linux-kernel - Re: [PATCH v8 1/2] seccomp: add a return code to trap to userspace

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Date:   Tue, 30 Oct 2018 17:39:26 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Christian Brauner <christian@...uner.io>,
        Tyler Hicks <tyhicks@...onical.com>,
        Akihiro Suda <suda.akihiro@....ntt.co.jp>,
        Aleksa Sarai <asarai@...e.de>, linux-kernel@...r.kernel.org,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v8 1/2] seccomp: add a return code to trap to userspace

On 10/30, Oleg Nesterov wrote:
>
> On 10/30, Tycho Andersen wrote:
> >
> > @@ -828,6 +823,11 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
> >  	 */
> >  	rmb();
> >
> > +	if (!sd) {
> > +		populate_seccomp_data(&sd_local);
> > +		sd = &sd_local;
> > +	}
> > +
>
> To me it would be more clean to remove the "if (!sd)" check, case(SECCOMP_RET_TRACE)
> in __seccomp_filter() can simply do populate_seccomp_data(&sd_local) unconditionally
> and pass &sd_local to __seccomp_filter().

Ah, please ignore, emulate_vsyscall() does secure_computing(NULL).

Btw. why __seccomp_filter() doesn't return a boolean?

Or at least, why can't case(SECCOMP_RET_TRACE) simply do

	return __seccomp_filter(this_syscall, NULL, true);

?

Oleg.