linux-kernel - Re: [PATCH v3 1/2] clone3: add CLONE_CLEAR

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Message-ID: <20191021144633.GA2720@redhat.com>
Date:   Mon, 21 Oct 2019 16:46:33 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Christian Brauner <christian.brauner@...ntu.com>
Cc:     linux-kernel@...r.kernel.org, Florian Weimer <fweimer@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, libc-alpha@...rceware.org,
        David Howells <dhowells@...hat.com>,
        Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Roman Gushchin <guro@...com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Aleksa Sarai <cyphar@...har.com>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        linux-kselftest@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH v3 1/2] clone3: add CLONE_CLEAR_SIGHAND

On 10/14, Christian Brauner wrote:
>
> The child helper process on Linux posix_spawn must ensure that no signal
> handlers are enabled, so the signal disposition must be either SIG_DFL
> or SIG_IGN. However, it requires a sigprocmask to obtain the current
> signal mask and at least _NSIG sigaction calls to reset the signal
> handlers for each posix_spawn call

Plus the caller has to block/unblock all signals around clone(VM|VFORK).

Can this justify the new CLONE_ flag? Honestly, I have no idea. But the
patch is simple and looks technically correct to me. FWIW,

Reviewed-by: Oleg Nesterov <oleg@...hat.com>