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

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Message-ID: <m2h6v7ilo6.fsf@gmail.com>
Date:   Mon, 27 Feb 2023 15:57:36 +0800
From:   Schspa Shi <schspa@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Ingo Molnar <mingo@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.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


Peter Zijlstra <peterz@...radead.org> writes:

> On Tue, Feb 14, 2023 at 10:31:58AM +0800, Schspa Shi wrote:
>> Peter Zijlstra <peterz@...radead.org> writes:
>
>> > If so, perhaps the simplest rule would to be ensure there is an
>> > unconditional uninterruptible wait-for-completion() before going out of
>> > scope.
>> >
>> > This latter can be spelled like wait_for_completion() or
>> > wait_for_completion_state(TASK_UNINTERRUPTIBLE). More specifically,
>> > TASK_INTERRUPTIBLE and TASK_WAKEKILL must not be set in the state mask
>> > for the wait to be uninterruptible.
>> >
>> > If it cannot be proven, raise a warning and audit or somesuch.
>> 
>> This is a good suggestion. I have written a SmPL patch to complete this
>> check, and now I need to rule out the situation that the driver has
>> added an additional lock to protect it.
>> 
>> And I have found a lot of bad usage, should we consider adding a new
>> helper API to simplify the fix this?
>
> Please first share some of the locations where this would be applied.

Hi Peter:

I started a new thread to discuss the SmPL patch.

Link: https://lore.kernel.org/all/20230227075346.69658-1-schspa@gmail.com/

-- 
BRs
Schspa Shi