linux-kernel - Re: [linux-next] BUG triggered in ptraceme

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Date:   Wed, 19 Sep 2018 10:10:56 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Jann Horn <jannh@...gle.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Andrey Vagin <avagin@...tuozzo.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [linux-next] BUG triggered in ptraceme

On Wed, Sep 19, 2018 at 10:07:37AM +0300, Cyrill Gorcunov wrote:
> Hi Oleg! While been testing criu with linux-next we've triggered a BUG.
> https://api.travis-ci.org/v3/job/430308998/log.txt
> 
> [    2.461618] BUG: sleeping function called from invalid context at security/apparmor/include/cred.h:154
> [    2.461794] in_atomic(): 1, irqs_disabled(): 1, pid: 152, name: init
> [    2.461890] 1 lock held by init/152:
> [    2.461981]  #0: 00000000f30c3fda (tasklist_lock){.+.+}, at: ptrace_traceme+0x1c/0x70
> [    2.462114] irq event stamp: 2524
> [    2.462242] hardirqs last  enabled at (2523): [<ffffffff98002922>] do_syscall_64+0x12/0x190
> [    2.462363] hardirqs last disabled at (2524): [<ffffffff98b8b02f>] _raw_write_lock_irq+0xf/0x40
> [    2.462476] softirqs last  enabled at (1904): [<ffffffff98ac79ef>] unix_sock_destructor+0x4f/0xc0
> [    2.462586] softirqs last disabled at (1902): [<ffffffff98ac79ef>] unix_sock_destructor+0x4f/0xc0
> [    2.462697] CPU: 1 PID: 152 Comm: init Not tainted 4.19.0-rc4-next-20180918+ #1
> 
> Which is due to commit
> 
> commit 4b105cbbaf7c06e01c27391957dc3c446328d087
> Author: Oleg Nesterov <oleg@...hat.com>
> Date:   Wed Jun 17 16:27:33 2009 -0700
> 
>     ptrace: do not use task_lock() for attach
> 
> because now after write_lock_irq(&tasklist_lock); apparmor calls for
> traceme and
> 
> static inline struct aa_label *begin_current_label_crit_section(void)
> {
> 	struct aa_label *label = aa_current_raw_label();
> 
> -->	might_sleep();
> 
> Take a look please, once time permit.

Heh, actually not :) It is due to commit

commit 1f8266ff58840d698a1e96d2274189de1bdf7969
Author: Jann Horn <jannh@...gle.com>
Date:   Thu Sep 13 18:12:09 2018 +0200

which introduced might_sleep. Seems it is bad idea to send bug report
without having a cup of coffee at the morning :)