xattrs are revealing some unfortunate brittleness in real world
derivations that are getting -EINVAL errors while executing their test
code.
The reason for this is that Linux checks [1] UID delegations for xattrs
writes.
In the Lix sandbox, except if you enabled a uid-range feature, you have
exactly 3 UIDs: root, nixbld and nobody.
If your test code makes use of UIDs which have not been delegated, you
will receive an EINVAL on your operation. Test code is not resilient
with respect to the number of available UIDs in their namespace.
To avoid further issues for end users who are running into spurious
derivation build failures, we forbid xattrs again for now.
For more information about the plans, please consult or chime in [2].
Fixes#1105. Reopens#838. Fixes#1103.
[1]: https://elixir.bootlin.com/linux/v6.18.6/source/fs/posix_acl.c#L257
[2]: https://zulip.lix.systems/#narrow/channel/9-Store/topic/disablement.20of.20xattrs/with/5295
Change-Id: I864066b34cd8319d2271fac1b179cb4f950d836e
Signed-off-by: Raito Bezarius <raito@lix.systems>
See: cl/4840
When importing Python modules, we include `functional2` in the module
path, like this:
from functional2.testlib.fixtures.env import ManagedEnv
This means that python expects to see a file like
`functional2/testlib/fixtures/env.py`. We run `pytest` from `tests/` in
the `justfile` and have `tests/functional2/__init__.py` so `pytest` in
`meson` is able to find these imports.
However, language servers generally consider the `pyproject.toml` to be
the project root, so (e.g.) `pyright` is unable to follow any of the
`functional2` imports, leading to lots of spurious errors.
In cl/4840 I moved `tests/functional2/pyproject.toml` to
`tests/pyproject.toml`, which worked but was considered aesthetically
unappealing.
This diff is much larger but it's a more elegant solution.
Change-Id: I2983c7b87f88f59a4e3521451a9f5acd6a6a6964
Fixes#838.
xattrs were historically disabled in 2017, since then, NFS v4.2 gained
support for xattrs and almost all filesystems support xattrs. In
addition, moving the build directory to a xattrs-supporting filesystem
is always an option. Programs may exploit xattrs (including ACLs) during
their build process and testing phase, to better serve these programs,
we will remove this limitation.
Lix will use POSIX ACLs for its UNIX domain sockets in the future and be
one of these programs which will run tests making use of xattrs, while
not writing any xattrs in the derivation outputs themselves.
xattrs are still scrubbed from derivation outputs so it is not possible
to obtain an advantage by writing a security-related xattr to a well
chosen file.
Tests were added to test these scenarios on Linux. Darwin is carefully
excluded because of #1008 and #1090, solving that is welcome. In the
meantime, they are marked xfail.
Change-Id: Ia3255eeb8442e83db4f10dcb5a51cbc368a2550d
Signed-off-by: Raito Bezarius <raito@lix.systems>
Raito Bezarius