AppArmor causing application inside LXD container to crash

I’m trying to get the application signal-desktop running inside an LXD container.
Graphics-wise I’m using wayland, and pass-through the wayland socket as proxy via bind-mount.

signal-desktop is an electron app, apparently based on some chromium related code.

The app crashes inside the LXD container with (wayland debug output enabled):

[..]
[2073146.492] wl_display@1.delete_id(36)
[2073146.512] wl_display@1.error(wl_display@1, 1, "invalid arguments for wl_shm@4.create_pool")
[620:1127/100825.302174:ERROR:wayland_event_watcher.cc(39)] libwayland: wl_display@1: error 1: invalid arguments for wl_shm@4.create_pool

Trace/breakpoint trap (core dumped)

On the hypervisor I see the following messages:

[610779.738989] audit: type=1400 audit(1701117927.016:405): apparmor="DENIED" operation="file_receive" class="file" profile="lxd_forkproxy-waylandsocket_chat_</var/lib/lxd>" name="/dev/shm/.org.chromium.Chromium.Nkdyfp" pid=3587566 comm="lxd" requested_mask="w" denied_mask="w" fsuid=1000 ouid=17701000
[610779.761540] traps: signal-desktop[3706370] trap int3 ip:562a702dee1d sp:7ffc3f0ce090 error:0 in signal-desktop[562a6f407000+785e000]

So, it seems apparmor causes the application to crash, as it denies it access to some shared memory space.

Normally, I’d assume I “just” need to allow the application access to /dev/shm/.org.chromium.Chromium.*.

However the “application” apparmor is denying access to does /not/ appear to be signal-desktop but lxd - at least that’s how I interpret the dmesg-messages on the hypervisor.
I wouldn’t want to just enable this for all and everything, but only this very container - or even better - only this application (signal-desktop) inside this particular container.

How do I get signal-desktop running inside an LXD container using wayland, without degrading security for other applications / containers?

Hi @wc-ubuntu,

Can you please post the output of lxc info, as well as the configuration of your container (lxc config show <container> --expanded) and any manual steps you have taken to install and run signal-desktop.

Thanks.

1 Like

Installation of signal-desktop by adding the apt source deb [arch=amd64 signed-by=/usr/share/keyrings/signal-desktop-keyring.gpg] https://updates.signal.org/desktop/apt xenial main and installing package signal-desktop.

LXC container was Debian bookworm and is now upgraded to Debian trixie - no difference.

Within the container I symlink /dom0/socks/wayland-0/run/user/1000/wayland-0

signal-desktop is being launched by: signal-desktop --enable-features=UseOzonePlatform --ozone-platform-hint=wayland

lxc config show chat --expanded:

architecture: x86_64
config:
  boot.autostart: "false"
  image.architecture: amd64
  image.description: Debian buster amd64 (20190709_05:24)
  image.os: Debian
  image.release: buster
  image.serial: "20190709_05:24"
  security.idmap.base: "17700000"
  security.idmap.isolated: "true"
  security.idmap.size: "100000"
  security.nesting: "true"
  volatile.base_image: 917dbf3684690e16fb6f5f0b087d411bfe391a45044322c6d95b8eb72234b75a
  volatile.eth0.host_name: vethd6969010
  volatile.eth0.hwaddr: 00:16:3e:6b:73:0b
  volatile.idmap.base: "17700000"
  volatile.idmap.current: '[{"Isuid":true,"Isgid":false,"Hostid":17700000,"Nsid":0,"Maprange":100000},{"Isuid":false,"Isgid":true,"Hostid":17700000,"Nsid":0,"Maprange":100000}]'
  volatile.idmap.next: '[{"Isuid":true,"Isgid":false,"Hostid":17700000,"Nsid":0,"Maprange":100000},{"Isuid":false,"Isgid":true,"Hostid":17700000,"Nsid":0,"Maprange":100000}]'
  volatile.last_state.idmap: '[{"Isuid":true,"Isgid":false,"Hostid":17700000,"Nsid":0,"Maprange":100000},{"Isuid":false,"Isgid":true,"Hostid":17700000,"Nsid":0,"Maprange":100000}]'
  volatile.last_state.power: RUNNING
  volatile.uuid: 8be452f1-8e35-4a20-a974-0921a061f786
devices:
  eth0:
    name: eth0
    network: br-lxc
    type: nic
  mygpu:
    gid: "1000"
    type: gpu
    uid: "1000"
  root:
    path: /
    pool: thinpool
    type: disk
  waylandsocket:
    bind: container
    connect: unix:/run/user/1000/wayland-1
    gid: "1000"
    listen: unix:/dom0/socks/wayland-0
    mode: "0660"
    security.gid: "1000"
    security.uid: "1000"
    type: proxy
    uid: "1000"
ephemeral: false
profiles:
- default
stateful: false
description: ""

