[libvirt] [PATCH] lxc: Set max uid/gid mappings for user namespace

[Daniel P. Berrangé]

On Sat, Dec 15, 2018 at 10:02:34AM +0000, Radostin Stoyanov wrote:
> There is a limit on the number of lines in the /proc/<pid>/{g,u}id_map
> files. In Linux 4.14 and earlier, this limit was (arbitrarily) set at
> 5 lines. Since Linux 4.15, which was released on 28 Jan 2018, the limit
> is 340 lines.
> 
> This change is documented in user_namespaces(7).
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6397fac4915ab3002dc15aae751455da1a852f25
> 
> Signed-off-by: Radostin Stoyanov <rstoyanov1 at gmail.com>
> ---
>  src/lxc/lxc_controller.c | 7 +++++++
>  1 file changed, 7 insertions(+)

Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>


> 
> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
> index 99360397a7..2bec8846aa 100644
> --- a/src/lxc/lxc_controller.c
> +++ b/src/lxc/lxc_controller.c
> @@ -1390,6 +1390,13 @@ virLXCControllerSetupUsernsMap(virDomainIdMapEntryPtr map,
>      size_t i;
>      int ret = -1;
> 
> +    /* The kernel supports up to 340 lines in /proc/<pid>/{g,u}id_map */
> +    if (num > 340) {
> +        virReportError(VIR_ERR_INVALID_ARG, "%s",
> +                       _("Too many id mappings defined."));
> +        goto cleanup;
> +    }
> +
>      for (i = 0; i < num; i++)
>          virBufferAsprintf(&map_value, "%u %u %u\n",
>                            map[i].start, map[i].target, map[i].count);
> --
> 2.19.2
> 
> --
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Regards,
Daniel
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