linux-kernel - RE: [PATCH] clone3: validate stack arguments

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Message-ID: <c600032527d24cf2a7dfd8a81467fd6f@AcuMS.aculab.com>
Date:   Thu, 31 Oct 2019 11:41:06 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christian Brauner' <christian.brauner@...ntu.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Florian Weimer <fweimer@...hat.com>,
        GNU C Library <libc-alpha@...rceware.org>
CC:     Arnd Bergmann <arnd@...db.de>, Kees Cook <keescook@...omium.org>,
        "Jann Horn" <jannh@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH] clone3: validate stack arguments

From: Christian Brauner
> Sent: 31 October 2019 11:36
...
> /* Intentional user visible API change */
> clone3() was released with 5.3. Currently, it is not documented and very
> unclear to userspace how the stack and stack_size argument have to be
> passed. After talking to glibc folks we concluded that trying to change
> clone3() to setup the stack instead of requiring userspace to do this is
> the right course of action.

What happens if someone 'accidentally' runs a program compiled for
the new API on a system running the existing 5.3 kernel?

While it won't work, it needs to die reasonably gracefully.

	David

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