Let's return the size in a return parameter instead of the return value.
And if NULL is specified this tells us the caller doesn't care about the
size and expects a NUL terminated string. In that case look for an
embedded NUL byte, and refuse in that case.
This should lock things down a bit, as we'll systematically refuse
embedded NUL strings now when we expect strings.
Supersedes #35308 (cherry-picked one commit and replaced the rest)
(I left a few comments that's folded by GitHub. Please make sure to
check them too.)
When removing a cgroup, we always want to eliminate subcgroups
first, i.e. use cg_trim(). And cg_rmdir() (along with
CGROUP_REMOVE flag) is simply unused. Kill it.
Opening pidfds for non thread group leaders only works from 6.9 onwards with PIDFD_THREAD. On
older kernels or without PIDFD_THREAD pidfd_open() fails with EINVAL. Since we might read non
thread group leader IDs from cgroup.threads, we introduce and set CGROUP_NO_PIDFD to avoid
trying open pidfd's for them and instead use the pid as is.
We can only delegate actual controllers, not the BPF pseudo-controllers
we defined as there's imply no concept for that. Hence, when users set
Delegate=yes to do a wildcard delegation, only delegate the regular
controllers.
This means that we won't bother with BPF stuff for such units where it's
entirelly unnecessary.
This is just like cg_is_delegate() but operates on an fd instead of a
cgroup path.
Sooner or later we should access cgroupfs mostly via fds rather than
paths, but we aren't there yet. But let's at least get started.
This setting indicates that the given unit wants to receive coredumps
for processes that crash within the cgroup of this unit. This setting
requires that Delegate= is also true, and therefore is only available
where Delegate= is available.
This will be used by systemd-coredump to support forwarding coredumps to
containers.
Currently we spawn services by forking a child process, doing a bunch
of work, and then exec'ing the service executable.
There are some advantages to this approach:
- quick: we immediately have access to all the enourmous amount of
state simply by virtue of sharing the memory with the parent
- easy to refactor and add features
- part of the same binary, will never be out of sync
There are however significant drawbacks:
- doing work after fork and before exec is against glibc's supported
case for several APIs we call
- copy-on-write trap: anytime any memory is touched in either parent
or child, a copy of that page will be triggered
- memory footprint of the child process will be memory footprint of
PID1, but using the cgroup memory limits of the unit
The last issue is especially problematic on resource constrained
systems where hard memory caps are enforced and swap is not allowed.
As soon as PID1 is under load, with no page out due to no swap, and a
service with a low MemoryMax= tries to start, hilarity ensues.
Add a new systemd-executor binary, that is able to receive all the
required state via memfd, deserialize it, prepare the appropriate
data structures and call exec_child.
Use posix_spawn which uses CLONE_VM + CLONE_VFORK, to ensure there is
no copy-on-write (same address space will be used, and parent process
will be frozen, until exec).
The sd-executor binary is pinned by FD on startup, so that we can
guarantee there will be no incompatibilities during upgrades.
systemd's own cgroup hierarchy is special to us, we use it to actually
manage processes. Because of that many calls tha apply to cgroups are
only ever called with the SYSTEMD_CGROUP_CONTROLLER as controller
argument. Let's hence remove the argument altogether.
This in particular touches the kill and xattr routines.
This changes no behaviour, we just drop an argument that is always set
to the same value anyway.
This is preparation to eventually getting rid of the cgroupvs1, because
on cgroupvs2 the cgroup paths do not change for different controllers,
there's only a single hierarchy there.
Let's clean up validation/escaping of cgroup names. i.e. split out code
that tests if name needs escaping. Return proper error codes, and extend
test a bit.
This function was moved from cgroup-util.c to cgroup-setup.c a while
back, but the prototype in the matching header files wasn't migrated.
Let's fix that.
From a given cgroup path, cg_path_get_unit() allows to retrieve the
unit's name. Although, this removes the path to the unit's cgroup,
preventing the result to be used to fetch xattrs.
Introduce cg_path_get_unit_path() which provides the path to the unit's
cgroup. This function behave similarly to cg_path_get_unit() (checking
the validity and escaping the unit's name).
The name "def.h" originates from before the rule of "no needless abbreviations"
was established. Let's rename the file to clarify that it contains a collection
of various semi-related constants.
It attaches the LSM BPF program when the system manager starts up.
It populates the hash of maps BPF map when services that have
RestrictFileSystems= set start.
It cleans up the hash of maps when the unit cgroup is pruned.
To pass the file descriptor of the BPF map we add it to the keep_fds
array.
This commit introduces all the logic to load and attach the BPF
programs to restrict network interfaces when a unit specifying it is
loaded.
Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>
Mike Yuan
Lennart Poettering
Zbigniew Jędrzejewski-Szmek
Daan De Meyer
Timo Rothenpieler
Yu Watanabe
Nick Rosbrook
Luca Boccassi
Quentin Deslandes
wineway
Michal Koutný
Iago Lopez Galeiras
Mauricio Vásquez
Albert Brox
Julia Kartseva
Benjamin Robin