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

[Ruslan Kuprieiev]

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.


>>> (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