linux-kernel - Re: [Bug 215813] syscall(SYS_vfork) causes execve() to return 0. (was: vfork(2) behavior not consistent with fork(2))

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Message-ID: <5e3946e1-f4bb-e3f8-11e9-be26589972b6@gmail.com>
Date:   Wed, 6 Apr 2022 21:31:57 +0200
From:   Alejandro Colomar <alx.manpages@...il.com>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     Christian Brauner <brauner@...nel.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        linux-kernel@...r.kernel.org,
        Коренберг Марк 
        <socketpair@...il.com>, Andrei Vagin <avagin@...nvz.org>,
        Dmitry Safonov <dima@...sta.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>, Serge Hallyn <serge@...lyn.com>,
        linux-api@...r.kernel.org, bugzilla-daemon@...nel.org
Subject: Re: [Bug 215813] syscall(SYS_vfork) causes execve() to return 0.
 (was: vfork(2) behavior not consistent with fork(2))

Hi Florian,

On 4/6/22 21:26, Florian Weimer wrote:
> It's not clear if this is valid.  The syscall function in glibc does not
> protect the on-stack return address against overwriting, so it can't be
> used to call SYS_vfork on x86.
> 
> Can you reproduce this with a true inline syscall, or the glibc vfork
> function (which protects the return address)?

If you tell me how I can call a syscall without the libc wrapper or 
syscall(2), sure, I can try :)

If syscall(2) can't be used for certain syscalls, maybe we should 
document that.

Thanks,

Alex