linux-kernel - Re: [PATCH v3 4/7] selftests: add memfd

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Message-ID: <CANq1E4QF0-2e=ZDFvZkjRGunNaqSZ98D2Ah50bUqdgGcDXaPnQ@mail.gmail.com>
Date:	Sat, 19 Jul 2014 18:31:26 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Ryan Lortie <desrt@...rt.ca>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Greg Kroah-Hartman <greg@...ah.com>,
	John Stultz <john.stultz@...aro.org>,
	Lennart Poettering <lennart@...ttering.net>,
	Daniel Mack <zonque@...il.com>, Kay Sievers <kay@...y.org>,
	Tony Battersby <tonyb@...ernetics.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v3 4/7] selftests: add memfd_create() + sealing tests

Hi

On Wed, Jul 16, 2014 at 12:07 PM, Hugh Dickins <hughd@...gle.com> wrote:
> On Fri, 13 Jun 2014, David Herrmann wrote:
>
>> Some basic tests to verify sealing on memfds works as expected and
>> guarantees the advertised semantics.
>>
>> Signed-off-by: David Herrmann <dh.herrmann@...il.com>
>
> Thanks for whatever the fix was, I didn't hit any problem running
> this version repeatedly, on 64-bit and on 32-bit.

glibc does pid-caching so getpid() can be skipped once called. fork()
and clone() have to update it, though. Therefore, you shouldn't mix
fork() and clone() in the same process. I replaced my fork() call with
a simple clone() and the bug was gone.

Thanks
David
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