Since 4c0d8d9673, most dlopen notes are
set at the beginning of the executables. Let's manage all dlopen notes
there, rather than setting them where dlopen is called.
Note that the only exceptions are the LIBBPF_NOTE for networkd and
nsresource. Since dlopen_bpf() is wrapped in an `#if` guard, the notes
are instead set within the corresponding functionality.
As a result, the DLOPEN_FOO() wrapper macros are no longer needed and
can be dropped completely.
This also switches all these notes to be defined via SD_ELF_NOTE_DLOPEN_ANCHORED().
Consequently, any notes added within unreachable or unused functions will be
automatically garbage-collected by the linker (--gc-sections) instead of
bloating the final binary.
E.g. unused p11-kit library dependency is now dropped from
systemd-repart.standalone binary.
Before:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE DESCRIPTION SONAME PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 recommended
blkid Support for block device identification libblkid.so.1 required
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 recommended
mount Support for mount enumeration libmount.so.1 required
fdisk Support for reading and writing partition tables libfdisk.so.1 required
blkid Support for block device identification libblkid.so.1 recommended
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 suggested
fdisk Support for reading and writing partition tables libfdisk.so.1 suggested
idn Support for internationalized domain names libidn2.so.0 suggested
mount Support for mount enumeration libmount.so.1 recommended
selinux Support for SELinux libselinux.so.1 recommended
tpm Support for TPM libtss2-esys.so.0 suggested
tpm Support for TPM libtss2-rc.so.0 suggested
tpm Support for TPM libtss2-mu.so.0 suggested
tpm Support for TPM libtss2-tcti-device.so.0 suggested
p11-kit Support for PKCS11 hardware tokens libp11-kit.so.0 suggested
```
After:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE DESCRIPTION SONAME PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 recommended
blkid Support for block device identification libblkid.so.1 required
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 recommended
mount Support for mount enumeration libmount.so.1 required
fdisk Support for reading and writing partition tables libfdisk.so.1 required
blkid Support for block device identification libblkid.so.1 recommended
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 suggested
fdisk Support for reading and writing partition tables libfdisk.so.1 suggested
mount Support for mount enumeration libmount.so.1 recommended
selinux Support for SELinux libselinux.so.1 recommended
tpm Support for TPM libtss2-esys.so.0 suggested
tpm Support for TPM libtss2-rc.so.0 suggested
tpm Support for TPM libtss2-mu.so.0 suggested
tpm Support for TPM libtss2-tcti-device.so.0 suggested
```
When a rate limit is armed, for example via StartLimitInterval=, and the
machine is suspended, the rate limit's "clock" is suspended as well,
since the elapse checks use CLOCK_MONOTONIC. This then causes unexpected
situations where a rate limit armed via StartLimitInterval=1h, followed
by a 10 hour suspend, would elapse after 11 hours total.
Let's avoid this by switching the rate limits to CLOCK_BOOTTIME, which
works the same as CLOCK_MONOTONIC, but accounts for the time spent in
suspend as well.
There's one slight concern when it comes to upgrade path - the old
"begin" value of the rate limit is stored as CLOCK_MONOTONIC, but after
upgrading systemd and serializing/deserializing the state it will be
suddenly compared against now(CLOCK_BOOTTIME), which might cause some
rate limits to elapse "prematurely". But this is just a one-time thing,
after which the rate limit timers should re-assess themselves.
Resolves: #42912
We have two concepts: a list of files that should be extracted from an
intermediate build artifact to be used in a later build artifact, and for a
given artifact, a list "donors". The first list was called "extract", because
it is passed to the .extract_objects() meson function, and the second was
called "objects", because that is the meson parameter to specify pre-built
objects files (6350d2dbd9). But this naming is
confusing: we don't care about the 'extract' step, this is something internal
to the build machinery. And 'objects' is a very generic term.
Let's use 'export' for the stuff that is "exported" for other binaries to use,
and 'import' to say where to import from. Those terms are symmetrical and the
association between them should be intuitive. (If you think the terms are
actually assymetrical, there are precedents for confusing the import with the
import sources. E.g. in modern English, turkeys are called so because they were
imported from the Americas and guineafowls were imported from Africa via
Türkiye and all that foreign stuff is alike.)
