linux-api.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* vfork(2) behavior not consistent with fork(2) (was: vfork(2) fails after unshare(CLONE_NEWTIME) (was: [Bug 215769] man 2 vfork() does not document corner case when PID == 1))
       [not found]         ` <20220406084613.3srklyt27qxcmrcx@wittgenstein>
@ 2022-04-06 19:22           ` Alejandro Colomar
  2022-04-06 19:26             ` vfork(2) behavior not consistent with fork(2) Florian Weimer
  0 siblings, 1 reply; 3+ messages in thread
From: Alejandro Colomar @ 2022-04-06 19:22 UTC (permalink / raw)
  To: Christian Brauner, Florian Weimer, Michael Kerrisk
  Cc: linux-kernel,
	Коренберг Марк,
	Andrei Vagin, Dmitry Safonov, Thomas Gleixner, Arnd Bergmann,
	Serge Hallyn, bugzilla-daemon, linux-api

> $ sudo ./vfork_newpid
> vfork_newpid: PID: 8479
> vfork_newpid: PID 8479 exiting after execve(2): Success
> print_pid: PID 1 exiting. 


I definitely think this is a kernel (or glibc) bug.
execve(2) is supposed to _never_ return 0 (and errno 0).
I submitted a new bug to discuss it.

Please see <https://bugzilla.kernel.org/show_bug.cgi?id=215813>

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: vfork(2) behavior not consistent with fork(2)
  2022-04-06 19:22           ` vfork(2) behavior not consistent with fork(2) (was: vfork(2) fails after unshare(CLONE_NEWTIME) (was: [Bug 215769] man 2 vfork() does not document corner case when PID == 1)) Alejandro Colomar
@ 2022-04-06 19:26             ` Florian Weimer
  2022-04-06 19:31               ` [Bug 215813] syscall(SYS_vfork) causes execve() to return 0. (was: vfork(2) behavior not consistent with fork(2)) Alejandro Colomar
  0 siblings, 1 reply; 3+ messages in thread
From: Florian Weimer @ 2022-04-06 19:26 UTC (permalink / raw)
  To: Alejandro Colomar
  Cc: Christian Brauner, Michael Kerrisk, linux-kernel,
	Коренберг Марк,
	Andrei Vagin, Dmitry Safonov, Thomas Gleixner, Arnd Bergmann,
	Serge Hallyn, bugzilla-daemon, linux-api

* Alejandro Colomar:

>> $ sudo ./vfork_newpid
>> vfork_newpid: PID: 8479
>> vfork_newpid: PID 8479 exiting after execve(2): Success
>> print_pid: PID 1 exiting. 
>
>
> I definitely think this is a kernel (or glibc) bug.
> execve(2) is supposed to _never_ return 0 (and errno 0).
> I submitted a new bug to discuss it.
>
> Please see <https://bugzilla.kernel.org/show_bug.cgi?id=215813>

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)?

Thanks,
Florian


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [Bug 215813] syscall(SYS_vfork) causes execve() to return 0. (was: vfork(2) behavior not consistent with fork(2))
  2022-04-06 19:26             ` vfork(2) behavior not consistent with fork(2) Florian Weimer
@ 2022-04-06 19:31               ` Alejandro Colomar
  0 siblings, 0 replies; 3+ messages in thread
From: Alejandro Colomar @ 2022-04-06 19:31 UTC (permalink / raw)
  To: Florian Weimer
  Cc: Christian Brauner, Michael Kerrisk, linux-kernel,
	Коренберг Марк,
	Andrei Vagin, Dmitry Safonov, Thomas Gleixner, Arnd Bergmann,
	Serge Hallyn, linux-api, bugzilla-daemon

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

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-04-06 21:02 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <bug-215769-216477@https.bugzilla.kernel.org/>
     [not found] ` <bug-215769-216477-to2O9X1Knw@https.bugzilla.kernel.org/>
     [not found]   ` <4fb02f5f-60f9-42af-ddd5-fe5af877231f@gmail.com>
     [not found]     ` <20220404080519.pi6izyuop3mmdg2g@wittgenstein>
     [not found]       ` <ae2cbf67-aace-bc40-418e-7b41873f814a@gmail.com>
     [not found]         ` <20220406084613.3srklyt27qxcmrcx@wittgenstein>
2022-04-06 19:22           ` vfork(2) behavior not consistent with fork(2) (was: vfork(2) fails after unshare(CLONE_NEWTIME) (was: [Bug 215769] man 2 vfork() does not document corner case when PID == 1)) Alejandro Colomar
2022-04-06 19:26             ` vfork(2) behavior not consistent with fork(2) Florian Weimer
2022-04-06 19:31               ` [Bug 215813] syscall(SYS_vfork) causes execve() to return 0. (was: vfork(2) behavior not consistent with fork(2)) Alejandro Colomar

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).