[CRIU] RPC support for --shell-job missing on restore

[Ruslan Kuprieiev]

On 16.05.2014 17:08, Andrew Vagin wrote:
> On Fri, May 16, 2014 at 04:49:16PM +0300, Ruslan Kuprieiev wrote:
>> On 16.05.2014 16:28, Andrew Vagin wrote:
>>> On Fri, May 16, 2014 at 08:33:41AM -0400, Christopher Covington wrote:
>>>> Hi Allan,
>>>>
>>>> On 05/16/2014 03:44 AM, Allan Cecil wrote:
>>>>> On 2014-05-15 06:59, Pavel Emelyanov wrote:
>>>>>> I'd like to notice here, that right now this is only possible if you
>>>>>> terminate the whole existing process and
>>>>>> restore one back from scratch using criu. However, we have a feature
>>>>>> called "applying images" (http://criu.org/Applying_images)
>>>>>> With it you will not have to kill the original process and the
>>>>>> revert-back should become MUCH faster.
>>>>> Applying images sounds very interesting - how do I do that?  I don't see it in
>>>>> the man page.  I've built from source so I can update or switch branches as
>>>>> needed.
>>>>>
>>>>>> You might b einterested in the --exec-cmd option for criu. It causes
>>>>>> criu to call execv() on whatever you want after
>>>>>> restore thus making _your_ code control the restored processes.
>>>>> I haven't figured out how to make this work, yet.  I'll keep experimenting.  I
>>>>> thought it was for saying "restore this into this screen session" but that did
>>>>> not work.
>>>>>
>>>>>>> that would still work.  Unfortunately, even if I set the suid bit and
>>>>>>> attempt to restore from the command line I still get denied
>>>>>>> bgecause the UID / GID doesn't match.
>>>>>> Can you shed more light on this? We tried to make it work like -- if
>>>>>> we have images for user X, then if we restore from
>>>>>> them from suid-ed criu and the user that does so is X as well, then we
>>>>>> allow for that. Has that get broken?
>>>>>>
>>>>> Here are the exact steps I'm taking.  First, I'm running as the unprivileged
>>>>> user named tas:
>>>>> $ id
>>>>> uid=1001(tas) gid=1001(tas) groups=1001(tas),110(kvm),119(nopasswdlogin)
>>>>>
>>>>> I start screen and inside of screen I start nethack.  This produces the
>>>>> following ps axf -o pid,sid,pgid,uid,gid,comm output:
>>>>>
>>>>>   9002  9002  9002  1001    43 screen
>>>>>   9003  9003  9003  1001  1001  \_ bash
>>>>>   9165  9003  9165  1001  1001      \_ nethack
>>>>>
>>>>> If outside of screen I attempt to issue the command criu dump -v4 -t 9002 as
>>>>> the same tas user I get this:
>>>>>
>>>>> (00.014062) Obtaining task stat ... (00.014126) Error (security.c:34): UID/GID
>>>>> mismatch 1001 != (1001,43,43)
>>>> It looks like the session ID isn't matching.
>>> I have reproduce this bug on my host.
>>>
>>> (00.012437) Obtaining task stat ... (00.012592) Error (security.c:34): UID/GID mismatch 1000 != (1000,20,20)
>>>
>>> [avagin at localhost criu]$ ps -C nethack
>>>    PID TTY          TIME CMD
>>> 10962 pts/2    00:00:00 nethack
>>> [avagin at localhost criu]$ cat /proc/10962/status | grep Gid
>>> Gid:	1000	20	20	20
>>>
>>> [avagin at localhost zzz]$ cat /etc/group | grep 20
>>> games:x:20:
>>>
>>> Add Ruslan Kuprieiev in CC. He is the main security specialist in CRIU;)
>> Thanks Andrew. =)
>>
>> If i get it right, there are some typos in check_ids() from security.c:
>> static bool check_ids(unsigned int crid, unsigned int rid, unsigned int eid,
>> unsigned int sid)
>> {
>>      if (crid == 0)
>>          return true;
>>      if (crid == rid && crid == eid && crid == sid) // Here probably should
>> be "||"s instead of "&&"s
>>          return true;
>>
>>      pr_err("UID/GID mismatch %u != (%u,%u,%u)\n", crid, rid, eid, sid);
>>      return false;
>> }
>>
>> Does it look right to you? If so, will send patch.
> Yes, it does. Is it correct that if we can kill a task, we should be
> able to dump it?
Looks correct to me.

> static int kill_ok_by_cred(struct task_struct *t)
> {
>          const struct cred *cred = current_cred();
>          const struct cred *tcred = __task_cred(t);
>
>          if (uid_eq(cred->euid, tcred->suid) ||
>              uid_eq(cred->euid, tcred->uid)  ||
>              uid_eq(cred->uid,  tcred->suid) ||
>              uid_eq(cred->uid,  tcred->uid))
>                  return 1;
>
>          if (ns_capable(tcred->user_ns, CAP_KILL))
>                  return 1;
>
>          return 0;
> }
>

Sorry if I didn't get smth right, but where and why do you want to put 
this function(kill_ok_by_cred)?

>>
>>>>> (00.014137) Error (cr-dump.c:1438): Check uid (pid: 9002) failed
>>>>>
>>>>> For the record, the criu process has the stuid bit set:
>>>>>
>>>>> -rwsr-xr-x 1 root root 779899 Apr 25 14:39 /usr/local/sbin/criu
>>>>>
>>>>> I'm not sure what to make of this.  Thanks for your thoughts,
>>>> Can you try `criu dump` of `setsid nethack` instead of `criu dump -j` of
>>>> `nethack`.
>>>>
>>>> Regards,
>>>> Christopher
>>>>
>>>> -- 
>>>> Employee of Qualcomm Innovation Center, Inc.
>>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>>>> hosted by the Linux Foundation.
>>
>> -- 
>> Signed-off-by: Ruslan Kuprieiev kupruser at gmail.com
>>


-- 
Signed-off-by: Ruslan Kuprieiev kupruser at gmail.com