Re: [PATCH cgroup/for-4.4-fixes] cgroup: make css_set pin its css's to avoid use-afer-free

[Tejun Heo <tj@kernel.org>]

Hello, Daniel.

On Tue, Nov 24, 2015 at 11:31:18AM +0100, Daniel Wagner wrote:
> I still see this one with the patch applied:

Yeap, this is a different one.

> [   19.369455] ------------[ cut here ]------------
> [   19.369851] WARNING: CPU: 1 PID: 1 at kernel/cgroup_pids.c:97 pids_cancel.constprop.6+0x31/0x40()
> [   19.370596] Modules linked in:
> [   19.370916] CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc1+ #29
> [   19.371418] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.2-0-g33fbe13 by qemu-project.org 04/01/2014
> [   19.372542]  ffffffff81f65382 ffff88007c043b90 ffffffff81551ffc 0000000000000000
> [   19.373173]  ffff88007c043bc8 ffffffff810de202 ffff88007a752000 ffff88007a29ab00
> [   19.374144]  ffff88007c043c80 ffff88007a1d8400 0000000000000001 ffff88007c043bd8
> [   19.375185] Call Trace:
> [   19.375506]  [<ffffffff81551ffc>] dump_stack+0x4e/0x82
> [   19.376238]  [<ffffffff810de202>] warn_slowpath_common+0x82/0xc0
> [   19.376975]  [<ffffffff810de2fa>] warn_slowpath_null+0x1a/0x20
> [   19.377765]  [<ffffffff8118e031>] pids_cancel.constprop.6+0x31/0x40
> [   19.378623]  [<ffffffff8118e0fd>] pids_can_attach+0x6d/0xf0
> [   19.379451]  [<ffffffff81188a4c>] cgroup_taskset_migrate+0x6c/0x330
> [   19.380142]  [<ffffffff81188e05>] cgroup_migrate+0xf5/0x190

Can you please describe how to reproduce this one?  If you have a qemu
image which reproduces this, I'd be happy to take a look at it.

Thanks.

-- 
tejun