This makes each `foo_cflags` dependency define a `SYSTEMD_CFLAGS_MARKER_FOO`
macro, and checks if the macro is set when headers provided by external
libraries are included.
With this, we can fail fast at compile time if necessary `_cflags`
dependencies are omitted in meson.build. Missing dependencies found by this
mechanism have been added across the tree.
The new polkit will return a new detail regarding a successful
authentication: the actual result type, which we can use to
see whether the user authenticated as admin. This can be used
to grant additional privileges.
At various places we filter directory enumerations by inode type. Let's
add explicit support for that, so that the "struct dirent" array we
return already suppresses them.
This shortens code and makes things more robust.
The only runtime trigger for registry cleanup is the BPF kprobe that fires
on user namespace destruction; when it is missed (ring buffer overflow,
kprobe missing, fdstore entry dropped), the dead namespace's registry entry
survives and keeps its UID/GID ranges blocked until the manager restarts and
its startup sweep runs. The allocation hot path checked whether a candidate
range was already taken but never whether the namespace holding it was still
alive, so a single dead namespace could permanently starve an allocation.
This is most visible when a parent delegates its entire container UID window
to a child that then dies: every subsequent allocation from the parent fails
with NoDynamicRange even though the ranges are reclaimable.
Add userns_registry_reap_if_dead(), which probes a registered namespace's
liveness via the kernel namespace identifier recorded at allocation time and,
if it is authoritatively dead, releases its registry entry — restoring any
ranges it received via delegation to their ancestors. Call it from the
allocation availability check for both transient registrations and delegated
ranges, walking a chain of dead ancestors in the delegation case. This
mirrors the existing inode-slot stale cleanup and makes allocation
self-healing without waiting for a restart.
The startup sweep grew the same load-probe-release logic, so route it through
the new helper too; its errno return distinguishes alive, no-recorded-id, and
unprobeable-environment cases so the sweep keeps its early-out when lookup by
id isn't possible at all.
Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>
Switch the executable-owned call sites from the plain dlopen_<lib>()
helpers to the new DLOPEN_<LIB>() macros, so that each binary that loads
an optional library at runtime now carries its own .note.dlopen note
instead of relying solely on libsystemd-shared. Each call site passes a
priority reflecting whether it hard-depends on the library (required) or
degrades gracefully without it (recommended).
Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>
When a user namespace dies and its registry entry is torn down, the kernel
can recycle its inode number for a freshly-created namespace. A subsequent
registration or operation request can therefore find a stale registry entry
keyed by the same inode that actually belongs to a different, now-dead user
namespace.
Use NS_GET_ID to compare the kernel-assigned namespace identifier against
the stored one whenever we look up the registry from a live userns fd
(AddMount/AddControlGroup/AddNetworkInterface, plus the two registration
paths). Extract release_userns_by_info()/release_userns_by_inode() into
userns-registry.c so nsresourcework can fully clean up stale entries
(BPF allowlist, fdstore fd, cgroups, netifs, on-disk record) before reusing
the slot, and remove the now-unused userns_registry_inode_exists().
Co-developed-by: Claude Opus 4.7 <noreply@anthropic.com>
- **bpf-util: rename from bpf-dlopen, unify version-specific symbol
handling**
- **cryptsetup: dlopen libcryptsetup in tokens**
- **tree-wide: dlopen libpam in pam plugins**
- **test-bus-marshal: dlopen() glib and libdbus instead of linking
directly**
- **lock-util: Simplify timeout for lock_generic_with_timeout()**
- **color-util: simplify hsv_to_rgb, fix rgb_to_hsv negative-hue wrap**
- **tree-wide: Use our own macros instead of fabs()/fmax()/fmin()**
- **locale-util: dlopen() libintl instead of linking against it**
- **home: Use log2u64() over log2()**
- **meson: drop libdl, threads, and librt dependencies**
- **libc: Use dlsym() from a constructor instead of weak symbols**
- **libc: Make sure C23 versions of strtol(), sscanf() are not used**
Our baseline glibc is 2.34, which merged libdl, libpthread (the
dependency('threads') target), and librt into libc. Empty .so/.a stubs
remain for backward compatibility with old binaries, but new builds
resolve dl_*, pthread_*, mq_*, timer_*, etc. directly from libc.
