On 05/23/2017 09:32 AM, Greg Kurz wrote:
> When using the mapped-file security, credentials are stored in a metadata
> directory located in the parent directory. This is okay for all paths with
> the notable exception of the root path, since we don't want and probably
> can't create a metadata directory above the virtfs directory on the host.
>
> This patch introduces a dedicated metadata file, sitting in the virtfs root
> for this purpose. It relies on the fact that the "." name necessarily refers
> to the virtfs root.
>
> As for the metadata directory, we don't want the client to see this file.
> The current code only cares for readdir() but there are many other places
> to fix actually. The filtering logic is hence put in a separate function.
>
> @@ -478,7 +504,8 @@ static off_t local_telldir(FsContext *ctx,
> V9fsFidOpenState *fs)
>
> static bool local_is_mapped_file_metadata(FsContext *fs_ctx, const char
> *name)
> {
> - return !strcmp(name, VIRTFS_META_DIR);
> + return
> + !strcmp(name, VIRTFS_META_DIR) || !strcmp(name,
> VIRTFS_META_ROOT_FILE);We have to block VIRTFS_META_DIR at any depth in the hierarchy, but can/should we change the blocking of VIRTFS_META_ROOT_FILE to only happen at the root directory, rather than at all directories? On the other hand, if you can simultaneously map /path/to/a for one mount point, and /path/to/a/b for another, then the root file for B is visible at a lower depth than the root file for A, and blocking the metafile name everywhere means that the mount A can't influence the behavior on the mount for B. Not tested, but looks sane, so: Reviewed-by: Eric Blake <ebl...@redhat.com> -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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