linux-kernel - Re: [PATCH] umh: fix UAF when the process is being killed

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Date:   Wed, 14 Dec 2022 10:28:11 +0800
From:   Schspa Shi <schspa@...il.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org,
        syzbot+10d19d528d9755d9af22@...kaller.appspotmail.com,
        syzbot+70d5d5d83d03db2c813d@...kaller.appspotmail.com,
        syzbot+83cb0411d0fcf0a30fc1@...kaller.appspotmail.com
Subject: Re: [PATCH] umh: fix UAF when the process is being killed


Luis Chamberlain <mcgrof@...nel.org> writes:

> On Mon, Dec 12, 2022 at 09:38:31PM +0800, Schspa Shi wrote:
>> I'd like to upload a V2 patch with the new solution if you prefer the
>> following way.
>> 
>> diff --git a/kernel/umh.c b/kernel/umh.c
>> index 850631518665..8023f11fcfc0 100644
>> --- a/kernel/umh.c
>> +++ b/kernel/umh.c
>> @@ -452,6 +452,11 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
>>                 /* umh_complete() will see NULL and free sub_info */
>>                 if (xchg(&sub_info->complete, NULL))
>>                         goto unlock;
>> +               /*
>> +                * kthreadd (or new kernel thread) will call complete()
>> +                * shortly.
>> +                */
>> +               wait_for_completion(&done);
>>         }
>
> Yes much better. Did you verify it fixes the splat found by the bots?
>

Yes, it will fix it.

>   Luis


-- 
BRs
Schspa Shi