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



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 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 ?

> 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.

> +    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
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