid_permissions() to run.
The problem is that 'hidepid' is per pid namespace and not attached to
the mount point, any remount or modification of 'hidepid' will propagate
to all other procfs mounts.

This also does not allow to support Yama LSM easily in desktop and user
sessions. Yama ptrace scope which restricts ptrace and some other
syscalls to be allowed only on inferiors, can be updated to have a
per-task context, where the context will be inherited during fork(),
clone() and preserved across execve(). If we support multiple private
procfs instances, then we may force the ptrace_may_access() on
/proc/<pids>/ to always run inside that new procfs instances. This will
allow to specifiy on user sessions if we should populate procfs with
pids that the user can ptrace or not.

By using Yama ptrace scope, some restricted users will only be able to see
inferiors inside /proc, they won't even be able to see their other
processes. Some software like Chromium, Firefox's crash handler, Wine
and others are already using Yama to restrict which processes can be
ptracable. With this change this will give the possibility to restrict
/proc/<pids>/ but more importantly this will give desktop users a
generic and usuable way to specifiy which users should see all processes
and which users can not.

Side notes:
* This covers the lack of seccomp where it is not able to parse
arguments, it is easy to install a seccomp filter on direct syscalls
that operate on pids, however /proc/<pid>/ is a Linux ABI using
filesystem syscalls. With this change LSMs should be able to analyze
open/read/write/close...

In the new patch set version I removed the 'newinstance' option
as suggested by Eric W. Biederman.

Selftest has been added to verify new behavior.

Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Reviewed-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2020-04-22 10:51:21 -05:00

92 lines
2.1 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PID_NS_H
#define _LINUX_PID_NS_H
#include <linux/sched.h>
#include <linux/bug.h>
#include <linux/mm.h>
#include <linux/workqueue.h>
#include <linux/threads.h>
#include <linux/nsproxy.h>
#include <linux/kref.h>
#include <linux/ns_common.h>
#include <linux/idr.h>
/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
#define MAX_PID_NS_LEVEL 32
struct fs_pin;
struct pid_namespace {
struct kref kref;
struct idr idr;
struct rcu_head rcu;
unsigned int pid_allocated;
struct task_struct *child_reaper;
struct kmem_cache *pid_cachep;
unsigned int level;
struct pid_namespace *parent;
#ifdef CONFIG_BSD_PROCESS_ACCT
struct fs_pin *bacct;
#endif
struct user_namespace *user_ns;
struct ucounts *ucounts;
int reboot; /* group exit code if this pidns was rebooted */
struct ns_common ns;
} __randomize_layout;
extern struct pid_namespace init_pid_ns;
#define PIDNS_ADDING (1U << 31)
#ifdef CONFIG_PID_NS
static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
{
if (ns != &init_pid_ns)
kref_get(&ns->kref);
return ns;
}
extern struct pid_namespace *copy_pid_ns(unsigned long flags,
struct user_namespace *user_ns, struct pid_namespace *ns);
extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);
extern int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd);
extern void put_pid_ns(struct pid_namespace *ns);
#else /* !CONFIG_PID_NS */
#include <linux/err.h>
static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
{
return ns;
}
static inline struct pid_namespace *copy_pid_ns(unsigned long flags,
struct user_namespace *user_ns, struct pid_namespace *ns)
{
if (flags & CLONE_NEWPID)
ns = ERR_PTR(-EINVAL);
return ns;
}
static inline void put_pid_ns(struct pid_namespace *ns)
{
}
static inline void zap_pid_ns_processes(struct pid_namespace *ns)
{
BUG();
}
static inline int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
{
return 0;
}
#endif /* CONFIG_PID_NS */
extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
void pidhash_init(void);
void pid_idr_init(void);
#endif /* _LINUX_PID_NS_H */