Date: Tue, 03 May 2022 00:49:16 +0300 From: Alexey Izbyshev <izbyshev@...ras.ru> To: musl@...ts.openwall.com Cc: Florian Weimer <fweimer@...hat.com>, Rich Felker <dalias@...c.org>, Andrei Vagin <avagin@...nvz.org>, Christian Brauner <brauner@...nel.org> Subject: Re: vfork()-based posix_spawn() has more failure modes than fork()-based one On 2022-05-03 00:31, Carlos O'Donell wrote: > On 5/2/22 17:25, Florian Weimer wrote: >> * Rich Felker: >> >>> I'm trying to understand how this comes to be. The child should >>> inherit the namespaces of the parent and thus should not be in a >>> different namespace that precludes spawn. I'm guessing this is some >>> oddity where unshare doesn't affect the process itself, only its >>> children? If so, it seems like a bug that it doesn't affect the >>> process itself after execve (after unshare(1) runs your test >>> program), >>> but that probably can't be fixed now on the Linux side for stability >>> reasons. :( >> >> It's about fundamentally conflicting requirements. >> >> The vDSO data mapping needs to store the time offset, so it has to be >> distinct from the original namespace. vfork preserves the VM sharing. >> It's not possible to do both things at the same time. >> >> unshare(CLONE_NEWTIME) should have been specified to only take effect >> after execve, when the vDSO is remapped anyway. > > Can we ask some kernel developers for an opinion? Christian Brauner had some comments [1,2] on this. Time namespaces were added in  by Andrei Vagin. Adding both to CC. Alexey  https://bugzilla.kernel.org/show_bug.cgi?id=215769#c6  https://bugzilla.kernel.org/show_bug.cgi?id=215769#c10  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=769071ac9f20b6a447410c7eaa55d1a5233ef40c
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