On Thu, Aug 22, 2013 at 10:10 AM, Oleg Nesterov <o...@redhat.com> wrote:
> 8382fcac "pidns: Outlaw thread creation after unshare(CLONE_NEWPID)"
> nacks CLONE_NEWPID if the forking process unshared pid_ns. This is
> correct but unnecessary, copy_pid_ns() does the same check.
>
> Test-case (needs root or CLONE_NEWUSER should be added):
>
> static int child(void *arg)
> {
> return 0;
> }
>
> static char stack[16 * 1024];
>
> int main(void)
> {
> pid_t pid;
>
> assert(unshare(CLONE_NEWPID) == 0);
>
> pid = clone(child, stack + sizeof(stack) / 2,
> CLONE_NEWPID | SIGCHLD, NULL);
> assert(pid < 0 && errno == EINVAL);
>
> return 0;
> }
>
> clone(CLONE_NEWPID) correctly fails with or without this change.
Acked-by: Andy Lutomirski <l...@amacapital.net>
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
> ---
> kernel/fork.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 86f5376..8d56338 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1176,7 +1176,7 @@ static struct task_struct *copy_process(unsigned long
> clone_flags,
> * If the new process will be in a different pid namespace don't
> * allow the creation of threads, or share the signal handlers.
> */
> - if ((clone_flags & (CLONE_SIGHAND | CLONE_NEWPID)) &&
> + if ((clone_flags & CLONE_SIGHAND) &&
> (task_active_pid_ns(current) != current->nsproxy->pid_ns))
> return ERR_PTR(-EINVAL);
>
> --
> 1.5.5.1
>
--
Andy Lutomirski
AMA Capital Management, LLC
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