userns: Convert binder ipc to use kuids

Cc: Arve Hjønnevåg <arve@android.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

drivers/staging/android/binder.c

@@ -47,7 +47,7 @@ static HLIST_HEAD(binder_dead_nodes);
 static struct dentry *binder_debugfs_dir_entry_root;
 static struct dentry *binder_debugfs_dir_entry_proc;
 static struct binder_node *binder_context_mgr_node;
-static uid_t binder_context_mgr_uid = -1;
+static kuid_t binder_context_mgr_uid = INVALID_UID;
 static int binder_last_id;
 static struct workqueue_struct *binder_deferred_workqueue;
 
@@ -356,7 +356,7 @@ struct binder_transaction {
 	unsigned int	flags;
 	long	priority;
 	long	saved_priority;
-	uid_t	sender_euid;
+	kuid_t	sender_euid;
 };
 
 static void
@@ -2427,7 +2427,7 @@ retry:
 		}
 		tr.code = t->code;
 		tr.flags = t->flags;
-		tr.sender_euid = t->sender_euid;
+		tr.sender_euid = from_kuid(current_user_ns(), t->sender_euid);
 
 		if (t->from) {
 			struct task_struct *sender = t->from->proc->tsk;
@@ -2705,12 +2705,12 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			ret = -EBUSY;
 			goto err;
 		}
-		if (binder_context_mgr_uid != -1) {
-			if (binder_context_mgr_uid != current->cred->euid) {
+		if (uid_valid(binder_context_mgr_uid)) {
+			if (!uid_eq(binder_context_mgr_uid, current->cred->euid)) {
 				pr_err("binder: BINDER_SET_"
 				       "CONTEXT_MGR bad uid %d != %d\n",
-				       current->cred->euid,
-				       binder_context_mgr_uid);
+				       from_kuid(&init_user_ns, current->cred->euid),
+				       from_kuid(&init_user_ns, binder_context_mgr_uid));
 				ret = -EPERM;
 				goto err;
 			}

init/Kconfig

@@ -952,9 +952,6 @@ config UIDGID_CONVERTED
 	depends on UFS_FS = n
 	depends on XFS_FS = n
 
-	# The rare drivers that won't build
-	depends on ANDROID_BINDER_IPC = n
-
 config UIDGID_STRICT_TYPE_CHECKS
 	bool "Require conversions between uid/gids and their internal representation"
 	depends on UIDGID_CONVERTED