From 8a5d927a5337b1c9a0c8478c4e522ce0ded09b85 Mon Sep 17 00:00:00 2001
From: "Guillaume J. Charmes" <charmes.guillaume@gmail.com>
Date: Wed, 27 Nov 2013 18:21:17 -0800
Subject: [PATCH] Check if the target loopback is a block device

---
 graphdriver/devmapper/attachLoopback.go | 5 +++--
 graphdriver/devmapper/sys.go            | 7 ++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/graphdriver/devmapper/attachLoopback.go b/graphdriver/devmapper/attachLoopback.go
index 98d0bf5f5b..0d556d81c2 100644
--- a/graphdriver/devmapper/attachLoopback.go
+++ b/graphdriver/devmapper/attachLoopback.go
@@ -39,8 +39,9 @@ func openNextAvailableLoopback(index int, sparseFile *osFile) (loopFile *osFile,
 			return nil, ErrAttachLoopbackDevice
 		}
 
-		// FIXME: Check here if target is a block device (in C: S_ISBLK(mode))
-		if fi.IsDir() {
+		if fi.Mode()&osModeDevice != osModeDevice {
+			utils.Errorf("Loopback device %s is not a block device.", target)
+			continue
 		}
 
 		// Open the targeted loopback (use OpenFile because Open sets O_CLOEXEC)
diff --git a/graphdriver/devmapper/sys.go b/graphdriver/devmapper/sys.go
index 152e68285b..9cf124a9a5 100644
--- a/graphdriver/devmapper/sys.go
+++ b/graphdriver/devmapper/sys.go
@@ -46,9 +46,10 @@ const (
 	sysSysIoctl = syscall.SYS_IOCTL
 	sysEBusy    = syscall.EBUSY
 
-	osORdOnly = os.O_RDONLY
-	osORdWr   = os.O_RDWR
-	osOCreate = os.O_CREATE
+	osORdOnly    = os.O_RDONLY
+	osORdWr      = os.O_RDWR
+	osOCreate    = os.O_CREATE
+	osModeDevice = os.ModeDevice
 )
 
 func toSysStatT(i interface{}) *sysStatT {