On musl the same libraries are likewise empty stubs.
Drop the libdl, threads, and librt entries from every meson.build, and
remove the now-stale 'Libs.private: -lrt -pthread' from libudev.pc.in
since both flags resolve to empty link-time stubs on glibc 2.34+ and
musl.
Verified with readelf -d that libsystemd.so, libudev.so, and systemd no
longer carry DT_NEEDED entries for libdl/libpthread/librt.
Renames src/shared/bpf-dlopen.{c,h} to src/shared/bpf-util.{c,h} and
folds the former src/shared/bpf-compat.h (struct forward decl and
compat_bpf_map_create() helper) into the new header.
Aligns dlopen_bpf() with the standard wrapper pattern: drops the
manual dlopen_safe()/dlsym_many_or_warn()/TAKE_PTR(dl) plumbing and
the bespoke 'cached' int in favor of dlopen_many_sym_or_warn() inside
a FOREACH_STRING() soname-fallback loop.
Unifies declaration of the version-specific symbols (bpf_create_map,
bpf_map_create, bpf_object__next_map, bpf_token_create) into a single
DISABLE_WARNING_REDUNDANT_DECLS block in the header, and alphabetically
merges the DLSYM_PROTOTYPE list. DLSYM_OPTIONAL is used to load each
one — call sites already handle NULL (compat_bpf_map_create() and the
sym_bpf_object__next_map guard in userns-restrict.c). bpf_token_create
additionally defaults to a missing_bpf_token_create() stub returning
-ENOSYS, so callers can branch on the errno instead of NULL-checking
the pointer.
Updates test-bpf-token to match: drops the compile-time
LIBBPF_MAJOR_VERSION ≥ 1.5 gate and the direct <bpf/bpf.h> include in
favor of dlopen_bpf() + sym_bpf_token_create(), and treats -ENOSYS as
the test-skip path (covering both 'libbpf too old' and 'kernel lacks
BPF_TOKEN_CREATE support').
The BPF kprobe that fires on user namespace destruction is the only thing
that triggers registry cleanup, so any time it doesn't run — ring buffer
overflow, kprobe missing, fdstore entry dropped outside our cleanup path
— a registry entry is left behind forever.
Stamp each registry entry with the kernel's unique namespace identifier
(NS_GET_ID, kernel ≥ 6.13) at allocation time. At manager startup, after
the existing fdstore→registry sweep, walk the registry and ask the kernel
to look each namespace up by id via open_by_handle_at() on nsfs; if the
lookup returns -ESTALE the namespace is gone and we release the entry.
Old entries written before this change carry no identifier and are left
alone.
Add a namespace_open_by_id() helper for the lookup. The kernel restricts
open_by_handle_at() on nsfs to processes in the initial user namespace,
collapsing both permission denials and dead namespaces onto -ESTALE; the
helper refuses early with -EHOSTDOWN outside the initial user namespace
so callers can tell the two apart.
userns_registry_remove() restores a sub-delegated UID range by writing
the previous owner's data to u<UID>.delegate with WRITE_STRING_FILE_ATOMIC.
Atomic writes go via a temp file and rename, which replaces the directory
entry with a fresh inode and severs the hardlink to g<GID>.delegate. The
stale GID side then keeps pointing at the prior inode with outdated owner
and ancestor data, so subsequent lookups via GID return wrong results.
Re-create the hardlink after the atomic write so the two views stay in
sync, matching what userns_registry_store() already does after writing
a new delegation.
Every dlopen_xxx() helper now takes an int log_level argument. It is
passed through to dlopen_many_sym_or_warn() (which in turn propagates it
to dlopen_verbose() for the library-not-installed case), and is used by
the fallback stub when support for the library is not compiled in to
emit a "<lib> support is not compiled in." message at the caller's level.
