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From: "izbyshev at ispras dot ru" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug libc/29115] vfork()-based posix_spawn() has more failure modes
 than fork()-based one
Date: Mon, 02 May 2022 20:56:47 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29115

--- Comment #7 from Alexey Izbyshev <izbyshev at ispras dot ru> ---
(In reply to Carlos O'Donell from comment #5)
> Either the kernel supports vfork or it doesn't.
>=20
> A time namespace, or a seccomp filter are all the same problems, and we
> should return the error the userspace.
>=20
> Adding code which will only be exercised in the event that a time namespa=
ce
> is in use is going to result in increased long-term maintenance costs.
>=20
> It also results in unexpected surprise behaviour when the developer runs
> under a time namespace e.g. more memory usage, different code paths taken
> etc.
>=20
> Rather than add long-term maintenance and surprise developers my suggesti=
on
> is to fail the posix_spawn.
>=20
posix_spawn() failing and fork()/exec() not failing is also a surprise for
developers. Note that if users are expected to deal with this posix_spawn()
failure, all language frameworks/libraries providing high level process
creation APIs will have to implement knobs to opt-out from posix_spawn(). I=
t's
not clear to me that it's better than a potential performance problem due to
fork() when time namespaces are used.

We also don't know what other vfork() failure modes that fork() doesn't have
may appear in the future. A fallback would cover them.

--=20
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