From: Eric W. Biederman <ebiederm@xmission.com>
Date: Fri, 27 Jul 2012 13:21:27 +0000 (-0700)
Subject: userns: Allow setting a userns mapping to your current uid.
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=37657da3c5d4a3bbbbb9d3b78f53a8134a0abae0;p=linux-beck.git

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 456a6b9fba34..49096d559e08 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -709,6 +709,21 @@ ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t
 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;