Callers pass LOG_DEBUG when gracefully degrading, or a higher level when
the failure should surface, and no longer need to log redundantly at the
call site.
As part of this, dlopen_bpf_full() (which already took a log_level) is
merged into dlopen_bpf() rather than keeping both.
The static inline fallbacks used to live in the headers, which required
pulling log.h in from every header that declared a dlopen_xxx(). Move
them into the .c files instead: the declaration is always outside the
#if HAVE_XXX block, the impl sits outside the outer #if HAVE_XXX wrap
with its own internal #if HAVE_XXX/#else/#endif, and apparmor-util.c,
idn-util.c, libmount-util.c and pam-util.c are now always compiled so
they can host their stubs.
The six .bpf.c files and their shared .bpf.h headers now live directly
under src/bpf/, rather than scattered across src/core/bpf/<prog>/,
src/network/bpf/<prog>/ and src/nsresourced/bpf/<prog>/.
All BPF compilation logic — the BPF_FRAMEWORK determination (clang/gcc/
bpftool/llvm-strip lookups), flag and command construction, vmlinux.h
handling, the bpf_programs list and the loop that builds the unstripped
object, the stripped object and the skeleton header for each program —
moves into src/bpf/meson.build. The top-level meson.build only keeps
option handling and the libbpf dependency. subdir('src/bpf') is pulled
up before config.h generation so that BPF_FRAMEWORK, HAVE_VMLINUX_H and
ENABLE_SYSCTL_BPF land in conf in time.
Skeleton wrapper headers (<prog>-skel.h) are now emitted by a
configure_file() template (src/bpf/bpf-skel-wrapper.h.in) at meson
setup, replacing the previously checked-in shims of the same name.
Consumer #include paths are flattened:
"bpf/<prog>/<prog>-skel.h" becomes "<prog>-skel.h",
"bpf/<prog>/<prog>-api.bpf.h" becomes "<prog>-api.bpf.h". src/bpf is
added to includes so the shared BPF headers resolve.
sysctl-write-event.h, now shared between userspace (networkd-sysctl.c)
and BPF (sysctl-monitor.bpf.c) from a single location, gains guarded
includes so pid_t and uint64_t resolve on both sides: vmlinux.h in the
BPF case (selected via __bpf__), stdint.h + sys/types.h otherwise.
The updated parsing_hacks.h file uncovered a bunch of extra
things that the check-pointer-deref coccinelle script flags.
This commit fixes them to make the tree check-pointer-deref clean.
This is very noisy as there's a dozen of these message every
time it gets called, and it's not really an error but an
expected situation, so downgrade from info to debug
Whenever delegating UID ranges to a user namespace, it can also be
useful to map the foreign UID range, so that the container running in
the user namespace with delegated UID ranges can download container
images and unpack them to the foreign UID range.
Let's add an option mapForeign to make this possible. Note that this option
gives unprivileged users full access to the any foreign UID range owned directory
that they can access. Hence it is recommended (and already was recommended) to
store foreign UID range owned directories in a 0700 directory owned by the
owner of the tree to avoid access and modifications by other users.
This is already the case for the main users of the foreign UID range,
namely /var/lib/machines, /var/lib/portables and /home/<user> which all
use 0700 as their mode.
Users will also be able to create foreign UID range owned inodes in any
directories their own user can write to (on most systems this means /tmp,
/var/tmp and /home/<user>).
mkosi does all of its environment setup in an unprivileged user
namespace with an identity mapping. When it invokes nspawn and nspawn
tries to get a transient userns from nsresourced, this fails as no
transient ranges are mapped into mkosi's unprivileged userns (as doing
so would require privileges).
To fix this problem, let's allow allocating unprivileged self user
namespaces in nsresourced, similar to what the kernel allows, except that
we also support delegations for these. This means that mkosi can get its
unprivileged userns as before from nsresourced, but it can also request a
delegated 64K range inside that userns as well, which nsresourced can then
allocate to nspawn later when it asks for one.
