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When unpacking a SquashFS containing security.selinux xattrs, the AppArmor archive profile blocks access to writing these to the FS which crashes unsquashfs (but not tar).

Errors seen:

  • unsquashfs: FATAL ERROR: write_xattr: failed to write xattr security.selinux for file squashfs-root/etc/selinux/targeted/contexts/files/file_contexts because Operation not permitted
  • AA denials: apparmor="DENIED" operation="capable" class="cap" profile="incus_archive-cf1435b8-7543-419a-87a1-f656442c6e2f" pid=928 comm="unsquashfs" capability=21 capname="sys_admin" (similar for tar)

I'm not sure my changes are the correct solution for this behavior. I can think of several more:

  • Use the -xattrs-exclude ^security. to narrow down xattr exclusion (but only works for unsquashfs v4.6+)
  • Ignore errors that look like FATAL ERROR: write_xattr: failed to write xattr security. along with char/block device errors (but unsure whether the rest of the archive would be extracted)
  • Add sys_admin capability to archive AA profile to allow writing of security.* xattrs (this gives a lot of permissions but it is just a humble unpacking process after all)

Also, tar is similarly blocked by AA from writing these xattrs, but it fails with only an AA denial in syslog and a zero exit code, more or less silently stripping away the xattrs it cannot write. Perhaps it should also explicitly exclude security.* xattrs from unpacking? Or benefit from the addition of cap_sys_admin to the archive AA profile?

If some xattrs are to be excluded, that should probably be reflected in the documentation.

When unpacking a SquashFS containing `security.selinux` xattrs, the
AppArmor archive profile blocks access to writing these to the FS which
crashes unsquashfs (but not tar).

Signed-off-by: Gabriel Totev <gabriel.totev@zetier.com>
@zgttotev zgttotev requested a review from stgraber as a code owner April 14, 2025 22:36
@stgraber stgraber merged commit e058e29 into lxc:main Apr 15, 2025
38 checks passed
@zgttotev zgttotev deleted the archive-xattrs branch April 15, 2025 14:37
tmeijn pushed a commit to tmeijn/dotfiles that referenced this pull request May 10, 2025
This MR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [lxc/incus](https://github.com/lxc/incus) | minor | `v6.11.0` -> `v6.12.0` |

MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot).

**Proposed changes to behavior should be submitted there as MRs.**

---

### Release Notes

<details>
<summary>lxc/incus (lxc/incus)</summary>

### [`v6.12.0`](https://github.com/lxc/incus/releases/tag/v6.12.0): Incus 6.12

[Compare Source](lxc/incus@v6.11.0...v6.12.0)

