xfs: xfs_ioctl: fix information leak to userland

al_hreq is copied from userland.  If al_hreq.buflen is not properly aligned
then xfs_attr_list will ignore the last bytes of kbuf.  These bytes are
unitialized.  It leads to leaking of contents of kernel stack memory.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/linux-2.6/xfs_ioctl.c

@@ -416,7 +416,7 @@ xfs_attrlist_by_handle(
 	if (IS_ERR(dentry))
 		return PTR_ERR(dentry);
 
-	kbuf = kmalloc(al_hreq.buflen, GFP_KERNEL);
+	kbuf = kzalloc(al_hreq.buflen, GFP_KERNEL);
 	if (!kbuf)
 		goto out_dput;