lxc info:

config:
  images.auto_update_cached: "false"
  images.auto_update_interval: "0"
api_extensions:
- storage_zfs_remove_snapshots
- container_host_shutdown_timeout
- container_stop_priority
- container_syscall_filtering
- auth_pki
- container_last_used_at
- etag
- patch
- usb_devices
- https_allowed_credentials
- image_compression_algorithm
- directory_manipulation
- container_cpu_time
- storage_zfs_use_refquota
- storage_lvm_mount_options
- network
- profile_usedby
- container_push
- container_exec_recording
- certificate_update
- container_exec_signal_handling
- gpu_devices
- container_image_properties
- migration_progress
- id_map
- network_firewall_filtering
- network_routes
- storage
- file_delete
- file_append
- network_dhcp_expiry
- storage_lvm_vg_rename
- storage_lvm_thinpool_rename
- network_vlan
- image_create_aliases
- container_stateless_copy
- container_only_migration
- storage_zfs_clone_copy
- unix_device_rename
- storage_lvm_use_thinpool
- storage_rsync_bwlimit
- network_vxlan_interface
- storage_btrfs_mount_options
- entity_description
- image_force_refresh
- storage_lvm_lv_resizing
- id_map_base
- file_symlinks
- container_push_target
- network_vlan_physical
- storage_images_delete
- container_edit_metadata
- container_snapshot_stateful_migration
- storage_driver_ceph
- storage_ceph_user_name
- resource_limits
- storage_volatile_initial_source
- storage_ceph_force_osd_reuse
- storage_block_filesystem_btrfs
- resources
- kernel_limits
- storage_api_volume_rename
- macaroon_authentication
- network_sriov
- console
- restrict_devlxd
- migration_pre_copy
- infiniband
- maas_network
- devlxd_events
- proxy
- network_dhcp_gateway
- file_get_symlink
- network_leases
- unix_device_hotplug
- storage_api_local_volume_handling
- operation_description
- clustering
- event_lifecycle
- storage_api_remote_volume_handling
- nvidia_runtime
- container_mount_propagation
- container_backup
- devlxd_images
- container_local_cross_pool_handling
- proxy_unix
- proxy_udp
- clustering_join
- proxy_tcp_udp_multi_port_handling
- network_state
- proxy_unix_dac_properties
- container_protection_delete
- unix_priv_drop
- pprof_http
- proxy_haproxy_protocol
- network_hwaddr
- proxy_nat
- network_nat_order
- container_full
- candid_authentication
- backup_compression
- candid_config
- nvidia_runtime_config
- storage_api_volume_snapshots
- storage_unmapped
- projects
- candid_config_key
- network_vxlan_ttl
- container_incremental_copy
- usb_optional_vendorid
- snapshot_scheduling
- snapshot_schedule_aliases
- container_copy_project
- clustering_server_address
- clustering_image_replication
- container_protection_shift
- snapshot_expiry
- container_backup_override_pool
- snapshot_expiry_creation
- network_leases_location
- resources_cpu_socket
- resources_gpu
- resources_numa
- kernel_features
- id_map_current
- event_location
- storage_api_remote_volume_snapshots
- network_nat_address
- container_nic_routes
- rbac
- cluster_internal_copy
- seccomp_notify
- lxc_features
- container_nic_ipvlan
- network_vlan_sriov
- storage_cephfs
- container_nic_ipfilter
- resources_v2
- container_exec_user_group_cwd
- container_syscall_intercept
- container_disk_shift
- storage_shifted
- resources_infiniband
- daemon_storage
- instances
- image_types
- resources_disk_sata
- clustering_roles
- images_expiry
- resources_network_firmware
- backup_compression_algorithm
