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notify: beef up --pid= logic #15642

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Apr 30, 2020
Merged

notify: beef up --pid= logic #15642

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13 changes: 7 additions & 6 deletions man/systemd-notify.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -84,12 +84,13 @@
<varlistentry>
<term><option>--pid=</option></term>

<listitem><para>Inform the init system about the main PID of
the daemon. Takes a PID as argument. If the argument is
omitted, the PID of the process that invoked
<command>systemd-notify</command> is used. This is equivalent
to <command>systemd-notify MAINPID=$PID</command>. For details
about the semantics of this option see
<listitem><para>Inform the service manager about the main PID of the daemon. Takes a PID as
argument. If the argument is specified as <literal>auto</literal> or omitted, the PID of the process
that invoked <command>systemd-notify</command> is used, except if that's the service manager. If the
argument is specified as <literal>self</literal>, the PID of the <command>systemd-notify</command>
command itself is used, and if <literal>parent</literal> is specified the calling process' PID is
used — even if it is the service manager. This is equivalent to <command>systemd-notify
MAINPID=$PID</command>. For details about the semantics of this option see
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para></listitem>
</varlistentry>

Expand Down
55 changes: 49 additions & 6 deletions src/notify/notify.c
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,26 @@ static int help(void) {
return 0;
}

static pid_t manager_pid(void) {
const char *e;
pid_t pid;
int r;

/* If we run as a service managed by systemd --user the $MANAGERPID environment variable points to
* the service manager's PID. */
e = getenv("MANAGERPID");
if (!e)
return 0;

r = parse_pid(e, &pid);
if (r < 0) {
log_warning_errno(r, "$MANAGERPID is set to an invalid PID, ignoring: %s", e);
return 0;
}

return pid;
}

static int parse_argv(int argc, char *argv[]) {

enum {
Expand Down Expand Up @@ -96,13 +116,24 @@ static int parse_argv(int argc, char *argv[]) {
break;

case ARG_PID:
if (isempty(optarg) || streq(optarg, "auto")) {
arg_pid = getppid();

if (optarg) {
if (parse_pid(optarg, &arg_pid) < 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Failed to parse PID %s.", optarg);
} else
if (arg_pid <= 1 ||
arg_pid == manager_pid()) /* Don't send from PID 1 or the service
* manager's PID (which might be distinct from
* 1, if we are a --user instance), that'd just
* be confusing for the service manager */
arg_pid = getpid();
} else if (streq(optarg, "parent"))
arg_pid = getppid();
else if (streq(optarg, "self"))
arg_pid = getpid();
else {
r = parse_pid(optarg, &arg_pid);
if (r < 0)
return log_error_errno(r, "Failed to parse PID %s.", optarg);
}

break;

Expand Down Expand Up @@ -151,6 +182,7 @@ static int run(int argc, char* argv[]) {
_cleanup_strv_free_ char **final_env = NULL;
char* our_env[4];
unsigned i = 0;
pid_t source_pid;
int r;

log_show_color(true);
Expand Down Expand Up @@ -207,7 +239,18 @@ static int run(int argc, char* argv[]) {
setreuid(arg_uid, (uid_t) -1) < 0)
return log_error_errno(errno, "Failed to change UID: %m");

r = sd_pid_notify(arg_pid ? arg_pid : getppid(), false, n);
if (arg_pid > 0)
source_pid = arg_pid;
else {
/* Pretend the message originates from our parent, given that we are typically called from a
* shell script, i.e. we are not the main process of a service but only a child of it. */
source_pid = getppid();
if (source_pid <= 1 ||
source_pid == manager_pid()) /* safety check: don't claim we'd send anything from PID 1
* or the service manager itself */
source_pid = 0;
}
r = sd_pid_notify(source_pid, false, n);
if (r < 0)
return log_error_errno(r, "Failed to notify init system: %m");
if (r == 0)
Expand Down