This is an octal number. We used the 0 prefix in some places inconsistently.
The kernel always interprets in base-8, so this has no effect, but I think
it's nicer to use the 0 to remind the reader that this is not a decimal number.
When generators are executed during early boot, /tmp might not be available
yet. This causes problems with bash, because here-docs don't work. Even
non-shell code can often assume that /tmp is available. This limitation is
known to trip up people, and when the code is tested on a "normal" system,
everything works.
We can solve this nicely, and get another small benefit, by making most of the
file system read-only and "punching holes" for some dirs that should be
writable. The generator code runs with full privileges and can do anything it
wants by writing appropriate systemd units, so it doesn't make much sense to do
any significant sandboxing around generators. But making root read-only is nice
because it can catch stupid mistakes where the generator tries to write to a
wrong path or something like that. We effectively also get a "private /tmp" for
the generators, which protects them against existing files in /tmp.
The path does the following:
when executing generators, we fork, and the child unshares root and makes
it recursively read-only, with the exception of /sys and /run. Error handling
is permissive — if some of this setup fails, we're in the same state as
before the patch.
Fixes#24430.
If the page size of a swap space doesn't match the page size of the
currently running kernel, swapon will fail. Let's instruct it to
reinitialize the swap space instead.
Reloading is a heavy-weight operation, and currently it is not
possible to stop an orchestrator from spamming reload requests.
Add configuration options to allow rate-limiting.
Reloading is a heavy-weight operation, and currently it is not
possible to figure out who/what requested it, even at debug level
logging.
Check the sender of the D-Bus message and print it out at info level.
RUN_WITH_UMASK was initially conceived for spawning externals progs with the
umask set. But nowadays we use it various syscalls and stuff that doesn't "run"
anything, so the "RUN_" prefix has outlived its usefulness.
The `frozen` state can be `0` while the processes are indeed frozen (see
last commit). Therefore do not respect cgroup.events when checking
whether thawing is necessary.
Sometimes a freeze operation can hang due to the presence of kernel
threads inside the unit cgroup (e.g. QEMU-KVM). This ensures that the
ThawUnit operation invoked by systemd-sleep at wakeup always thaws the
unit.
Inspired by #25664: let's check explicitly for NULL everywhere we do one
of those getXYZcon() calls.
We usually turn this into EOPNOTSUPP, as when selinux is off (which is
supposed to be the only case this can happen according to selinux docs)
we otherwise return EOPNOTSUPP in that case.
Note that in most cases we have an explicit mac_selinux_use() call
beforehand, hence this should mostly not be triggerable codepaths.
In order to support pivot_root() we need to move mount propagation
changes after the pivot_root(). While MS_MOVE requires the source mount
to not be a shared mount pivot_root() also requires the target mount to
not be a shared mount. This guarantees that pivot_root() doesn't leak
any mounts.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Trying to disable a unit with no install info is mostly useless, so
adding a warning like we do for enable (with the new dbus method
'DisableUnitFilesWithFlagsAndInstallInfo()'). Note that it would
still find and remove symlinks to the unit in /etc, regardless of
whether it has install info or not, just like before. And if there are
actually files to remove, we suppress the warning.
Fixes#17689
When booting with debug logs, we print:
Setting '/proc/sys/fs/file-max' to '9223372036854775807
'
Setting '/proc/sys/fs/nr_open' to '2147483640
'
Couldn't write fs.nr_open as 2147483640, halving it.
Setting '/proc/sys/fs/nr_open' to '1073741816
'
Successfully bumped fs.nr_open to 1073741816
The strange formatting is because we explicitly appended a newline in those two
places. It seems that the kernel doesn't care. In fact, we have a few dozen other
writes to sysctl where we don't append a newline. So let's just drop those here
too, to make the code a bit simpler and avoid strange output in the logs.
Curently, these two flags were implied by dissect_loop_device(), but
that's not right, because this means systemd-gpt-auto-generator will
dissect the root block device with these flags set and that's not
desirable: the generator should not cause the partition devices to be
created (we don't intend to use them right-away after all, but expect
udev to find/probe them first, and then mount them though .mount units).
And there's no point in opening the partition devices, since we do not
intend to mount them via fds either.
Hence, rework this: instead of implying the flags, specify them
explicitly.
While we are at it, let's also rename the flags to make them more
descriptive:
DISSECT_IMAGE_MANAGE_PARTITION_DEVICES becomes
DISSECT_IMAGE_ADD_PARTITION_DEVICES, since that's really all this does:
add the partition devices via BLKPG.
DISSECT_IMAGE_OPEN_PARTITION_DEVICES becomes
DISSECT_IMAGE_PIN_PARTITION_DEVICES, since we not only open the devices,
but keep the devices open continously (i.e. we "pin" them).
