linux-kernel - Re: [PATCH v2] pid_ns: Fix race between setns'ed fork() and zap_pid_ns

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Message-ID: <20170512161705.GA18742@redhat.com>
Date:   Fri, 12 May 2017 18:17:06 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     mhocko@...e.com, avagin@...nvz.org, peterz@...radead.org,
        linux-kernel@...r.kernel.org, rppt@...ux.vnet.ibm.com,
        ebiederm@...ssion.com, luto@...nel.org, gorcunov@...nvz.org,
        akpm@...ux-foundation.org, mingo@...nel.org, serge@...lyn.com
Subject: Re: [PATCH v2] pid_ns: Fix race between setns'ed fork() and
        zap_pid_ns_processes()

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.