Re: [Virtio-fs] virtiofs mounted filesystems & SELinux

On Thu, Jun 03, 2021 at 10:14:24PM -0400, Link Dupont wrote: > On Thu, Jun 3 2021 at 08:56:46 PM -0400, Link Dupont <link(a)sub-pop.net&gt; > wrote: > > reproducible scenarios > > Alright. I reran my tests with a CentOS 8 guest. On CentOS 8 (with a > virtiofs filesystem and with xattr on), the type of files in the mounted > hierarchy are unlabeled_t. I can work around that by switching SELinux in > the guest to permissive or disabled. cc Dan Walsh. I was discussing this with Dan Walsh yesterday in general. In general, if we want to enable SELinux both on host and guest, then both host and guest should have same SELinux policy. Otherwise there will be lot of different kind of conflicts because both host and guest will try to work with same selinux label. I guess that in practice this will be very hard to achieve as people will run different host and guest flavors and these might have different policies.

So another option is to rename selinux xattr in virtiofs so that any selinux xattr coming from guest is saved as user.virtiofs.security.selinux xattr on host. That way host and guest can have their separate labels without interfering with each other. David Gilbert already has added support for this. I can't remember the exact syntax but you can figure it out from documentation here in xattr remappig section.

https://github.com/qemu/qemu/blob/master/docs/tools/virtiofsd.rst But I have question with selinux xattr remapping. What will happen to initial labels when fs is exported. I mean until and unless some process in guest labels all the exported files, they all with either be unlabeled or pick some generic label for all the files.

Another option is, can we use a single label for whole of the virtiofs (using context=<label>) option in guest. That way nothing is saved in files as such. But this means that processes in guest can't have different selinux labels on different virtiofs dir/files.

Dan, what do you think? Thanks Vivek > > With a CentOS 7 guest, things get less usable. I digested this to a > reproducible scenario. > > Build a disk image with `virt-builder`, configuring the CentOS Plus kernel > to get 9p support. > > virt-builder centos-7.8 \ > --root-password password:centos \ > --output centos-7.8.qcow2 \ > --install yum-utils \ > --run-command 'yum-config-manager --enable centosplus' \ > --run-command 'sed -ie "s/DEFAULTKERNEL=kernel/DEFAULTKERNEL=kernel-plus/" > /etc/sysconfig/kernel' \ > --append-line '/etc/dracut.conf.d/virtio.conf:add_drivers+="virtio_scsi > virtio_pci virtio_console"' \ > --append-line '/etc/modules-load.d/9pnet_virtio.conf:9pnet_virtio' \ > --install kernel-plus \ > --append-line '/etc/fstab:home /home 9p trans=virtio,version=9p2000.L 0 0' > > Install the volume into the `default` pool. > > sudo install -m644 centos-7.8.qcow2 /var/lib/libvirt/images > > Next, define a domain using the disk image (using `virt-install` here for > "easy mode"). > > virt-install \ > --import \ > --os-variant centos7.0 \ > --name centos \ > --ram 2048 \ > --disk path=/var/lib/libvirt/images/centos-7.8.qcow2 \ > --memorybacking access.mode=shared \ > --filesystem source=/home,target=home,accessmode=passthrough \ > --autoconsole none > > Now with SELinux enforcing, I cannot list the contents of the directories in > the mounted hierarchy. > > [root@localhost ~]# ls -lZ /home/link > ls: cannot open directory /home/link: Permission denied > > > > _______________________________________________ > Virtio-fs mailing list > Virtio-fs(a)redhat.com > https://listman.redhat.com/mailman/listinfo/virtio-fs >