sd-bus: properly handle creds that are known but undefined for a process

A number of fields do not apply to all processes, including: there a
processes without a controlling tty, without parent process, without
service, user services or session. To distuingish these cases from the
case where we simply don't have the data, always return ENXIO for them,
while returning ENODATA for the case where we really lack the
information.

Also update the credentials dumping code to show this properly. Fields
that are known but do not apply are now shown as "n/a".

Note that this also changes some of the calls in process-util.c and
cgroup-util.c to return ENXIO for these cases.

1 files changed, 40 insertions, 30 deletions

diff --git a/src/libsystemd/sd-bus/bus-dump.c b/src/libsystemd/sd-bus/bus-dump.c
index 396bf36f8a..47a5c6b3a8 100644
--- a/src/libsystemd/sd-bus/bus-dump.c
+++ b/src/libsystemd/sd-bus/bus-dump.c
@@ -331,13 +331,11 @@ static void dump_capabilities(
 }
 
 int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
-        bool audit_sessionid_is_set = false, audit_loginuid_is_set = false;
-        const char *u = NULL, *uu = NULL, *s = NULL, *sl = NULL;
         uid_t owner, audit_loginuid;
         uint32_t audit_sessionid;
         char **cmdline = NULL, **well_known = NULL;
-        const char *prefix, *color, *suffix;
-        int r;
+        const char *prefix, *color, *suffix, *s;
+        int r, q, v, w;
 
         assert(c);
 
@@ -362,8 +360,12 @@ int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
                 fprintf(f, "%sPID=%s"PID_FMT"%s", prefix, color, c->pid, suffix);
         if (c->mask & SD_BUS_CREDS_TID)
                 fprintf(f, "%sTID=%s"PID_FMT"%s", prefix, color, c->tid, suffix);
-        if (c->mask & SD_BUS_CREDS_PPID)
-                fprintf(f, "%sPPID=%s"PID_FMT"%s", prefix, color, c->ppid, suffix);
+        if (c->mask & SD_BUS_CREDS_PPID) {
+                if (c->ppid == 0)
+                        fprintf(f, "%sPPID=%sn/a%s", prefix, color, suffix);
+                else
+                        fprintf(f, "%sPPID=%s"PID_FMT"%s", prefix, color, c->ppid, suffix);
+        }
         if (c->mask & SD_BUS_CREDS_TTY)
                 fprintf(f, "%sTTY=%s%s%s", prefix, color, strna(c->tty), suffix);
 
@@ -409,12 +411,13 @@ int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
         if (c->mask & SD_BUS_CREDS_TID_COMM)
                 fprintf(f, "%sTIDComm=%s%s%s", prefix, color, c->tid_comm, suffix);
         if (c->mask & SD_BUS_CREDS_EXE)
-                fprintf(f, "%sExe=%s%s%s", prefix, color, c->exe, suffix);
+                fprintf(f, "%sExe=%s%s%s", prefix, color, strna(c->exe), suffix);
 
         if (terse && (c->mask & (SD_BUS_CREDS_EXE|SD_BUS_CREDS_COMM|SD_BUS_CREDS_TID_COMM)))
                 fputs("\n", f);
 
-        if (sd_bus_creds_get_cmdline(c, &cmdline) >= 0) {
+        r = sd_bus_creds_get_cmdline(c, &cmdline);
+        if (r >= 0) {
                 char **i;
 
                 fprintf(f, "%sCommandLine=%s", prefix, color);
@@ -426,7 +429,8 @@ int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
                 }
 
                 fprintf(f, "%s", suffix);
-        }
+        } else if (r != -ENODATA)
+                fprintf(f, "%sCommandLine=%sn/a%s", prefix, color, suffix);
 
         if (c->mask & SD_BUS_CREDS_SELINUX_CONTEXT)
                 fprintf(f, "%sLabel=%s%s%s", prefix, color, c->label, suffix);
@@ -438,32 +442,38 @@ int bus_creds_dump(sd_bus_creds *c, FILE *f, bool terse) {
 
         if (c->mask & SD_BUS_CREDS_CGROUP)
                 fprintf(f, "%sCGroup=%s%s%s", prefix, color, c->cgroup, suffix);
-        (void) sd_bus_creds_get_unit(c, &u);
-        if (u)
-                fprintf(f, "%sUnit=%s%s%s", prefix, color, u, suffix);
-        (void) sd_bus_creds_get_user_unit(c, &uu);
-        if (uu)
-                fprintf(f, "%sUserUnit=%s%s%s", prefix, color, uu, suffix);
-        (void) sd_bus_creds_get_slice(c, &sl);
-        if (sl)
-                fprintf(f, "%sSlice=%s%s%s", prefix, color, sl, suffix);
-        (void) sd_bus_creds_get_session(c, &s);
-        if (s)
-                fprintf(f, "%sSession=%s%s%s", prefix, color, s, suffix);
-
-        if (terse && ((c->mask & SD_BUS_CREDS_CGROUP) || u || uu || sl || s))
+        s = NULL;
+        r = sd_bus_creds_get_unit(c, &s);
+        if (r != -ENODATA)
+                fprintf(f, "%sUnit=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+        q = sd_bus_creds_get_user_unit(c, &s);
+        if (q != -ENODATA)
+                fprintf(f, "%sUserUnit=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+        v = sd_bus_creds_get_slice(c, &s);
+        if (v != -ENODATA)
+                fprintf(f, "%sSlice=%s%s%s", prefix, color, strna(s), suffix);
+        s = NULL;
+        w = sd_bus_creds_get_session(c, &s);
+        if (w != -ENODATA)
+                fprintf(f, "%sSession=%s%s%s", prefix, color, strna(s), suffix);
+
+        if (terse && ((c->mask & SD_BUS_CREDS_CGROUP) || r != -ENODATA || q != -ENODATA || v != -ENODATA || w != -ENODATA))
                 fputs("\n", f);
 
-        if (sd_bus_creds_get_audit_login_uid(c, &audit_loginuid) >= 0) {
-                audit_loginuid_is_set = true;
+        r = sd_bus_creds_get_audit_login_uid(c, &audit_loginuid);
+        if (r >= 0)
                 fprintf(f, "%sAuditLoginUID=%s"UID_FMT"%s", prefix, color, audit_loginuid, suffix);
-        }
-        if (sd_bus_creds_get_audit_session_id(c, &audit_sessionid) >= 0) {
-                audit_sessionid_is_set = true;
+        else if (r != -ENODATA)
+                fprintf(f, "%sAuditLoginUID=%sn/a%s", prefix, color, suffix);
+        q = sd_bus_creds_get_audit_session_id(c, &audit_sessionid);
+        if (q >= 0)
                 fprintf(f, "%sAuditSessionID=%s%"PRIu32"%s", prefix, color, audit_sessionid, suffix);
-        }
+        else if (q != -ENODATA)
+                fprintf(f, "%sAuditSessionID=%sn/a%s", prefix, color, suffix);
 
-        if (terse && (audit_loginuid_is_set || audit_sessionid_is_set))
+        if (terse && (r != -ENODATA || q != -ENODATA))
                 fputs("\n", f);
 
         if (c->mask & SD_BUS_CREDS_UNIQUE_NAME)