Let's generalize this, so that we can use this in nspawn later on, which
is pretty useful as we need to be able to mask files from the inner
child of nspawn too, where the host's /run/systemd/inaccessible
directory is not visible anymore. Moreover, if nspawn can create these
nodes on its own before the payload this means the payload can run with
fewer privileges.
This removes the ability to configure which cgroup controllers to mount
together. Instead, we'll now hardcode that "cpu" and "cpuacct" are
mounted together as well as "net_cls" and "net_prio".
The concept of mounting controllers together has no future as it does
not exist to cgroupsv2. Moreover, the current logic is systematically
broken, as revealed by the discussions in #10507. Also, we surveyed Red
Hat customers and couldn't find a single user of the concept (which
isn't particularly surprising, as it is broken...)
This reduced the (already way too complex) cgroup handling for us, since
we now know whenever we make a change to a cgroup for one controller to
which other controllers it applies.
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
Let's always write "1 << 0", "1 << 1" and so on, except where we need
more than 31 flag bits, where we write "UINT64(1) << 0", and so on to force
64bit values.
if we lack privs to create device nodes that's fine, and creating
/run/systemd/inaccessible/chr or /run/systemd/inaccessible/blk won't
work then. Document this in longer comments.
Fixes: #4484
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
The initial fix for relabelling the cgroup filesystem for
SELinux delivered in commit 8739f23e3 was based on the assumption that
the cgroup filesystem is already populated once mount_setup() is
executed, which was true for my system. What I wasn't aware is that this
is the case only when another instance of systemd was running before
this one, which can happen if systemd is used in the initrd (for ex. by
dracut).
In case of a clean systemd start-up the cgroup filesystem is actually
being populated after mount_setup() and does not need relabelling as at
that moment the SELinux policy is already loaded. Since however the root
cgroup filesystem was remounted read-only in the meantime this operation
will now fail.
To fix this check for the filesystem mount flags before relabelling and
only remount ro->rw->ro if necessary and leave the filesystem read-write
otherwise.
Fixes#7901.
This reworks the SELinux and SMACK label fixing calls in a number of
ways:
1. The two separate boolean arguments of these functions are converted
into a flags type LabelFixFlags.
2. The operations are now implemented based on O_PATH. This should
resolve TTOCTTOU races between determining the label for the file
system object and applying it, as it it allows to pin the object
while we are operating on it.
3. When changing a label fails we'll query the label previously set, and
if matches what we want to set anyway we'll suppress the error.
Also, all calls to label_fix() are now (void)ified, when we ignore the
return values.
Fixes: #8566
This macro will read a pointer of any type, return it, and set the
pointer to NULL. This is useful as an explicit concept of passing
ownership of a memory area between pointers.
This takes inspiration from Rust:
https://doc.rust-lang.org/std/option/enum.Option.html#method.take
and was suggested by Alan Jenkins (@sourcejedi).
It drops ~160 lines of code from our codebase, which makes me like it.
Also, I think it clarifies passing of ownership, and thus helps
readability a bit (at least for the initiated who know the new macro)
So far, for all our API VFS mounts we used the fstype also as mount
source, let's do that for the cgroupsv2 mounts too. The kernel doesn't
really care about the source for API VFS, but it's visible to the user,
hence let's clean this up and follow the rule we otherwise follow.
We make heavy use of BPF functionality these days, hence expose the BPF
file system too by default now. (Note however, that we don't actually
make use bpf file systems object yet, but we might later on too.)
When using SELinux with legacy cgroups the tmpfs on /sys/fs/cgroup is by
default labelled as tmpfs_t. This label is also inherited by the "cpu"
and "cpuacct" symbolic links. Unfortunately the policy expects them to
be labelled as cgroup_t, which is used for all the actual cgroup
filesystems. Failure to do so results in a stream of denials.
This state cannot be fixed reliably when the cgroup filesystem structure
is set-up as the SELinux policy is not yet loaded at this
moment. It also cannot be fixed later as the root of the cgroup
filesystem is remounted read-only. In order to fix it the root of the
cgroup filesystem needs to be temporary remounted read-write, relabelled
and remounted back read-only.
When systemd is running inside a container employing user
namespaces it currently mounts the unified cgroup hierarchy
without being able to write to it. This causes systemd to
freeze during boot.
This patch checks whether the unified cgroup hierarchy
is writable. If it is not it will not mount it.
This solution is based on a patch by Evgeny Vereshchagin.
Closes#6408.
Closes https://github.com/lxc/lxc/issues/1678 .
The advantage is that is the name is mispellt, cpp will warn us.
