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Date: Fri, 12 May 2017 18:17:06 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: mhocko@suse.com, avagin@openvz.org, peterz@infradead.org,
        linux-kernel@vger.kernel.org, rppt@linux.vnet.ibm.com,
        ebiederm@xmission.com, luto@kernel.org, gorcunov@openvz.org,
        akpm@linux-foundation.org, mingo@kernel.org, serge@hallyn.com
Subject: Re: [PATCH v2] pid_ns: Fix race between setns'ed fork() and
        zap_pid_ns_processes()
Message-ID: <20170512161705.GA18742@redhat.com>
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On 05/12, Kirill Tkhai wrote:
>
 --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1845,11 +1845,13 @@ static __latent_entropy struct task_struct *copy_process(
>  	*/
>  	recalc_sigpending();
>  	if (signal_pending(current)) {
> -		spin_unlock(&current->sighand->siglock);
> -		write_unlock_irq(&tasklist_lock);
>  		retval = -ERESTARTNOINTR;
>  		goto bad_fork_cancel_cgroup;
>  	}
> +	if (unlikely(!(ns_of_pid(pid)->nr_hashed & PIDNS_HASH_ADDING))) {
> +		retval = -ENOMEM;
> +		goto bad_fork_cancel_cgroup;
> +	}
>  
>  	if (likely(p->pid)) {
>  		ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
> @@ -1907,6 +1909,8 @@ static __latent_entropy struct task_struct *copy_process(
>  	return p;
>  
>  bad_fork_cancel_cgroup:
> +	spin_unlock(&current->sighand->siglock);
> +	write_unlock_irq(&tasklist_lock);
>  	cgroup_cancel_fork(p);

Looks good to me.

Oleg.