2022-03-31 15:18:06

by Марк Коренберг

Subject: BUG: vfork() returns EINVAL after unshare(CLONE_NEWTIME)

test:
----------------------------------------
#define _GNU_SOURCE 1
#include <stdio.h>
#include <sched.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <err.h>

#ifndef CLONE_NEWTIME
#define CLONE_NEWTIME 0x00000080
#endif

int main (void)
{
if (unshare (CLONE_NEWTIME)) err (EXIT_FAILURE, "UNSHARE_NEWTIME");

pid_t pid;
switch (pid=vfork ())
{
case 0:
_exit(0);
case -1:
err(EXIT_FAILURE, "vfork BUG");
default:
waitpid(pid, NULL, 0);
}
return 0;
}
-----------------------------------------------

Seems the bug in kernel/fork.c. It does not check for CLONE_VFORK

if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
if (nsp->time_ns != nsp->time_ns_for_children)
return ERR_PTR(-EINVAL);
}

-----------------------------------
Changing vfork() to fork() in the program works ok.
The bug has been found during regression in our system because Python
3.10 runs subprocesses using vfork()+execve().

--
Segmentation fault

2022-05-04 20:59:48

by Randy Dunlap

Subject: Re: BUG: vfork() returns EINVAL after unshare(CLONE_NEWTIME)

[add some readers:]

On 3/31/22 01:36, Марк Коренберг wrote:
> test:
> ----------------------------------------
> #define _GNU_SOURCE 1
> #include <stdio.h>
> #include <sched.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <sys/types.h>
> #include <sys/wait.h>
> #include <err.h>
>
> #ifndef CLONE_NEWTIME
> #define CLONE_NEWTIME 0x00000080
> #endif
>
> int main (void)
> {
> if (unshare (CLONE_NEWTIME)) err (EXIT_FAILURE, "UNSHARE_NEWTIME");
>
> pid_t pid;
> switch (pid=vfork ())
> {
> case 0:
> _exit(0);
> case -1:
> err(EXIT_FAILURE, "vfork BUG");
> default:
> waitpid(pid, NULL, 0);
> }
> return 0;
> }
> -----------------------------------------------
>
> Seems the bug in kernel/fork.c. It does not check for CLONE_VFORK
>
> if (clone_flags & (CLONE_THREAD | CLONE_VM)) {
> if (nsp->time_ns != nsp->time_ns_for_children)
> return ERR_PTR(-EINVAL);
> }
>
> -----------------------------------
> Changing vfork() to fork() in the program works ok.
> The bug has been found during regression in our system because Python
> 3.10 runs subprocesses using vfork()+execve().
>

--
~Randy