- ceph_data_pool_name
- container_syscall_intercept_mount
- compression_squashfs
- container_raw_mount
- container_nic_routed
- container_syscall_intercept_mount_fuse
- container_disk_ceph
- virtual-machines
- image_profiles
- clustering_architecture
- resources_disk_id
- storage_lvm_stripes
- vm_boot_priority
- unix_hotplug_devices
- api_filtering
- instance_nic_network
- clustering_sizing
- firewall_driver
- projects_limits
- container_syscall_intercept_hugetlbfs
- limits_hugepages
- container_nic_routed_gateway
- projects_restrictions
- custom_volume_snapshot_expiry
- volume_snapshot_scheduling
- trust_ca_certificates
- snapshot_disk_usage
- clustering_edit_roles
- container_nic_routed_host_address
- container_nic_ipvlan_gateway
- resources_usb_pci
- resources_cpu_threads_numa
- resources_cpu_core_die
- api_os
- container_nic_routed_host_table
- container_nic_ipvlan_host_table
- container_nic_ipvlan_mode
- resources_system
- images_push_relay
- network_dns_search
- container_nic_routed_limits
- instance_nic_bridged_vlan
- network_state_bond_bridge
- usedby_consistency
- custom_block_volumes
- clustering_failure_domains
- resources_gpu_mdev
- console_vga_type
- projects_limits_disk
- network_type_macvlan
- network_type_sriov
- container_syscall_intercept_bpf_devices
- network_type_ovn
- projects_networks
- projects_networks_restricted_uplinks
- custom_volume_backup
- backup_override_name
- storage_rsync_compression
- network_type_physical
- network_ovn_external_subnets
- network_ovn_nat
- network_ovn_external_routes_remove
- tpm_device_type
- storage_zfs_clone_copy_rebase
- gpu_mdev
- resources_pci_iommu
- resources_network_usb
- resources_disk_address
- network_physical_ovn_ingress_mode
- network_ovn_dhcp
- network_physical_routes_anycast
- projects_limits_instances
- network_state_vlan
- instance_nic_bridged_port_isolation
- instance_bulk_state_change
- network_gvrp
- instance_pool_move
- gpu_sriov
- pci_device_type
- storage_volume_state
- network_acl
- migration_stateful
- disk_state_quota
- storage_ceph_features
- projects_compression
- projects_images_remote_cache_expiry
- certificate_project
- network_ovn_acl
- projects_images_auto_update
- projects_restricted_cluster_target
- images_default_architecture
- network_ovn_acl_defaults
- gpu_mig
- project_usage
- network_bridge_acl
- warnings
- projects_restricted_backups_and_snapshots
- clustering_join_token
- clustering_description
- server_trusted_proxy
- clustering_update_cert
- storage_api_project
- server_instance_driver_operational
- server_supported_storage_drivers
- event_lifecycle_requestor_address
- resources_gpu_usb
- clustering_evacuation
- network_ovn_nat_address
- network_bgp
- network_forward
- custom_volume_refresh
- network_counters_errors_dropped
- metrics
- image_source_project
- clustering_config
- network_peer
- linux_sysctl
- network_dns
- ovn_nic_acceleration
- certificate_self_renewal
- instance_project_move
- storage_volume_project_move
- cloud_init
- network_dns_nat
- database_leader
- instance_all_projects
- clustering_groups
- ceph_rbd_du
- instance_get_full
- qemu_metrics
- gpu_mig_uuid
- event_project
- clustering_evacuation_live
- instance_allow_inconsistent_copy
- network_state_ovn
- storage_volume_api_filtering
- image_restrictions
- storage_zfs_export
- network_dns_records
- storage_zfs_reserve_space
- network_acl_log
- storage_zfs_blocksize
