[libvirt] [PATCH v3 04/12] LXC: introduce virLXCControllerSetupUserns and lxcContainerSetID

[Gao feng]

On 06/04/2013 09:35 PM, Daniel P. Berrange wrote:
> On Thu, May 23, 2013 at 12:06:48PM +0800, Gao feng wrote:
>> This patch introduces new helper function
>> virLXCControllerSetupUserns, in this function,
>> we set the files uid_map and gid_map of the init
>> task of container.
>>
>> lxcContainerSetID is used for creating cred for
>> tasks running in container. Since after setuid/setgid,
>> we may be a new user. This patch calls lxcContainerSetUserns
>> at first to make sure the new created files belong to
>> right user.
>>
>> Signed-off-by: Gao feng <gaofeng at cn.fujitsu.com>
>> ---
>>  src/lxc/lxc_container.c  | 63 ++++++++++++++++++++++++++++++++--------------
>>  src/lxc/lxc_controller.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 110 insertions(+), 18 deletions(-)
>>
>> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
>> index 618252c..52fcf39 100644
>> --- a/src/lxc/lxc_container.c
>> +++ b/src/lxc/lxc_container.c
>> @@ -335,6 +335,30 @@ int lxcContainerWaitForContinue(int control)
>>  
>>  
>>  /**
>> + * lxcContainerSetID:
>> + *
>> + * This function calls setuid and setgid to create proper
>> + * cred for tasks running in container.
>> + *
>> + * Returns 0 on success or -1 in case of error
>> + */
>> +static int lxcContainerSetID(virDomainDefPtr def)
>> +{
>> +    /* Only call virSetUIDGID when user namespace is enabled
>> +     * for this container. And user namespace is only enabled
>> +     * when nuidmap&ngidmap is not zero */
>> +
>> +    if (def->idmap.nuidmap && virSetUIDGID(0, 0) < 0) {
>> +        virReportSystemError(errno, "%s",
>> +                             _("setuid or setgid failed"));
>> +        return -1;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +
>> +/**
>>   * lxcContainerRenameAndEnableInterfaces:
>>   * @nveths: number of interfaces
>>   * @veths: interface names
>> @@ -1937,6 +1961,27 @@ static int lxcContainerChild(void *data)
>>      cmd = lxcContainerBuildInitCmd(vmDef);
>>      virCommandWriteArgLog(cmd, 1);
>>  
>> +    if (lxcContainerResolveSymlinks(vmDef) < 0)
>> +        goto cleanup;
>> +
>> +    if (!virFileExists(vmDef->os.init)) {
>> +        virReportSystemError(errno,
>> +                    _("cannot find init path '%s' relative to container root"),
>> +                    vmDef->os.init);
>> +        goto cleanup;
>> +    }
>> +
>> +    /* Wait for interface devices to show up */
>> +    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
>> +        virReportSystemError(errno, "%s",
>> +                             _("Failed to read the container continue message"));
>> +        goto cleanup;
>> +    }
>> +    VIR_DEBUG("Received container continue message");
>> +
>> +    if (lxcContainerSetID(vmDef) < 0)
>> +        goto cleanup;
>> +
>>      root = virDomainGetRootFilesystem(vmDef);
>>  
>>      if (argv->nttyPaths) {
>> @@ -1962,29 +2007,11 @@ static int lxcContainerChild(void *data)
>>          goto cleanup;
>>      }
>>  
>> -    if (lxcContainerResolveSymlinks(vmDef) < 0)
>> -        goto cleanup;
>> -
>>      if (lxcContainerSetupPivotRoot(vmDef, root,
>>                                     argv->ttyPaths, argv->nttyPaths,
>>                                     argv->securityDriver) < 0)
>>          goto cleanup;
>>  
>> -    if (!virFileExists(vmDef->os.init)) {
>> -        virReportSystemError(errno,
>> -                    _("cannot find init path '%s' relative to container root"),
>> -                    vmDef->os.init);
>> -        goto cleanup;
>> -    }
>> -
>> -    /* Wait for interface devices to show up */
>> -    if (lxcContainerWaitForContinue(argv->monitor) < 0) {
>> -        virReportSystemError(errno, "%s",
>> -                             _("Failed to read the container continue message"));
>> -        goto cleanup;
>> -    }
>> -    VIR_DEBUG("Received container continue message");
> 
> Why did you need to move these functions before the lxcContainerSetID
> call ?

lxcContainerSetID is only meaningful after we set idmap for user namespace,
Actually I just move lxcContainerSetID to the top of lxcContainerChild.
It's better to call setuid/setgid as early as we can.


> 
>> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
>> index dfe686b..0a2e3ac 100644
>> --- a/src/lxc/lxc_controller.c
>> +++ b/src/lxc/lxc_controller.c
>> @@ -1122,6 +1122,68 @@ cleanup2:
>>  }
>>  
>>  
>> +static int
>> +virLXCControllerSetupUsernsMap(virDomainIdMapEntryPtr map,
>> +                               char *path,
>> +                               int num)
>> +{
>> +    virBuffer map_value = VIR_BUFFER_INITIALIZER;
>> +    int i, ret = -1;
>> +
>> +    for (i = 0; i < num; i++)
>> +        virBufferAsprintf(&map_value, "%u %u %u\n",
>> +                          map[i].start, map[i].target, map[i].count);
>> +
> 
> You need to check
> 
>   virBufferError()
> 
> to see if OOM has occured here.
> 

sure,
I will wait for your related patches being merged and then update this patchset.

Thanks
Gao

>> +    if (virFileWriteStr(path, virBufferCurrentContent(&map_value), 0) < 0) {
>> +        virReportSystemError(errno, _("unable write to %s"), path);
>> +        goto cleanup;
>> +    }
>> +    ret = 0;
>> +
>> +cleanup:
>> +    virBufferFreeAndReset(&map_value);
>> +    return ret;
>> +}
> 
> 
> Daniel
>