$ git grep -Ee "conf.set\('(HAVE|ENABLE)_" -l|xargs sed -r -i "s/conf.set\('(HAVE|ENABLE)_/conf.set10('\1_/"
$ git grep -Ee '#ifn?def (HAVE|ENABLE)' -l|xargs sed -r -i 's/#ifdef (HAVE|ENABLE)/#if \1/; s/#ifndef (HAVE|ENABLE)/#if ! \1/;'
$ git grep -Ee 'if.*defined\(HAVE' -l|xargs sed -i -r 's/defined\((HAVE_[A-Z0-9_]*)\)/\1/g'
$ git grep -Ee 'if.*defined\(ENABLE' -l|xargs sed -i -r 's/defined\((ENABLE_[A-Z0-9_]*)\)/\1/g'
+ manual changes to meson.build
squash! build-sys: use #if Y instead of #ifdef Y everywhere
v2:
- fix incorrect setting of HAVE_LIBIDN2
cgroup namespace wasn't useful for delegation because it allowed resource
control interface files (e.g. memory.high) to be written from inside the
namespace - this allowed the namespace parent's resource distribution to be
disturbed by its namespace-scoped children.
A new mount option, "nsdelegate", was added to cgroup v2 to address this issue.
The flag is meangingful only when mounting cgroup v2 in the init namespace and
makes a cgroup namespace a delegation boundary. The kernel feature is pending
for v4.13.
This should have been the default behavior on cgroup namespaces and this commit
makes systemd try "nsdelegate" first when trying to mount cgroup v2 and fall
back if the option is not supported.
Note that this has danger of breaking usages which depend on modifying the
parent's resource settings from the namespace root, which isn't a valid thing
to do, but such usages may still exist.
We need this to gracefully support older or strangely configured kernels.
v2:
- do not install a callback handler, just embed the right conditions into
cg_is_*_wanted()
v3:
- fix bug in cg_is_legacy_wanted()
Currently the hybrid mode mounts cgroup v2 on /sys/fs/cgroup instead of the v1
name=systemd hierarchy. While this works fine for systemd itself, it breaks
tools which expect cgroup v1 hierarchy on /sys/fs/cgroup/systemd.
This patch updates the hybrid mode so that it mounts v2 hierarchy on
/sys/fs/cgroup/unified and keeps v1 "name=systemd" hierarchy on
/sys/fs/cgroup/systemd for compatibility. systemd itself doesn't depend on the
"name=systemd" hierarchy at all. All operations take place on the v2 hierarchy
as before but the v1 hierarchy is kept in sync so that any tools which expect
it to be there can keep doing so. This allows systemd to take advantage of
cgroup v2 process management without requiring other tools to be aware of the
hybrid mode.
The hybrid mode is implemented by mapping the special systemd controller to
/sys/fs/cgroup/unified and making the basic cgroup utility operations -
cg_attach(), cg_create(), cg_rmdir() and cg_trim() - also operate on the
/sys/fs/cgroup/systemd hierarchy whenever the cgroup2 hierarchy is updated.
While a bit messy, this will allow dropping complications from using cgroup v1
for process management a lot sooner than otherwise possible which should make
it a net gain in terms of maintainability.
v2: Fixed !cgns breakage reported by @evverx and renamed the unified mount
point to /sys/fs/cgroup/unified as suggested by @brauner.
v3: chown the compat hierarchy too on delegation. Suggested by @evverx.
v4: [zj]
- drop the change to default, full "legacy" is still the default.
Let's use chase_symlinks() everywhere, and stop using GNU
canonicalize_file_name() everywhere. For most cases this should not change
behaviour, however increase exposure of our function to get better tested. Most
importantly in a few cases (most notably nspawn) it can take the correct root
directory into account when chasing symlinks.
Currently, systemd uses either the legacy hierarchies or the unified hierarchy.
When the legacy hierarchies are used, systemd uses a named legacy hierarchy
mounted on /sys/fs/cgroup/systemd without any kernel controllers for process
management. Due to the shortcomings in the legacy hierarchy, this involves a
lot of workarounds and complexities.
Because the unified hierarchy can be mounted and used in parallel to legacy
hierarchies, there's no reason for systemd to use a legacy hierarchy for
management even if the kernel resource controllers need to be mounted on legacy
hierarchies. It can simply mount the unified hierarchy under
/sys/fs/cgroup/systemd and use it without affecting other legacy hierarchies.
This disables a significant amount of fragile workaround logics and would allow
using features which depend on the unified hierarchy membership such bpf cgroup
v2 membership test. In time, this would also allow deleting the said
complexities.
This patch updates systemd so that it prefers the unified hierarchy for the
systemd cgroup controller hierarchy when legacy hierarchies are used for kernel
resource controllers.
