Re: [Qemu-devel] [PATCH 5/5] 9pfs: local: forbid client access to metadata

[Eric Blake]

On 05/05/2017 09:37 AM, Greg Kurz wrote:
> When using the mapped-file security mode, we shouldn't let the client
> mess with the metadata. The current code already hides it but the
> client can still access the metadata through several operations.
> 
> This patch fixes the issue by:
> - preventing the creation of fids pointing to the metadata (name_to_path)
> - failing various operations taking a dirpath and a name arguments if
>   name is a metadata reserved name
> 
> Signed-off-by: Greg Kurz <address@hidden>
> ---
>  hw/9pfs/9p-local.c |   41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> index b427d2928800..93cadac302c9 100644
> --- a/hw/9pfs/9p-local.c
> +++ b/hw/9pfs/9p-local.c
> @@ -588,6 +588,11 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath 
> *dir_path,
>      int err = -1;
>      int dirfd;
>  
> +    if (local_must_skip_metadata(fs_ctx, name)) {
> +        errno = EINVAL;
> +        return -1;
> +    }
> +

I don't know if EINVAL is the best error, but it seems reasonable enough.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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