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

[Christopher Covington]

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.

> (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

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