- metrics_cpu_seconds
- instance_snapshot_never
- certificate_token
- instance_nic_routed_neighbor_probe
- event_hub
- agent_nic_config
- projects_restricted_intercept
- metrics_authentication
- images_target_project
- cluster_migration_inconsistent_copy
- cluster_ovn_chassis
- container_syscall_intercept_sched_setscheduler
- storage_lvm_thinpool_metadata_size
- storage_volume_state_total
- instance_file_head
- resources_pci_vpd
- qemu_raw_conf
- storage_cephfs_fscache
- vsock_api
- storage_volumes_all_projects
- projects_networks_restricted_access
- cluster_join_token_expiry
- remote_token_expiry
- init_preseed
- cpu_hotplug
api_status: stable
api_version: "1.0"
auth: trusted
public: false
auth_methods:
- tls
environment:
  addresses: []
  architectures:
  - x86_64
  - i686
  certificate: |
    -----BEGIN CERTIFICATE-----
    -----END CERTIFICATE-----
  certificate_fingerprint: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  driver: lxc | qemu
  driver_version: 5.0.3 | 8.1.2
  firewall: nftables
  kernel: Linux
  kernel_architecture: x86_64
  kernel_features:
    idmapped_mounts: "true"
    netnsid_getifaddrs: "true"
    seccomp_listener: "true"
    seccomp_listener_continue: "true"
    shiftfs: "false"
    uevent_injection: "true"
    unpriv_fscaps: "true"
  kernel_version: 6.5.0-4-amd64
  lxc_features:
    cgroup2: "true"
    core_scheduling: "true"
    devpts_fd: "true"
    idmapped_mounts_v2: "true"
    mount_injection_file: "true"
    network_gateway_device_route: "true"
    network_ipvlan: "true"
    network_l2proxy: "true"
    network_phys_macvlan_mtu: "true"
    network_veth_router: "true"
    pidfd: "true"
    seccomp_allow_deny_syntax: "true"
    seccomp_notify: "true"
    seccomp_proxy_send_notify_fd: "true"
  os_name: Debian GNU/Linux
  os_version: ""
  project: default
  server: lxd
  server_clustered: false
  server_event_mode: full-mesh
  server_name: thar
  server_pid: 2527
  server_version: 5.0.2
  storage: lvm
  storage_version: 2.03.16(2) (2022-05-18) / 1.02.185 (2022-05-18) / 4.48.0
  storage_supported_drivers:
  - name: btrfs
    version: 6.3.2
    remote: false
  - name: dir
    version: "1"
    remote: false
  - name: lvm
    version: 2.03.16(2) (2022-05-18) / 1.02.185 (2022-05-18) / 4.48.0
    remote: false

I also couldn’t get this to work for wayland. But I did get it to work with X11 using this profile https://discuss.linuxcontainers.org/t/incus-lxd-profile-for-gui-apps-wayland-x11-and-pulseaudio/18295.

I appreciate the alternative, but my main objective is to get it working with wayland and also to understand how LXD and apparmor work together (or don’t)

When you add a proxy device to the container (waylandsocket) there is a new apparmor profile created under /var/snap/lxd/common/lxd/security/apparmor/profiles (when LXD is installed through the snap, otherwise different dir). Looks like this profile is blocking access to /dev/shm/.org.chromium.Chromium.Nkdyfp through the proxy device.

It doesn’t look to be LXD who is trying to access something here, instead some application inside the container fails reading a file which gets blocked by apparmor on the hypervisor.

You can try tweaking the apparmor settings using https://documentation.ubuntu.com/lxd/en/latest/reference/instance_options/#instance-raw:raw.apparmor.
Please follow up here with any findings or if LXD isn’t doing what it is supposed to do.