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pid1: add ability to kill processes in a subgroup of a unit

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This is useful for things like machined, where the system machined wants
to manage a machine owned by the user somewhere down the tree.
This commit is contained in:
Lennart Poettering
2025-07-08 03:14:53 +02:00
parent 9afe65d974
commit 0f23564ad4
11 changed files with 183 additions and 50 deletions
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src/core/unit.c
+35 -14
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@@ -4041,6 +4041,7 @@ static int unit_kill_one(
int unit_kill(
Unit *u,
KillWhom whom,
const char *subgroup,
int signo,
int code,
int value,
@@ -4060,11 +4061,19 @@ int unit_kill(
assert(SIGNAL_VALID(signo));
assert(IN_SET(code, SI_USER, SI_QUEUE));
if (subgroup) {
if (!IN_SET(whom, KILL_CGROUP, KILL_CGROUP_FAIL))
return sd_bus_error_set(ret_error, SD_BUS_ERROR_NOT_SUPPORTED, "Killing by subgroup is only supported for 'cgroup' or 'cgroup-kill' modes.");
if (!unit_cgroup_delegate(u))
return sd_bus_error_set(ret_error, SD_BUS_ERROR_NOT_SUPPORTED, "Killing by subgroup is only available for units with control group delegation enabled.");
}
main_pid = unit_main_pid(u);
control_pid = unit_control_pid(u);
if (!UNIT_HAS_CGROUP_CONTEXT(u) && !main_pid && !control_pid)
return sd_bus_error_setf(ret_error, SD_BUS_ERROR_NOT_SUPPORTED, "Unit type does not support process killing.");
return sd_bus_error_set(ret_error, SD_BUS_ERROR_NOT_SUPPORTED, "Unit type does not support process killing.");
if (IN_SET(whom, KILL_MAIN, KILL_MAIN_FAIL)) {
if (!main_pid)
@@ -4095,46 +4104,58 @@ int unit_kill(
/* Note: if we shall enqueue rather than kill we won't do this via the cgroup mechanism, since it
* doesn't really make much sense (and given that enqueued values are a relatively expensive
* resource, and we shouldn't allow us to be subjects for such allocation sprees) */
if (IN_SET(whom, KILL_ALL, KILL_ALL_FAIL) && code == SI_USER) {
if (IN_SET(whom, KILL_ALL, KILL_ALL_FAIL, KILL_CGROUP, KILL_CGROUP_FAIL) && code == SI_USER) {
CGroupRuntime *crt = unit_get_cgroup_runtime(u);
if (crt && crt->cgroup_path) {
_cleanup_set_free_ Set *pid_set = NULL;
_cleanup_free_ char *joined = NULL;
const char *p;
if (empty_or_root(subgroup))
p = crt->cgroup_path;
else {
joined = path_join(crt->cgroup_path, subgroup);
if (!joined)
return -ENOMEM;
p = joined;
}
if (signo == SIGKILL) {
r = cg_kill_kernel_sigkill(crt->cgroup_path);
r = cg_kill_kernel_sigkill(p);
if (r >= 0) {
killed = true;
log_unit_info(u, "Killed unit cgroup with SIGKILL on client request.");
log_unit_info(u, "Killed unit cgroup '%s' with SIGKILL on client request.", p);
goto finish;
}
if (r != -EOPNOTSUPP) {
if (ret >= 0)
sd_bus_error_set_errnof(ret_error, r,
"Failed to kill unit cgroup: %m");
RET_GATHER(ret, log_unit_warning_errno(u, r, "Failed to kill unit cgroup: %m"));
RET_GATHER(ret, log_unit_warning_errno(u, r, "Failed to kill unit cgroup '%s': %m", p));
goto finish;
}
/* Fall back to manual enumeration */
} else {
/* Exclude the main/control pids from being killed via the cgroup if
* not SIGKILL */
} else if (IN_SET(whom, KILL_ALL, KILL_ALL_FAIL)) {
/* Exclude the main/control pids from being killed via the cgroup if not
* SIGKILL */
r = unit_pid_set(u, &pid_set);
if (r < 0)
return log_oom();
}
r = cg_kill_recursive(crt->cgroup_path, signo, 0, pid_set, kill_common_log, u);
r = cg_kill_recursive(p, signo, /* flags= */ 0, pid_set, kill_common_log, u);
if (r < 0 && !IN_SET(r, -ESRCH, -ENOENT)) {
if (ret >= 0)
sd_bus_error_set_errnof(
ret_error, r,
"Failed to send signal SIG%s to auxiliary processes: %m",
signal_to_string(signo));
"Failed to send signal SIG%s to processes in unit cgroup '%s': %m",
signal_to_string(signo), p);
RET_GATHER(ret, log_unit_warning_errno(
u, r,
"Failed to send signal SIG%s to auxiliary processes on client request: %m",
signal_to_string(signo)));
"Failed to send signal SIG%s to processes in unit cgroup '%s' on client request: %m",
signal_to_string(signo), p));
}
killed = killed || r > 0;
}
@@ -4142,7 +4163,7 @@ int unit_kill(
finish:
/* If the "fail" versions of the operation are requested, then complain if the set of processes we killed is empty */
if (ret >= 0 && !killed && IN_SET(whom, KILL_ALL_FAIL, KILL_CONTROL_FAIL, KILL_MAIN_FAIL))
if (ret >= 0 && !killed && IN_SET(whom, KILL_ALL_FAIL, KILL_CONTROL_FAIL, KILL_MAIN_FAIL, KILL_CGROUP_FAIL))
return sd_bus_error_set_const(ret_error, BUS_ERROR_NO_SUCH_PROCESS, "No matching processes to kill");
return ret;