Now that we dlopen() so many deps, it might happen by accident that we
end up dlopen()ening stuff when we entered a container, which we should
really avoid, to not mix host and container libraries.
Let's add a global variable we can set when we want to block dlopen() to
ever succeed. This is then checked primarily in
dlopen_many_sym_or_warn(), where we'll generate EPERM plus a log
message.
There are a couple of other places we invoke dlopen(), without going
through dlopen_many_sym_or_warn(). This adds the same check there.
When inheriting file descriptors for stdout/stderr (either from stdin
or when making stderr inherit from stdout), we previously just assumed
they would be writable and dup'd them. This could lead to broken setups
if the inherited FD was actually opened read-only.
Before dup'ing any inherited FDs to stdout/stderr, verify they are
actually writable using the new fd_is_writable() helper. If not, fall
back to /dev/null (or reopen the terminal in the TTY case) with a
warning, rather than silently creating a broken setup where output
operations would fail.
$ sudo build/systemd-run --uid=asdf whoami
$ journalctl -e
(whoami)[1007784]: run-p1007782-i5200512.service: Failed to determine user credentials: No such process
(whoami)[1007784]: run-p1007782-i5200512.service: Failed at step USER spawning /usr/sbin/whoami: No such process
systemd[1]: run-p1007782-i5200512.service: Main process exited, code=exited, status=217/USER
systemd[1]: run-p1007782-i5200512.service: Failed with result 'exit-code'.
Now:
(whoami)[1013204]: run-p1013202-i5205932.service: Failed to determine credentials for user 'asdf': Unknown user
(whoami)[1013204]: run-p1013202-i5205932.service: Failed at step USER spawning /usr/sbin/whoami: Invalid argument
systemd[1]: run-p1013202-i5205932.service: Main process exited, code=exited, status=217/USER
systemd[1]: run-p1013202-i5205932.service: Failed with result 'exit-code'.
sys/prctl.h anyway includes linux/prctl.h and actually these .c files
includes sys/prctl.h. Hence, it is not necessary to explicitly include
linux/prctl.h.
Follow-up for 379d9ae222
After the commit, the functions are only used to determine
whether journals shall be forwarded to selected targets,
hence rename as such and remove effectively unused condition
on EXEC_OUTPUT_TTY.
Fixes#38486 again, which was fixed by
1405d46bf9, but regressed again by
f875a8026e.
This also make it use exec_input_is_terminal().
Follow-up for f875a8026e.
Commit 38748596f0 ("core: Make DelegateNamespaces= work for user
managers with CAP_SYS_ADMIN") refactored the logic for when an
unprivileged process should create a new user namespace for sandboxing.
This refactor inadvertently removed a check (`params->runtime_scope !=
RUNTIME_SCOPE_USER`) that differentiated between system services and user
services.
This causes a regression in rootless containers where systemd runs
unprivileged. When starting a system service (like `dbus-broker`) that
uses sandboxing features (eg. with `PrivateTmp=yes`), systemd now
incorrectly creates a new, minimal `PRIVATE_USERS_SELF` namespace.
This new namespace only maps UID/GID 0. When dbus-broker attempts to
drop privileges to the `dbus` user (GID 81), the `setresgid(81, 81, 81)`
call fails because GID 81 is not mapped.
Restore the check to ensure that the special unprivileged sandboxing
logic is only applied to user services, as was the original intent.
System services in a rootless context will now correctly run in the
container's main user namespace, where all necessary UIDs/GIDs are
mapped.
Fixes: https://github.com/systemd/systemd/issues/39563
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2391343
This allows a service to reuse the user namespace created for an
existing service, similarly to NetworkNamespacePath=. The configuration
is the initial user namespace (e.g. ID mapping) is preserved.
RootDirectory= but via a open_tree() file descriptor. This allows
setting up the execution environment for a service by the client in a
mount namespace and then starting a transient unit in that execution
environment using the new property.
We also add --root-directory= and --same-root-dir= to systemd-run to
have it run services within the given root directory. As systemd-run
might be invoked from a different mount namespace than what systemd is
running in, systemd-run opens the given path with open_tree() and then
sends it to systemd using the new RootDirectoryFileDescriptor= property.
RootDirectory= but via a open_tree() file descriptor. This allows
setting up the execution environment for a service by the client in
a mount namespace and then starting a transient unit in that execution
environment using the new property.
We also add --root-directory= and --same-root-dir= to systemd-run to
have it run services within the given root directory. As systemd-run
might be invoked from a different mount namespace than what systemd is
running in, systemd-run opens the given path with open_tree() and then
sends it to systemd using the new RootDirectoryFileDescriptor= property.
Hardcoding total size of the array is error-prone, especially
considering the exeuctable_fd is added far below, so the '4' is
not entirely obvious. Also we seldomly do VLAs.
The distinction between fdstore and extra fds is only meaningful
to struct Service. As far as executor is concerned they're just
some fds to pass to the service. Let's just merge it hence,
for the sake of simplicity.
According to systemd.exec(5):
> The fd:name option connects standard input to a specific, named
> file descriptor provided *by a socket unit*. ...
Currently however we're looking at the whole fd array passed,
fix it.
Previously, we limit the length of process name by 8.
This relax the restriction then at least process comm or
program_invocation_name contains the untrucated process name.
Closes#38367.
Although extremely unlikely, there is a race present in solely checking the
$LISTEN_PID environment variable, due to PID recycling. Fix that by introducing
$LISTEN_PIDFDID, which contains the 64-bit ID of a pidfd for the child process
that is not subject to recycling.
RootDirectory= and other options already implicitly enable PrivateUsers=
since 6ef721cbc7 if they are set in user
units, so that they can work out of the box.
Now with mountfsd support we can do the same for the images settings,
so enable them and document them.
Mike Yuan
Yu Watanabe
Lennart Poettering
Daan De Meyer
Chris Down
Zbigniew Jędrzejewski-Szmek
Quentin Deslandes
Daniel Foster
Luca Boccassi
Luca Boccassi