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From: Greg KH on 11 Aug 2010 20:20
2.6.35-stable review patch. If anyone has any objections, please let us know.

------------------

From: Chris Wright <chrisw(a)sous-sol.org>

commit b7300b78d1a87625975a799a109a2f98d77757c8 upstream.

The cgroup device whitelist code gets confused when trying to grant
permission to a disk partition that is not currently open. Part of
blkdev_open() includes __blkdev_get() on the whole disk.

Basically, the only ways to reliably allow a cgroup access to a partition
on a block device when using the whitelist are to 1) also give it access
to the whole block device or 2) make sure the partition is already open in
a different context.

The patch avoids the cgroup check for the whole disk case when opening a
partition.

Addresses https://bugzilla.redhat.com/show_bug.cgi?id=589662

Signed-off-by: Chris Wright <chrisw(a)sous-sol.org>
Acked-by: Serge E. Hallyn <serue(a)us.ibm.com>
Tested-by: Serge E. Hallyn <serue(a)us.ibm.com>
Reported-by: Vivek Goyal <vgoyal(a)redhat.com>
Cc: Al Viro <viro(a)ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch(a)infradead.org>
Cc: "Daniel P. Berrange" <berrange(a)redhat.com>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

---
fs/block_dev.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1339,10 +1339,12 @@ static int __blkdev_get(struct block_dev
/*
* hooks: /n/, see "layering violations".
*/
- ret = devcgroup_inode_permission(bdev->bd_inode, perm);
- if (ret != 0) {
- bdput(bdev);
- return ret;
+ if (!for_part) {
+ ret = devcgroup_inode_permission(bdev->bd_inode, perm);
+ if (ret != 0) {
+ bdput(bdev);
+ return ret;
+ }
}

lock_kernel();


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