linux-kernel - Re: [PATCH v10 1/2] fork: extend clone3() to support setting a PID

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Message-ID: <20191115130800.zntefr5ptabdngph@wittgenstein>
Date:   Fri, 15 Nov 2019 14:08:01 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Andrei Vagin <avagin@...il.com>, Adrian Reber <areber@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Pavel Emelyanov <ovzxemul@...il.com>,
        Jann Horn <jannh@...gle.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, Mike Rapoport <rppt@...ux.ibm.com>,
        Radostin Stoyanov <rstoyanov1@...il.com>
Subject: Re: [PATCH v10 1/2] fork: extend clone3() to support setting a PID

On Fri, Nov 15, 2019 at 11:49:10AM +0100, Oleg Nesterov wrote:
> On 11/15, Christian Brauner wrote:
> >
> > +static int set_tid_next(pid_t *set_tid, size_t *size, int idx)
> > +{
> > +	int tid = 0;
> > +
> > +	if (*size) {
> > +		tid = set_tid[idx];
> > +		if (tid < 1 || tid >= pid_max)
> > +			return -EINVAL;
> > +
> > +		/*
> > +		 * Also fail if a PID != 1 is requested and
> > +		 * no PID 1 exists.
> > +		 */
> > +		if (tid != 1 && !tmp->child_reaper)
> > +			return -EINVAL;
> > +
> > +		if (!ns_capable(tmp->user_ns, CAP_SYS_ADMIN))
> > +			return -EPERM;
> > +
> > +		(*size)--;
> > +	}
> 
> this needs more args, struct pid_namespace *tmp + pid_t pid_max
> 		if (set_tid_size) {
> 			tid = set_tid[ns->level - i];
> 
> 			retval = -EINVAL;
> 			if (tid < 1 || tid >= pid_max)
> 				goto out_free;

I'm not a fan of this pattern of _not_ setting error codes in the actual
error path t but I won't object.

	Christian