### Announcement

https://discuss.linuxcontainers.org/t/incus-6-12-has-been-released/23556

#### What's Changed

-   doc: Fix missing OCI section by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1855
-   doc: Fix config option reference on LINSTOR driver by [@&#8203;luissimas](https://github.com/luissimas) in lxc/incus#1857
-   Add support for server-side filtering by instance name by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1856
-   incusd/instance/lxc: Fix max gid when in a privileged container by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1859
-   Fix some static analysis nits by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1860
-   README: Fix typo by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1861
-   Docs: correct restriction on `path` option by [@&#8203;gwenya](https://github.com/gwenya) in lxc/incus#1862
-   lxd-to-incus: Fix typo in trigger by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1865
-   incusd/instance/edk2: Limit test to UEFI architectures by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1866
-   doc: Tweak ACME documentation by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1868
-   instances/drivers/qemu: update user parameter for QEMU v9.1+ by [@&#8203;dnegreira](https://github.com/dnegreira) in lxc/incus#1871
-   OCI improvements by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1873
-   Support server-side filtering by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1872
-   Enable filtering with the `all-projects` flag when listing images by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1874
-   Improve migration by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1878
-   incusd/storage: Add missing forwarding on snapshot list by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1882
-   incusd/instance/common: Fix concurrent restarts by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1884
-   Fix all static analysis in client/, shared/ and cmd/incus/ by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1883
-   generate-database: Fix documentation for `ignore` by [@&#8203;breml](https://github.com/breml) in lxc/incus#1885
-   incusd/response: Remove redundant line break in error by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1886
-   RFC 3442 compliance in forknet dhcp client by [@&#8203;gwenya](https://github.com/gwenya) in lxc/incus#1887
-   incus-agent: Retry mounts to avoid kernel races by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1888
-   Address sets for nftables and OVN by [@&#8203;irhndt](https://github.com/irhndt) in lxc/incus#1728
-   incusd/operations: Fix WaitGet on op failure by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1894
-   Update list of compresors by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1892
-   Add snapshot pre-fetching support by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1891
-   incusd/instance/lxc: Use pre-existing PATH when not overridden by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1895
-   incusd/acme: Include CA in generate certificate by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1897
-   Usability improvements to incus-migrate by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1898
-   client/incus: Fix non-constant format strings by [@&#8203;c4t3l](https://github.com/c4t3l) in lxc/incus#1899
-   docs: mDNS setup for cluster HA by [@&#8203;MOZGIII](https://github.com/MOZGIII) in lxc/incus#1896
-   Support filtering storage volumes by a single keyword by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1915
-   incusd/instance/qemu: Clean leftover sockets on startup by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1916
-   incusd: Implement Incus OS API forwarding by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1918
-   Add generated documentation for network bridge by [@&#8203;NathanChase22](https://github.com/NathanChase22) in lxc/incus#1920
-   doc: Use `$USER` instead of YOUR-USERNAME by [@&#8203;bjackman](https://github.com/bjackman) in lxc/incus#1922
-   doc: Ignore link that's blocking Azure by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1924
-   Storage bugfixes by [@&#8203;bensmrs](https://github.com/bensmrs) in lxc/incus#1923
-   incusd/patches: Refresh OpenFGA model for address sets by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1925
-   Add generated documentation for network forwards by [@&#8203;tonyn10](https://github.com/tonyn10) in lxc/incus#1926
-   Add support for configurable logging targets  by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1903
-   Port tpm device documentation to gendoc by [@&#8203;saahirN](https://github.com/saahirN) in lxc/incus#1929
-   Allow basic connectivity under nftables by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1930
-   incusd/storage/zfs: Make CacheVolumeSnapshots failures non-fatal by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1931
-   incusd/instance/lxc: Restrict unprivileged ping to recent kernels by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1934
-   Implement SNAT as part of network forwards by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1935
-   incusd/apparmor/lxc: Allow write access to /proc/sys/user by [@&#8203;zgttotev](https://github.com/zgttotev) in lxc/incus#1937
-   incusd/instance/lxc: Defer calls to the scheduler by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1938
-   shared/archive: Prevent xattr errors from crashing unsquashfs by [@&#8203;zgttotev](https://github.com/zgttotev) in lxc/incus#1939
-   Extend use of ZFS pre-caching by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1941
-   Add common aliases for add/create remove/delete/rm in the CLI by [@&#8203;joecwilson](https://github.com/joecwilson) in lxc/incus#1943
-   feat: support access_token query parameter as JWT fallback by [@&#8203;irtaza9](https://github.com/irtaza9) in lxc/incus#1940
-   Memory hotplug support for VMs by [@&#8203;presztak](https://github.com/presztak) in lxc/incus#1945
-   incusd: Remove old routing logic by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1947
-   Fix refresh migrations in cluster and speed up ZFS startup by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1946
-   incusd/devices: Don't require a serial number for USB hotplug by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1949
-   Move tls testing functions to tlstest by [@&#8203;nanjj](https://github.com/nanjj) in lxc/incus#1948
-   Remove Rican7/retry dependency by [@&#8203;nanjj](https://github.com/nanjj) in lxc/incus#1952
-   Port `proxy` device documentation to `gendoc` by [@&#8203;Abdomash](https://github.com/Abdomash) in lxc/incus#1953
-   Port gpu device documentation to gendoc by [@&#8203;kmxtn](https://github.com/kmxtn) in lxc/incus#1954
-   Port nic device documentation to gendoc by [@&#8203;rahafjrw](https://github.com/rahafjrw) in lxc/incus#1956
-   Remove arping dependency by [@&#8203;ahmetfturhan](https://github.com/ahmetfturhan) in lxc/incus#1958
-   Remove gocapability dependency by [@&#8203;nanjj](https://github.com/nanjj) in lxc/incus#1957
-   Infiniband Device Documentation Ported to GenDoc by [@&#8203;AbhinavTiruvee](https://github.com/AbhinavTiruvee) in lxc/incus#1962
-   Replace rebfig/cron/v3 with adhocore/gronx by [@&#8203;nanjj](https://github.com/nanjj) in lxc/incus#1959
-   Update help of `incus storage list` by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1968
-   shared/api/scriptlet: Add yaml struct tags by [@&#8203;breml](https://github.com/breml) in lxc/incus#1973
-   incusd/storage/migration: Check instance size during migration by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1971
-   Logfile for forknet dhcp by [@&#8203;gwenya](https://github.com/gwenya) in lxc/incus#1976
-   Add dhcp static routes via 0.0.0.0 with link scope in forknet by [@&#8203;gwenya](https://github.com/gwenya) in lxc/incus#1977
-   incusd/device/disk: Fix registration of custom volumes by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1980
-   Add server side filtering for `incus profile list` by [@&#8203;Abdomash](https://github.com/Abdomash) in lxc/incus#1982
-   Fix reference passing when yaml unmarshal by [@&#8203;nanjj](https://github.com/nanjj) in lxc/incus#1984
-   Various fixes by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1983
-   scriptlet: Return proper error by [@&#8203;breml](https://github.com/breml) in lxc/incus#1986
-   incusd/instance: Also consider local CPU flags by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1987
-   Cap maximum VM memory to match host memory total by [@&#8203;stgraber](https://github.com/stgraber) in lxc/incus#1988

