82b1bec6b0
Add support for creating block devices using the `crosvm devices` command. Due to conflicting seccomp policies between vhost-user transport and the block device, we need to temporarily remove some lines from vhost_user.policy and vvu.policy and reproduce them in the serial device's policy. This will be handled properly later using a new seccomp policy parser. BUG=b:217480043 TEST=`crosvm devices --block vhost=/tmp/vu-block,path=disk.img` results in a working vhost-user block device. TEST=`crosvm devices --block vhost=0000:00:10.0,path=disk.img` results in a working VVU block device. TEST=regular virtio block device is usable as jailed root device. Change-Id: Ide62adbf81390eb39cd10f3d2880e2c065982d05 Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3765000 Reviewed-by: Daniel Verkamp <dverkamp@chromium.org> Commit-Queue: Alexandre Courbot <acourbot@chromium.org> Tested-by: Alexandre Courbot <acourbot@chromium.org> Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org> |
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Policy files for crosvm
This folder holds the seccomp policies for crosvm devices, organized by architecture.
Each crosvm device can run within its owned jailed process. A jailed process is only able to perform the system calls specified in the seccomp policy file the jail has been created with, which improves security as a rogue process cannot perform any system call it wants.
Each device can run from different contexts, which require a different set of authorized system calls. This file explains how the policy files are named in order to allow these various scenario.
Naming conventions
Since Minijail only allows for one level of policy inclusion, we need to be a little bit creative in order to minimize policy duplication.
common_device.policycontains a set of syscalls that are common to all devices, and is never loaded directly - only included from other policy files.foo.policycontains the set of syscalls that devicefoois susceptible to use, regardless of the underlying virtio transport. This policy is also never loaded directly.foo_device.policyis the policy that is loaded when devicefoois used as an in-VMM (i.e. regular virtio) device. It will generally simply includecommon_device.policyas well asfoo.policy.
When using vhost-user, the virtio protocol needs to be sent over a different medium, e.g. a Unix socket. Supporting this transport requires some extra system calls after the device is jailed, and thus dedicated policies:
vhost_user.policycontains the set of syscalls required by the regular (i.e. socket-based) vhost-user listener. It is never loaded directly.vvu.policycontains the set of syscalls required by the VFIO-based vhost-user (aka Virtio-Vhost-User) listener. It is also never loaded directly.foo_device_vhost_user.policyis the policy that is loaded when devicefoois used as a regular vhost-user device. It will generally includecommon_device.policy,vhost_user.policyandfoo.policy.foo_device_vvu.policyis the policy that is loaded when devicefoois used as a VVU device. It will generally includecommon_device.policy,vvu.policyandfoo.policy.