Similar to the kernel, we disallow setgroups for self mappings. However,
instead of doing this via /proc/self/setgroups, which applies to the current
user namespace and all its child user namespaces, we use the BPF LSM to deny
setgroups instead, so that it can still be allowed for child user namespaces.
We need this because as soon as a container launches in a child user namespace
using one of the delegated mappings, it has to be able to do setgroups() to be
able to function properly.
To allow mapping the root user, we need to add the CAP_SETFCAP capability to
nsresourced.
We want to support the scenario where we bind mount the nsresourced
varlink socket into a container to allow nested containers where the
outer container runs in its own transient range from nsresourced but
can still allocate transient ranges for its own nested containers.
To support this use case let's add support for delegation. Delegated
ranges are allocated when allocating the primary range and are propagated
1:1 to the user namespace. We track delegated ranges in ".delegate" files
in the userns registry so that they can't be used for other range allocations.
We make one exception for delegated ranges though, if we get a request from
a user namespace that is a child of the user namespace that owns the delegated
ranges, we allow allocating from the delegated range. The parent userns already
has full ownership over the child userns, so it doesn't matter that the parent
userns and the child userns share the same range. This allows making use of
delegated ranges without having to run another copy of nsresourced inside the
parent userns to hand out from the delegated range.
To support recursive delegations, we keep track of the previous owners of the
delegated range and restore ownership to the last previous owner when the current
owner is freed.
The purpose of the userns-restrict BPF-LSM program is to prevent the
transient ranges leaking to disk, so let's allow operations outside the
transient UID ranges, even if the mount is not allowlisted.
This is preparation for the next commits where we'll add support for mapping
the current user and the foreign UID range into the user namespaces provisioned
by nsresourced. Operations creating files/directories as these UIDs/GIDs should
not need the corresponding mount to be allowlisted with nsresourced.
The code here assumes that free_user_ns() is called for every single
user namespace. That however has never been the case and the logic for
free_user_ns() is a bit more involved.
A nested user namespace pins its parent user namespace. IOW, the
lifetime of the parent user namespaces is at least as long as the child
user namespaces.
If a parent user namespace becomes unused (no namespace file descriptors
or task using it anymore) then it will stick around and its lifetime
still bound to the child user namespace.
free_user_ns() takes advantage of that behavior. If a child user
namespace is freed and its parent user namespace is already unused then
then free_user_ns() will free both the child and the parent user
namespace. This means a single free_user_ns() frees two user namespaces.
Hence, the bpf program never sees the parent user namespace being freed.
We can fix this by piggy-backing on another function that is called for
every single user namespace being freed. This requires CONFIG_SYSCTL but
systemd doesn't work without that anyway.
The return type needs to change to a scalar type as required by libbpf.
Long-term what we need is appropriate LSM infrastructure for this
including hooks that get called on namespace destruction.
Thanks to Daan DeMeyer for figuring out that the cast is needed.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Now that sd-event doesn't insist on blocking
SIGCHLD anymore when watching for process exit,
let's stop blocking SIGCHLD tree-wide where not
required anymore.
Quite often we need to specify include_directories('.'). Normally, meson
does this automatically, but we specify implicit_include_directories : false,
see 30d20907bd for an explanation.
Passing the include_directories argument through the template layers was rather
cumbersome. Let's simplify things by always including the directory of the
first source file. This makes the definitions simpler, at the cost of having an
unnecessary include directory in the list in some cases.
(Tests are excluded from this change, because they happen to not need this, but
also because some tests have source[0] which is a custom target, and we'd need
newer meson to support that.)
In all cases, everything that we list in 'extract', we also list in
'sources'. We can simplify things by automatically appending the first
list to the second.
In the listings, move 'extract' key right below 'sources', since now
they are both "sources", just with slightly different meanings.
Yu Watanabe
Lennart Poettering
Frantisek Sumsal
Zbigniew Jędrzejewski-Szmek
Luca Boccassi
Daan De Meyer
Diego Viola
Michael Vogt
Clayton Craft
Daan De Meyer
Christian Brauner
Zbigniew Jędrzejewski-Szmek
Jelle van der Waa