#### New Contributors

-   [@&#8203;dnegreira](https://github.com/dnegreira) made their first contribution in lxc/incus#1871
-   [@&#8203;c4t3l](https://github.com/c4t3l) made their first contribution in lxc/incus#1899
-   [@&#8203;MOZGIII](https://github.com/MOZGIII) made their first contribution in lxc/incus#1896
-   [@&#8203;NathanChase22](https://github.com/NathanChase22) made their first contribution in lxc/incus#1920
-   [@&#8203;bjackman](https://github.com/bjackman) made their first contribution in lxc/incus#1922
-   [@&#8203;tonyn10](https://github.com/tonyn10) made their first contribution in lxc/incus#1926
-   [@&#8203;saahirN](https://github.com/saahirN) made their first contribution in lxc/incus#1929
-   [@&#8203;zgttotev](https://github.com/zgttotev) made their first contribution in lxc/incus#1937
-   [@&#8203;joecwilson](https://github.com/joecwilson) made their first contribution in lxc/incus#1943
-   [@&#8203;irtaza9](https://github.com/irtaza9) made their first contribution in lxc/incus#1940
-   [@&#8203;Abdomash](https://github.com/Abdomash) made their first contribution in lxc/incus#1953
-   [@&#8203;kmxtn](https://github.com/kmxtn) made their first contribution in lxc/incus#1954
-   [@&#8203;rahafjrw](https://github.com/rahafjrw) made their first contribution in lxc/incus#1956
-   [@&#8203;ahmetfturhan](https://github.com/ahmetfturhan) made their first contribution in lxc/incus#1958
-   [@&#8203;AbhinavTiruvee](https://github.com/AbhinavTiruvee) made their first contribution in lxc/incus#1962

**Full Changelog**: lxc/incus@v6.11.0...v6.12.0

</details>

---

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