Re: [CFT][PATCH 09/10] sysfs: Create mountpoints with sysfs_create_empty_dir

On Tue, Aug 11, 2015 at 11:57 AM, Eric W. Biederman
[off-list ref] wrote:

Tejun Heo [off-list ref] writes:

quoted

On Thu, May 14, 2015 at 12:36:30PM -0500, Eric W. Biederman wrote:

quoted

This allows for better documentation in the code and
it allows for a simpler and fully correct version of
fs_fully_visible to be written.

The mount points converted and their filesystems are:
/sys/hypervisor/s390/       s390_hypfs
/sys/kernel/config/         configfs
/sys/kernel/debug/          debugfs
/sys/firmware/efi/efivars/  efivarfs
/sys/fs/fuse/connections/   fusectl
/sys/fs/pstore/             pstore
/sys/kernel/tracing/        tracefs
/sys/fs/cgroup/             cgroup
/sys/kernel/security/       securityfs
/sys/fs/selinux/            selinuxfs
/sys/fs/smackfs/            smackfs

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <redacted>

So, this somehow ends up confusing upstart on centos6 based systems
making it fail to mount tmpfs on /sys/fs/cgroup.  It also skips sunrpc
and other mounts are different too.  No idea why at this point.  Can
we please revert this from -stable until we know what's going on?

*Boggle*

The only time this should prevent anything is when in a container when
you are not global root.  And then only mounting sysfs should be
affected.

Before:

open("/sys/kernel/debug/asdf", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK,
0666) = -1 EACCES (Permission denied)


After:

open("/sys/kernel/debug/asdf", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK,
0666) = -1 ENOENT (No such file or directory)

Something broke.  I don't know whether CentOS cares about that change,
but there could be other odd side effects.

--Andy