user_ns: Introduce user_nsmap_uid and user_ns_map_gid.
Define what happens when a we view a uid from one user_namespace
in another user_namepece.
- If the user namespaces are the same no mapping is necessary.
- For most cases of difference use overflowuid and overflowgid,
the uid and gid currently used for 16bit apis when we have a 32bit uid
that does fit in 16bits. Effectively the situation is the same,
we want to return a uid or gid that is not assigned to any user.
- For the case when we happen to be mapping the uid or gid of the
creator of the target user namespace use uid 0 and gid as confusing
that user with root is not a problem.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index cc4f453..8178156 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -36,6 +36,9 @@
kref_put(&ns->kref, free_user_ns);
}
+uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid);
+gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid);
+
#else
static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
@@ -52,6 +55,17 @@
{
}
+static inline uid_t user_ns_map_uid(struct user_namespace *to,
+ const struct cred *cred, uid_t uid)
+{
+ return uid;
+}
+static inline gid_t user_ns_map_gid(struct user_namespace *to,
+ const struct cred *cred, gid_t gid)
+{
+ return gid;
+}
+
#endif
#endif /* _LINUX_USER_H */