* 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]
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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
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