linux-kernel - Re: [PATCH 2/2] memcg: Close the race between migration and installing bprm->mm as mm

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Date:   Wed, 9 May 2018 16:51:52 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, peterz@...radead.org,
        viro@...iv.linux.org.uk, mingo@...nel.org,
        paulmck@...ux.vnet.ibm.com, keescook@...omium.org, riel@...hat.com,
        tglx@...utronix.de, kirill.shutemov@...ux.intel.com,
        marcos.souza.org@...il.com, hoeun.ryu@...il.com,
        pasha.tatashin@...cle.com, gs051095@...il.com, dhowells@...hat.com,
        rppt@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
        Balbir Singh <balbir@...ux.vnet.ibm.com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/2] memcg: Close the race between migration and
 installing bprm->mm as mm

On 05/04, Eric W. Biederman wrote:
>
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1044,6 +1044,8 @@ static int exec_mmap(struct mm_struct *mm)
>  		return 0;
>  	}
>  	mmdrop(active_mm);
> +	/* The tsk may have migrated before the new mm was attached */
> +	mm_sync_memcg_from_task(tsk);
>  	return 0;
>  }

call_usermodehelper(). perhaps it makes sense to change flush_old_exec()
to clear PF_KTHREAD/etc before exec_mmap().

Oleg.