This adds a small, socket-activated Varlink daemon that can delegate UID
ranges for user namespaces to clients asking for it.
The primary call is AllocateUserRange() where the user passes in an
uninitialized userns fd, which is then set up.
There are other calls that allow assigning a mount fd to a userns
allocated that way, to set up permissions for a cgroup subtree, and to
allocate a veth for such a user namespace.
Since the UID assignments are supposed to be transitive, i.e. not
permanent, care is taken to ensure that users cannot create inodes owned
by these UIDs, so that persistancy cannot be acquired. This is
implemented via a BPF-LSM module that ensures that any member of a
userns allocated that way cannot create files unless the mount it
operates on is owned by the userns itself, or is explicitly
allowelisted.
BPF LSM program with contributions from Alexei Starovoitov.
This is just good style. In this particular case, if the argument is incorrect and
the function is not tested with $NOTIFY_SOCKET set, the user could not get the
proper error until running for real.
Also, remove mention of systemd. The protocol is fully generic on purpose.
F40 will be out soon, so we can update the man page already. The example should
already work.
The cloud link was dropped in fd571c9df0, so
drop the unused variable too.
Unfortunately, sd-bus-vtable.h, sd-journal.h, and sd-id128.h
have variadic macro and inline initialization of sub-object, these are
not supported in C90. So, we need to silence some errors.
I think the example should reflect the full set of lifecycle messages,
including STOPPING=1, which tells the service manager that the service
is already terminating. This is useful for reporting this information
back to the user and to suppress repeated shutdown requests.
It's not as important as the READY=1 and RELOADING=1 messages, since we
actively wait for those from the service message if the right Type= is
set. But it's still very valuable information, easy to do, and completes
the state engine.
stale HibernateLocation EFI variable
Currently, if the HibernateLocation EFI variable exists,
but we failed to resume from it, the boot carries on
without clearing the stale variable. Therefore, the subsequent
boots would still be waiting for the device timeout,
unless the variable is purged manually.
There's no point to keep trying to resume after a successful
switch-root, because the hibernation image state
would have been invalidated by then. OTOH, we don't
want to clear the variable prematurely either,
i.e. in initrd, since if the resume device is the same
as root one, the boot won't succeed and the user might
be able to try resuming again. So, let's introduce a
unit that only runs after switch-root and clears the var.
Fixes#32021
