userns: Allow setting a userns mapping to your current uid.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 456a6b9..49096d5 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -709,6 +709,21 @@
static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
struct uid_gid_map *new_map)
{
+ /* Allow mapping to your own filesystem ids */
+ if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1)) {
+ u32 id = new_map->extent[0].lower_first;
+ if (cap_setid == CAP_SETUID) {
+ kuid_t uid = make_kuid(ns->parent, id);
+ if (uid_eq(uid, current_fsuid()))
+ return true;
+ }
+ else if (cap_setid == CAP_SETGID) {
+ kgid_t gid = make_kgid(ns->parent, id);
+ if (gid_eq(gid, current_fsgid()))
+ return true;
+ }
+ }
+
/* Allow anyone to set a mapping that doesn't require privilege */
if (!cap_valid(cap_setid))
return true;