Also, drop the DISSECT_IMAGE_BLOCK_DEVICE combination flag, since it is
misleading, i.e. it suggests it was appropriate to specify on all
dissected blocking devices, but that's precisely not the case, see the
systemd-gpt-auto-generator case. My guess is that the confusion around
this was actually the cause for this bug we are addressing here.
Fixes: #25528
Currently, services use mount_move_root() in order to setup the root
directory of services using a mount namespace. This relies on MS_MOVE
and chroot(). However, this has serious drawbacks even for relatively
simple mount propagation scenarios.
What systemd currently does is roughly equivalent to the following shell
code:
unshare --mount --propagation=shared
cd /
mount --make-rslave /
mkdir /new-root
mount --rbind / /new-root
cd /new-root
mount --move /new-root /
chroot .
This looks simple enough but has the consequence that two separate mount
trees exist for the lifetime of the service. The first one was created
when the mount namespace was created, and the second one when a new
mount for the rootfs was created. The first mount tree sticks around as
a shadow mount tree. Both mount trees are dependent mounts with the host
rootfs as their dominating mount.
Now, when mount propagation is triggered by the host by e.g.,
mount --bind /opt /mnt
it means that two propagation events are generated. I'm skipping over
the exact kernel details as they aren't that important. The gist is that
for every propagation event that is generated a second one is generated
for the shadow mount tree. In other words, the kernel creates two copies
for each mount that is propagated instead of one.
This isn't necessary. We can simply change the sequence above to:
unshare --mount --propagation=shared
cd /
mount --make-rslave /
mkdir /new-root
# stash fd to old rootfs
# stash fd to new rootfs
mount --rbind / /new-root
mkdir /new-root
cd /new-root
pivot_root . .
# new root is tucked under old root
# chdir into old rootfs via stashed fd
umount -l /old-root
The pivot_root allows us to get rid of the old mount tree that was
created when the mount namespace was created. So after this sequence
only one mount tree is alive. Plus, it's safer and nicer. Moving mounts
isn't pleasnt.
This patch doesn't convert nspawn yet as the requirements are more
tricky given that it wants to preserve the rootfs as a shared mount
which goes against pivot_root() requirements.
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
The compiler should recognize that these are constant expressions, but
let's better make this explicit, so that the linker can safely share the
initializations all over the place.
If we call raise(), we lose the information from the original signal.
If we use rt_sigqueueinfo(), the original siginfo gets reused which
is helpful when debugging crashes.
Rather than passing seeds up to userspace via EFI variables, pass seeds
directly to the kernel's EFI stub loader, via LINUX_EFI_RANDOM_SEED_TABLE_GUID.
EFI variables can potentially leak and suffer from forward secrecy
issues, and processing these with userspace means that they are
initialized much too late in boot to be useful. In contrast,
LINUX_EFI_RANDOM_SEED_TABLE_GUID uses EFI configuration tables, and so
is hidden from userspace entirely, and is parsed extremely early on by
the kernel, so that every single call to get_random_bytes() by the
kernel is seeded.
In order to do this properly, we use a bit more robust hashing scheme,
and make sure that each input is properly memzeroed out after use. The
scheme is:
key = HASH(LABEL || sizeof(input1) || input1 || ... || sizeof(inputN) || inputN)
new_disk_seed = HASH(key || 0)
seed_for_linux = HASH(key || 1)
The various inputs are:
- LINUX_EFI_RANDOM_SEED_TABLE_GUID from prior bootloaders
- 256 bits of seed from EFI's RNG
- The (immutable) system token, from its EFI variable
- The prior on-disk seed
- The UEFI monotonic counter
- A timestamp
This also adjusts the secure boot semantics, so that the operation is
only aborted if it's not possible to get random bytes from EFI's RNG or
a prior boot stage. With the proper hashing scheme, this should make
boot seeds safe even on secure boot.
There is currently a bug in Linux's EFI stub in which if the EFI stub
manages to generate random bytes on its own using EFI's RNG, it will
ignore what the bootloader passes. That's annoying, but it means that
either way, via systemd-boot or via EFI stub's mechanism, the RNG *does*
get initialized in a good safe way. And this bug is now fixed in the
efi.git tree, and will hopefully be backported to older kernels.
As the kernel recommends, the resultant seeds are 256 bits and are
allocated using pool memory of type EfiACPIReclaimMemory, so that it
gets freed at the right moment in boot.
Yu Watanabe
Zbigniew Jędrzejewski-Szmek
David Tardon
Luca Boccassi
Daan De Meyer
Lennart Poettering
msizanoen1
Christian Brauner
Mike Yuan
Mark Laws
Michal Sekletar
Pasha Vorobyev
Jason A. Donenfeld