[lxc-devel] [PATCH] lxc-start-ephemeral: Fix broken mount logic

[Serge Hallyn]

Quoting Stéphane Graber (stgraber at ubuntu.com):
> This reworks the mount logic for lxc-start-ephemeral to be as follow:
>  - Any real (non-bind) entry gets copied to the target fstab
>  - Any bind-mount from a virtual fs gets copied to the target fstab
>  - Any remaining bind-mount if confirmed to be valid gets setup as an
>    overlay.
> 
> Extra bind-mounts passed through the -b option are mounted by the
> pre-mount script and don't need processing by the fstab generator.
> 
> Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>

Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>

> ---
>  src/lxc/lxc-start-ephemeral.in | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/src/lxc/lxc-start-ephemeral.in b/src/lxc/lxc-start-ephemeral.in
> index af8da80..0f0c398 100644
> --- a/src/lxc/lxc-start-ephemeral.in
> +++ b/src/lxc/lxc-start-ephemeral.in
> @@ -164,30 +164,32 @@ if orig.get_config_item("lxc.mount"):
>                  line.replace(orig.get_config_item("lxc.rootfs"),
>                               dest.get_config_item("lxc.rootfs"))
>  
> -                # Skip any line that's not a bind mount
>                  fields = line.split()
> +
> +                # Skip invalid entries
>                  if len(fields) < 4:
> +                    continue
> +
> +                # Non-bind mounts are kept as-is
> +                if "bind" not in fields[3]:
>                      dest_fd.write("%s\n" % line)
>                      continue
>  
> -                if fields[2] != "bind" and "bind" not in fields[3]:
> +                # Bind mounts of virtual filesystems are also kept as-is
> +                src_path = fields[0].split("/")
> +                if len(src_path) > 1 and src_path[1] in ("proc", "sys"):
>                      dest_fd.write("%s\n" % line)
>                      continue
>  
> -                # Process any remaining line
> +                # Skip invalid mount points
>                  dest_mount = os.path.abspath(os.path.join("%s/rootfs/" % (
>                                               dest_path), fields[1]))
>  
> -                if dest_mount == os.path.abspath("%s/rootfs/%s" % (
> -                                                 dest_path, args.bdir)):
> -
> -                    dest_fd.write("%s\n" % line)
> -                    continue
> -
>                  if "%s/rootfs/" % dest_path not in dest_mount:
>                      print(_("Skipping mount entry '%s' as it's outside "
>                              "of the container rootfs.") % line)
>  
> +                # Setup an overlay for anything remaining
>                  overlay_dirs += [(fields[0], dest_mount)]
>  
>  # Generate pre-mount script
> -- 
> 1.8.3.2
> 
> 
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