* cg_unified(@controller) is introduced which tests whether the specific
controller in on unified hierarchy and used to choose the unified hierarchy
code path for process and service management when available. Kernel
controller specific operations remain gated by cg_all_unified().
* "systemd.legacy_systemd_cgroup_controller" kernel argument can be used to
force the use of legacy hierarchy for systemd cgroup controller.
* nspawn: By default nspawn uses the same hierarchies as the host. If
UNIFIED_CGROUP_HIERARCHY is set to 1, unified hierarchy is used for all. If
0, legacy for all.
* nspawn: arg_unified_cgroup_hierarchy is made an enum and now encodes one of
three options - legacy, only systemd controller on unified, and unified. The
value is passed into mount setup functions and controls cgroup configuration.
* nspawn: Interpretation of SYSTEMD_CGROUP_CONTROLLER to the actual mount
option is moved to mount_legacy_cgroup_hierarchy() so that it can take an
appropriate action depending on the configuration of the host.
v2: - CGroupUnified enum replaces open coded integer values to indicate the
cgroup operation mode.
- Various style updates.
v3: Fixed a bug in detect_unified_cgroup_hierarchy() introduced during v2.
v4: Restored legacy container on unified host support and fixed another bug in
detect_unified_cgroup_hierarchy().
Despite the name, `Read{Write,Only}Directories=` already allows for
regular file paths to be masked. This commit adds the same behavior
to `InaccessibleDirectories=` and makes it explicit in the doc.
This patch introduces `/run/systemd/inaccessible/{reg,dir,chr,blk,fifo,sock}`
{dile,device}nodes and mounts on the appropriate one the paths specified
in `InacessibleDirectories=`.
Based on Luca's patch from https://github.com/systemd/systemd/pull/3327
Delete the dbus1 generator and some critical wiring. This prevents
kdbus from being loaded or detected. As such, it will never be used,
even if the user still has a useful kdbus module loaded on their system.
Sort of fixes#3480. Not really, but it's better than the current state.
daemons, which wish to transition state from the initramfs to the real
root, might use /dev/shm for their state.
As /dev is not relabeled across mount points, /dev/shm has to be
relabled explicitly.
Since Linux v4.4-rc1, __DEVEL__sane_behavior does not exist anymore and
is replaced by a new fstype "cgroup2".
With this patch, systemd no longer supports the old (unstable) way of
doing unified hierarchy with __DEVEL__sane_behavior and systemd now
requires Linux v4.4 for unified hierarchy.
Non-unified hierarchy is still the default and is unchanged by this
patch.
67e9c74b8a
We really shouldn't fail silently, but print a log message about these errors. Also make sure to attach error codes to
all log messages where that makes sense.
(While we are at it, add a couple of (void) casts to functions where we knowingly ignore return values.)
The mount_setup_early() and mount_setup() contain almost the same
pieces of code which calls mount_one() for a certain mount point
from the mount_table. This patch introduces mount_points_setup()
helper to prevent code duplication.
The code introduced in f8c1a81c51 (= systemd 227) failed for me with:
Failed to copy smack label from net_cls to /sys/fs/cgroup/net_cls: No such file or directory
There is no need for a symlink in this case because source and target
are identical. The symlink() call is allowed to fail when the target
already exists. When that happens, copying the Smack label must be
skipped.
But the code also failed when there is a symlink, like "cpu ->
cpu,cpuacct", because mac_smack_copy() got called with
src="cpu,cpuacct" which fails to find the entry because the current
directory is not inside /sys/fs/cgroup. The absolute path to the existing
entry must be used instead.
Make sure to propagate error codes from mount-loops correctly. Right now,
we return the return-code of the first mount that did _something_. This is
not what we want. Make sure we return an error if _any_ mount fails (and
then make sure to return the first error to not hide proper errors due to
consequential errors like -ENOTDIR).
Reported by cee1 <fykcee1@gmail.com>.
Even though systemd has its own smack label since
'--with-smack-run-label' configuration is set, the smack label of each
CGROUP root directory should have the star (i.e. *) label. This is
mainly because current Linux Kernel set the label in this way.
(Refer to smack_d_instantiate() in security/smack/smack_lsm.c)
However, if systemd has its own smack label and arg_join_controllers is
explicitly set or initialized by initialize_join_controllers() function,
current systemd creates the symlink in CGROUP root directory with its
own smack label as below.
lrwxrwxrwx. 1 root root System 11 Dec 31 16:00 cpu -> cpu,cpuacct
dr-xr-xr-x. 4 root root * 0 Dec 31 16:01 cpu,cpuacct
lrwxrwxrwx. 1 root root System 11 Dec 31 16:00 cpuacct -> cpu,cpuacct
This patch fixes that bug by copying the smack label from the origin.
