On Fri, Nov 03, 2023 at 08:55:19AM +0100, Maxime Coquelin wrote: > > > On 11/2/23 19:59, Michael S. Tsirkin wrote: > > On Thu, Nov 02, 2023 at 06:56:59PM +0100, Maxime Coquelin wrote: > > > > > > > > > On 10/24/23 17:30, Casey Schaufler wrote: > > > > On 10/24/2023 2:49 AM, Maxime Coquelin wrote: > > > > > > > > > > > > > > > On 10/23/23 17:13, Casey Schaufler wrote: > > > > > > On 10/23/2023 12:28 AM, Maxime Coquelin wrote: > > > > > > > > > > > > > > > > > > > > > On 10/21/23 00:20, Casey Schaufler wrote: > > > > > > > > On 10/20/2023 8:58 AM, Maxime Coquelin wrote: > > > > > > > > > This patch introduces LSM hooks for devices creation, > > > > > > > > > destruction and opening operations, checking the > > > > > > > > > application is allowed to perform these operations for > > > > > > > > > the Virtio device type. > > > > > > > > > > > > > > > > Why do you think that there needs to be a special LSM check for virtio > > > > > > > > devices? What can't existing device attributes be used? > > > > > > > > > > > > > > Michael asked for a way for SELinux to allow/prevent the creation of > > > > > > > some types of devices [0]. > > > > > > > > > > > > > > A device is created using ioctl() on VDUSE control chardev. Its type is > > > > > > > specified via a field in the structure passed in argument. > > > > > > > > > > > > > > I didn't see other way than adding dedicated LSM hooks to achieve this, > > > > > > > but it is possible that their is a better way to do it? > > > > > > > > > > > > At the very least the hook should be made more general, and I'd have to > > > > > > see a proposal before commenting on that. security_dev_destroy(dev) > > > > > > might > > > > > > be a better approach. If there's reason to control destruction of vduse > > > > > > devices it's reasonable to assume that there are other devices with the > > > > > > same or similar properties. > > > > > > > > > > VDUSE is different from other devices as the device is actually > > > > > implemented by the user-space application, so this is very specific in > > > > > my opinion. > > > > > > > > This is hardly unique. If you're implementing the device > > > > in user-space you may well be able to implement the desired > > > > controls there. > > > > > > > > > > > > > > > > > > > > > Since SELinux is your target use case, can you explain why you can't > > > > > > create SELinux policy to enforce the restrictions you're after? I > > > > > > believe > > > > > > (but can be proven wrong, of course) that SELinux has mechanism for > > > > > > dealing > > > > > > with controls on ioctls. > > > > > > > > > > > > > > > > I am not aware of such mechanism to deal with ioctl(), if you have a > > > > > pointer that would be welcome. > > > > > > > > security/selinux/hooks.c > > > > > > We might be able to extend selinux_file_ioctl(), but that will only > > > covers the ioctl for the control file, this patch also adds hook for the > > > device file opening that would need dedicated hook as the device type > > > information is stored in the device's private data. > > > > > > Michael, before going further, I would be interested in your feedback. > > > Was this patch what you had in mind when requesting for a way to > > > allow/deny devices types for a given application? > > > > > > Regards, > > > Maxime > > > > > > Yes, this is more or less what I had in mind. > > Great. > > Do you think we need to cover both ioctl() on the control file and > open() on the device file, or only ioctl() is enough? > > If the former, we will need VDUSE-specific hooks. I may be able to > improve my patch to have a single hook instead of 3 by passing the type > of operation as an extra argument (create/destroy/open). > > If the latter, we may be able to extend the generic ioctl hook. > > Personally, I think it would make sense to also ensure a given > application can only open existing VDUSE devices it supports. For > example, openvswitch should only be allowed to open networking VDUSE > devices. > > Thanks, > Maxime I agree here. I think an open hook is important. Make sure to document the need in the cover letter and commit log. > > > > > > > > > > > > > > > > Thanks, > > > > > Maxime > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > Maxime > > > > > > > > > > > > > > [0]: > > > > > > > https://lore.kernel.org/all/20230829130430-mutt-send-email-mst@xxxxxxxxxx/ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
