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Re: [Qemu-devel] [PATCH 4/5] 9pfs: local: metadata file for the VirtFS r
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 4/5] 9pfs: local: metadata file for the VirtFS root |
Date: |
Fri, 5 May 2017 12:11:14 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.0 |
On 05/05/2017 09:37 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 refer
s/refer/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.
>
> Before:
>
> # ls -ld
> drwxr-xr-x. 3 greg greg 4096 May 5 12:49 .
> # chown root.root .
> chown: changing ownership of '.': Is a directory
> # ls -ld
> drwxr-xr-x. 3 greg greg 4096 May 5 12:49 .
>
> After:
>
> # ls -ld
> drwxr-xr-x. 3 greg greg 4096 May 5 12:49 .
> # chown bin.bin .
> # ls -ld
> drwxr-xr-x. 3 root root 4096 May 5 12:50 .
Huh? How does chown bin.bin result in root.root? Copy-and-paste error?
>
> and from the host:
>
> ls -al .virtfs_metadata_root
> -rwx------. 1 greg greg 26 May 5 12:50 .virtfs_metadata_root
> $ cat .virtfs_metadata_root
> virtfs.uid=0
> virtfs.gid=0
So what happens if the guest tries to manipulate
./.virtfs_metadata_root? I know you are filtering it so that readdir()
and such can't see it, but do you have sane errors for the guest's
attempt to circumvent those hidden names?
>
> Reported-by: Léo Gaspard <address@hidden>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> hw/9pfs/9p-local.c | 88
> ++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 61 insertions(+), 27 deletions(-)
>
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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- Re: [Qemu-devel] [PATCH 2/5] 9pfs: local: resolve special directories in paths, (continued)
[Qemu-devel] [PATCH 3/5] 9pfs: local: simplify file opening, Greg Kurz, 2017/05/05
[Qemu-devel] [PATCH 4/5] 9pfs: local: metadata file for the VirtFS root, Greg Kurz, 2017/05/05
- Re: [Qemu-devel] [PATCH 4/5] 9pfs: local: metadata file for the VirtFS root,
Eric Blake <=
[Qemu-devel] [PATCH 5/5] 9pfs: local: forbid client access to metadata, Greg Kurz, 2017/05/05
Re: [Qemu-devel] [PATCH 0/5] 9pfs: local: fix metadata of mapped-file security mode, no-reply, 2017/05/05
Re: [Qemu-devel] [PATCH 0/5] 9pfs: local: fix metadata of mapped-file security mode, Leo Gaspard, 2017/05/08