[RFC][PATCH] ns: Syscalls for better namespace sharing control.

[Daniel Lezcano]

Eric W. Biederman wrote:
> Daniel Lezcano <daniel.lezcano at free.fr> writes:
>
>   
>> Eric W. Biederman wrote:
>>     
>>> Daniel Lezcano <daniel.lezcano at free.fr> writes:
>>>
>>>   
>>>       
>>>> Eric W. Biederman wrote:
>>>>     
>>>>         
>>>>> I have take an snapshot of my development tree and placed it at.
>>>>>
>>>>>
>>>>> git://git.kernel.org/pub/scm/linux/people/ebiederm/linux-2.6.33-nsfd-v5.git
>>>>>         
>>>>>           
>>>> Hi Eric,
>>>>
>>>> thanks for the pointer.
>>>>
>>>> I tried to boot the kernel under qemu and I got this oops:
>>>>     
>>>>         
>>> I am clearly running an old userspace on my test machine.  No udev.
>>> It looks like udev has a long standing netlink misfeature, where
>>> it does not initializing NETLINK_CB....
>>>
>>>
>>> >From 8d85e3ab88718eda3d94cf8e1be14b69dae2b8f1 Mon Sep 17 00:00:00 2001
>>> From: Eric W. Biederman <ebiederm at xmission.com>
>>> Date: Mon, 8 Mar 2010 09:25:20 -0800
>>> Subject: [PATCH] kobject_uevent:  Use the netlink allocator helper...
>>>
>>> Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
>>>   
>>>       
>> Thanks.
>>
>> I was able to boot but I have the following warning:
>>     
>
> Thanks for the bug report.
>   
Thanks to you for the patchset :)

> For the moment you might want to drop:
> af_netlink:  Allow credentials to work across namespaces.
> af_netlink: Debugging in case I have missed something.
>
> Although I am curious if you hit my debugging messages in
> netlink recv.
>   
No, it does not appear (looked for "missing NETLINK_CB proto").

> I guess if the goal is to test my nsfd bits you can drop everything
> starting with my 'scm: Reorder scm_cookie.' commit.  The rest is what
> it takes to get get uids, gid and pids translated when the cross
> namespaces on an af_unix of an af_netlink socket.
>
> At least in the af_netlink case it appears clear I am have missed
> something.
>
> This is a warning that netlink throws when the packet accounting messed
> up.  So it sounds like you are exercising another path that I failed
> to exercise and fix.
>   
I will look forward if I find more clues for this warning.

In the meantime  was able to enter the container with the ugly following 
program:

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <syscall.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/param.h>

#define __NR_setns 300

int setns(int nstype, int fd)
{
    return syscall (__NR_setns, nstype, fd);
}

int main(int argc, char *argv[])
{
    char path[MAXPATHLEN];
    char *ns[] = { "pid", "mnt", "net", "pid", "uts" };
    const int size = sizeof(ns) / sizeof(char *);
    int fd[size];
    int i;

    if (argc != 3) {
        fprintf(stderr, "mynsenter <pid> <command>\n");
        exit(1);
    }

    for (i = 0; i < size; i++) {
       
        sprintf(path, "/proc/%s/ns/%s", argv[1], ns[i]);

        fd[i] = open(path, O_RDONLY);
        if (fd[i] < 0) {
            perror("open");
            return -1;
        }

    }

    for (i = 0; i < size; i++) {

        if (setns(0, fd[i])) {
            perror("setns");
            return -1;
        }
    }

    execve(argv[2], &argv[2], NULL);
    perror("execve");

    return 0;
}

At the fist glance, no problem :)