59607db367
The expected course of development for user namespaces targeted capabilities is laid out at https://wiki.ubuntu.com/UserNamespace. Goals: - Make it safe for an unprivileged user to unshare namespaces. They will be privileged with respect to the new namespace, but this should only include resources which the unprivileged user already owns. - Provide separate limits and accounting for userids in different namespaces. Status: Currently (as of 2.6.38) you can clone with the CLONE_NEWUSER flag to get a new user namespace if you have the CAP_SYS_ADMIN, CAP_SETUID, and CAP_SETGID capabilities. What this gets you is a whole new set of userids, meaning that user 500 will have a different 'struct user' in your namespace than in other namespaces. So any accounting information stored in struct user will be unique to your namespace. However, throughout the kernel there are checks which - simply check for a capability. Since root in a child namespace has all capabilities, this means that a child namespace is not constrained. - simply compare uid1 == uid2. Since these are the integer uids, uid 500 in namespace 1 will be said to be equal to uid 500 in namespace 2. As a result, the lxc implementation at lxc.sf.net does not use user namespaces. This is actually helpful because it leaves us free to develop user namespaces in such a way that, for some time, user namespaces may be unuseful. Bugs aside, this patchset is supposed to not at all affect systems which are not actively using user namespaces, and only restrict what tasks in child user namespace can do. They begin to limit privilege to a user namespace, so that root in a container cannot kill or ptrace tasks in the parent user namespace, and can only get world access rights to files. Since all files currently belong to the initila user namespace, that means that child user namespaces can only get world access rights to *all* files. While this temporarily makes user namespaces bad for system containers, it starts to get useful for some sandboxing. I've run the 'runltplite.sh' with and without this patchset and found no difference. This patch: copy_process() handles CLONE_NEWUSER before the rest of the namespaces. So in the case of clone(CLONE_NEWUSER|CLONE_NEWUTS) the new uts namespace will have the new user namespace as its owner. That is what we want, since we want root in that new userns to be able to have privilege over it. Changelog: Feb 15: don't set uts_ns->user_ns if we didn't create a new uts_ns. Feb 23: Move extern init_user_ns declaration from init/version.c to utsname.h. Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Daniel Lezcano <daniel.lezcano@free.fr> Acked-by: David Howells <dhowells@redhat.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
97 lines
1.8 KiB
C
97 lines
1.8 KiB
C
#ifndef _LINUX_UTSNAME_H
|
|
#define _LINUX_UTSNAME_H
|
|
|
|
#define __OLD_UTS_LEN 8
|
|
|
|
struct oldold_utsname {
|
|
char sysname[9];
|
|
char nodename[9];
|
|
char release[9];
|
|
char version[9];
|
|
char machine[9];
|
|
};
|
|
|
|
#define __NEW_UTS_LEN 64
|
|
|
|
struct old_utsname {
|
|
char sysname[65];
|
|
char nodename[65];
|
|
char release[65];
|
|
char version[65];
|
|
char machine[65];
|
|
};
|
|
|
|
struct new_utsname {
|
|
char sysname[__NEW_UTS_LEN + 1];
|
|
char nodename[__NEW_UTS_LEN + 1];
|
|
char release[__NEW_UTS_LEN + 1];
|
|
char version[__NEW_UTS_LEN + 1];
|
|
char machine[__NEW_UTS_LEN + 1];
|
|
char domainname[__NEW_UTS_LEN + 1];
|
|
};
|
|
|
|
#ifdef __KERNEL__
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/kref.h>
|
|
#include <linux/nsproxy.h>
|
|
#include <linux/err.h>
|
|
|
|
struct user_namespace;
|
|
extern struct user_namespace init_user_ns;
|
|
|
|
struct uts_namespace {
|
|
struct kref kref;
|
|
struct new_utsname name;
|
|
struct user_namespace *user_ns;
|
|
};
|
|
extern struct uts_namespace init_uts_ns;
|
|
|
|
#ifdef CONFIG_UTS_NS
|
|
static inline void get_uts_ns(struct uts_namespace *ns)
|
|
{
|
|
kref_get(&ns->kref);
|
|
}
|
|
|
|
extern struct uts_namespace *copy_utsname(unsigned long flags,
|
|
struct uts_namespace *ns);
|
|
extern void free_uts_ns(struct kref *kref);
|
|
|
|
static inline void put_uts_ns(struct uts_namespace *ns)
|
|
{
|
|
kref_put(&ns->kref, free_uts_ns);
|
|
}
|
|
#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 uts_namespace *ns)
|
|
{
|
|
if (flags & CLONE_NEWUTS)
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
return ns;
|
|
}
|
|
#endif
|
|
|
|
static inline struct new_utsname *utsname(void)
|
|
{
|
|
return ¤t->nsproxy->uts_ns->name;
|
|
}
|
|
|
|
static inline struct new_utsname *init_utsname(void)
|
|
{
|
|
return &init_uts_ns.name;
|
|
}
|
|
|
|
extern struct rw_semaphore uts_sem;
|
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
#endif /* _LINUX_UTSNAME_H */
|