linux-kernel - Re: [syzbot] WARNING: locking bug in umh

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Message-ID: <6c47dbcf-2a17-6bb2-719b-841d851c603b@I-love.SAKURA.ne.jp>
Date:   Fri, 3 Feb 2023 21:59:51 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org, mcgrof@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+6cd18e123583550cf469@...kaller.appspotmail.com>,
        Hillf Danton <hdanton@...a.com>
Subject: Re: [syzbot] WARNING: locking bug in umh_complete

On 2023/02/03 21:30, Peter Zijlstra wrote:
>> I think the right fix is to:
>>
>> 	state &= ~TASK_KILLABLE;
> 
> 	state &= ~__TASK_WAKEKILL;
> 
> we don't want to mask out UNINTERUPTIBLE, that would be bad.

This code was made killable as a solution for CVE-2012-4398.
Although OOM reaper is available today, making back to unkillable is not smart.

> 
>> 	wait_for_completion_state(&done, state);
>>
>> Also, put in a comment..