From 5c1469de7545a35a16ff2b902e217044a7d2f8a5 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 13 Jun 2010 03:28:03 +0000 Subject: 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 Acked-by: Serge E. Hallyn Signed-off-by: David S. Miller --- kernel/user_namespace.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) (limited to 'kernel') diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index b2d70d38dff4..25915832291a 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -9,6 +9,7 @@ #include #include #include +#include #include /* @@ -82,3 +83,46 @@ void free_user_ns(struct kref *kref) schedule_work(&ns->destroyer); } EXPORT_SYMBOL(free_user_ns); + +uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid) +{ + struct user_namespace *tmp; + + if (likely(to == cred->user->user_ns)) + return uid; + + + /* Is cred->user the creator of the target user_ns + * or the creator of one of it's parents? + */ + for ( tmp = to; tmp != &init_user_ns; + tmp = tmp->creator->user_ns ) { + if (cred->user == tmp->creator) { + return (uid_t)0; + } + } + + /* No useful relationship so no mapping */ + return overflowuid; +} + +gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid) +{ + struct user_namespace *tmp; + + if (likely(to == cred->user->user_ns)) + return gid; + + /* Is cred->user the creator of the target user_ns + * or the creator of one of it's parents? + */ + for ( tmp = to; tmp != &init_user_ns; + tmp = tmp->creator->user_ns ) { + if (cred->user == tmp->creator) { + return (gid_t)0; + } + } + + /* No useful relationship so no mapping */ + return overflowgid; +} -- cgit v1.2.3