FYI, we noticed the below changes on

https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux-security 2015-11-09/cgroupns
commit 17f950075758d56395fb1b1e072ff6a19bbf0422 ("extend cgroup namespaces to legacy hierarchies")


[   45.429443] Freeing unused kernel memory: 3412K (ffffffff823c4000 - ffffffff82719000)
[   45.463197] input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input3
[   50.813394] ------------[ cut here ]------------
[   50.814014] WARNING: CPU: 0 PID: 2342 at kernel/cgroup.c:1008 cset_cgroup_from_root+0x95/0xaf()
[   50.814014] Modules linked in:
[   50.814014] CPU: 0 PID: 2342 Comm: mount Not tainted 4.3.0-03332-g17f9500 #175
[   50.814014] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[   50.814014]  0000000000000000 ffff88000c51b720 ffffffff814f97bc 0000000000000000
[   50.814014]  ffff88000c51b758 ffffffff810929d0 ffffffff8111f539 ffffffff82273a00
[   50.814014]  ffffffff834e8000 ffff88000b83b000 0000000000000000 ffff88000c51b768
[   50.814014] Call Trace:
[   50.814014]  [<ffffffff814f97bc>] dump_stack+0x4b/0x63
[   50.814014]  [<ffffffff810929d0>] warn_slowpath_common+0x99/0xb2
[   50.814014]  [<ffffffff8111f539>] ? cset_cgroup_from_root+0x95/0xaf
[   50.814014]  [<ffffffff81092a9c>] warn_slowpath_null+0x1a/0x1c
[   50.814014]  [<ffffffff8111f539>] cset_cgroup_from_root+0x95/0xaf
[   50.814014]  [<ffffffff8112251e>] cgroup_path_ns+0x2d/0x61
[   50.814014]  [<ffffffff81122580>] cgroup_path+0x2e/0x30
[   50.814014]  [<ffffffff814f3a96>] cfq_get_queue+0x368/0x480
[   50.814014]  [<ffffffff810db46f>] ? lock_acquire+0x113/0x1a1
[   50.814014]  [<ffffffff814f3e29>] ? cfq_set_request+0x5c/0x31e
[   50.814014]  [<ffffffff814f3e29>] ? cfq_set_request+0x5c/0x31e
[   50.814014]  [<ffffffff814f3f01>] cfq_set_request+0x134/0x31e
[   50.814014]  [<ffffffff810d8f55>] ? mark_held_locks+0x5e/0x74
[   50.814014]  [<ffffffff81c23256>] ? _raw_spin_unlock_irq+0x2c/0x3d
[   50.814014]  [<ffffffff810d90e8>] ? trace_hardirqs_on_caller+0x17d/0x199
[   50.814014]  [<ffffffff810d9111>] ? trace_hardirqs_on+0xd/0xf
[   50.814014]  [<ffffffff81c23256>] ? _raw_spin_unlock_irq+0x2c/0x3d
[   50.814014]  [<ffffffff814ce02b>] elv_set_request+0x1c/0x21
[   50.814014]  [<ffffffff814d1e49>] get_request+0x516/0x930
[   50.814014]  [<ffffffff810d0214>] ? wake_up_bit+0x2a/0x2a
[   50.814014]  [<ffffffff814d4ef0>] blk_queue_bio+0x191/0x3b8
[   50.814014]  [<ffffffff814d2ddd>] generic_make_request+0x9c/0xdb
[   50.814014]  [<ffffffff814d2f06>] submit_bio+0xea/0x11e
[   50.814014]  [<ffffffff816db968>] __floppy_read_block_0+0xcb/0x116
[   50.814014]  [<ffffffff810d5ee6>] ? trace_hardirqs_off+0xd/0xf
[   50.814014]  [<ffffffff81c2469a>] ? retint_kernel+0x10/0x10
[   50.814014]  [<ffffffff816db858>] ? floppy_resume+0x3f/0x3f
[   50.814014]  [<ffffffff816dbb08>] floppy_revalidate+0x155/0x18b
[   50.814014]  [<ffffffff81200c0c>] check_disk_change+0x52/0x5e
[   50.814014]  [<ffffffff816dbf3b>] floppy_open+0x2a6/0x315
[   50.814014]  [<ffffffff81201540>] __blkdev_get+0x115/0x3dc
[   50.814014]  [<ffffffff81201ac3>] ? blkdev_get+0x2bc/0x2fd
[   50.814014]  [<ffffffff812019cd>] blkdev_get+0x1c6/0x2fd
[   50.814014]  [<ffffffff811ea7e7>] ? mntput_no_expire+0xdd/0x34d
[   50.814014]  [<ffffffff811eaa84>] ? mntput+0x2d/0x2f
[   50.814014]  [<ffffffff811d54e3>] ? path_put+0x1e/0x21
[   50.814014]  [<ffffffff81201d22>] blkdev_get_by_path+0x38/0x71
[   50.814014]  [<ffffffff811cf4ec>] mount_bdev+0x48/0x19f
[   50.814014]  [<ffffffff8127d4df>] ? ext4_calculate_overhead+0x2bd/0x2bd
[   50.814014]  [<ffffffff81279731>] ext4_mount+0x15/0x17
[   50.814014]  [<ffffffff811d0117>] mount_fs+0x14/0x8c
[   50.814014]  [<ffffffff811e9cb0>] vfs_kern_mount+0x6c/0x13a
[   50.814014]  [<ffffffff811ece66>] do_mount+0xa45/0xbcf
[   50.814014]  [<ffffffff81190e5e>] ? strndup_user+0x3f/0x8c
[   50.814014]  [<ffffffff811ed21b>] SyS_mount+0x75/0xa1
[   50.814014]  [<ffffffff81c23b72>] entry_SYSCALL_64_fastpath+0x12/0x76
[   50.814014] ---[ end trace 033452ab753baa40 ]---
[   50.814014] ------------[ cut here ]------------





Thanks,
Ying Huang