From 7db9cfd380205f6b50afdc3bc3619f876a5eaf0d Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@openvz.org>
Date: Thu, 5 Jun 2008 22:46:27 -0700
Subject: [PATCH] devscgroup: check for device permissions at mount time

Currently even if a task sits in an all-denied cgroup it can still mount
any block device in any mode it wants.

Put a proper check in do_open for block device to prevent this.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Tested-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 fs/block_dev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7d822fae7765..470c10ceb0fb 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -12,6 +12,7 @@
 #include <linux/kmod.h>
 #include <linux/major.h>
 #include <linux/smp_lock.h>
+#include <linux/device_cgroup.h>
 #include <linux/highmem.h>
 #include <linux/blkdev.h>
 #include <linux/module.h>
@@ -928,9 +929,14 @@ static int do_open(struct block_device *bdev, struct file *file, int for_part)
 {
 	struct module *owner = NULL;
 	struct gendisk *disk;
-	int ret = -ENXIO;
+	int ret;
 	int part;
 
+	ret = devcgroup_inode_permission(bdev->bd_inode, file->f_mode);
+	if (ret != 0)
+		return ret;
+
+	ret = -ENXIO;
 	file->f_mapping = bdev->bd_inode->i_mapping;
 	lock_kernel();
 	disk = get_gendisk(bdev->bd_dev, &part);
-- 
2.20.1