linux-kernel - Re: [PATCH 2/4] pid: add pidfd

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Date:   Wed, 27 Mar 2019 18:21:24 +0100
From:   Yann Droneaud <ydroneaud@...eya.com>
To:     Christian Brauner <christian@...uner.io>, jannh@...gle.com,
        khlebnikov@...dex-team.ru, luto@...nel.org, dhowells@...hat.com,
        serge@...lyn.com, ebiederm@...ssion.com, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     arnd@...db.de, keescook@...omium.org, adobriyan@...il.com,
        tglx@...utronix.de, mtk.manpages@...il.com, bl0pbl33p@...il.com,
        ldv@...linux.org, akpm@...ux-foundation.org, oleg@...hat.com,
        nagarathnam.muthusamy@...cle.com, cyphar@...har.com,
        viro@...iv.linux.org.uk, joel@...lfernandes.org, dancol@...gle.com
Subject: Re: [PATCH 2/4] pid: add pidfd_open()

Le mercredi 27 mars 2019 à 17:21 +0100, Christian Brauner a écrit :

> diff --git a/kernel/pid.c b/kernel/pid.c
> index 20881598bdfa..c9e24e726aba 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -26,8 +26,10 @@
> +SYSCALL_DEFINE4(pidfd_open, pid_t, pid, int, procfd, int, pidfd,
> unsigned int,
> +		flags)
> +{
> +	long fd = -EINVAL;
> +
> +	if (flags & ~(PIDFD_TO_PROCFD | PROCFD_TO_PIDFD))
> +		return -EINVAL;
> +
> +	if (!flags) {
> +		struct pid *pidfd_pid;
> +
> +		if (pid <= 0)
> +			return -EINVAL;
> +
> +		if (procfd != -1 || pidfd != -1)
> +			return -EINVAL;
> +
> +		rcu_read_lock();
> +		pidfd_pid = get_pid(find_pid_ns(pid, task_active_pid_ns(current)));
> +		rcu_read_unlock();
> +
> +		fd = pidfd_create_fd(pidfd_pid, O_CLOEXEC);
> +		put_pid(pidfd_pid);
> +	} else if (flags & PIDFD_TO_PROCFD) {

[...]

> +	} else if (flags & PROCFD_TO_PIDFD) {
> +		if (flags & ~PROCFD_TO_PIDFD)
> +			return -EINVAL;
> +
> +		if (pid != -1)
> +			return -EINVAL;
> +
> +		if (pidfd >= 0)
> 

I think it can be stricter with:

                if (pidfd != -1)

(and match the check done for flag == 0).

Regards.

-- 
Yann Droneaud
OPTEYA