basic/log: log any available location information in log_syntax()

We would log "(null):0: Failed to parse system call, ignoring: rseq" from
log_syntax_internal() from log_syntax() from seccomp_parse_syscall_filter_full()
from seccomp_parse_syscall_filter() from config_parse_syscall_filter(),
when generating the built-in @default whitelist. Since it was not based on the
unit file, we would not pass a file name.

So let's make sure that log_syntax() does not print "(null)" pointer (which is
iffy and ugly), and use the unit name as fallback or nothing if both are missing.
In principle, one of the two should be always available, since why use log_syntax()
otherwise, but let's make things more resilient by guarding against this case too.
log_syntax() is called from a thousand places, and often in error path, so it's
hard to verify all callers.

diff --git a/src/basic/log.c b/src/basic/log.c
index 37a5ffa74f9df9747b0cf24291e2902719f0a5ce..ea252c41302fb6fd9d0b29d9853a3c9f9a760f2d 100644 (file)
--- a/src/basic/log.c
+++ b/src/basic/log.c
@@ -1231,16 +1231,34 @@ int log_syntax_internal(
         if (unit)
                 unit_fmt = getpid_cached() == 1 ? "UNIT=%s" : "USER_UNIT=%s";
 
-        return log_struct_internal(
-                        LOG_REALM_PLUS_LEVEL(LOG_REALM_SYSTEMD, level),
-                        error,
-                        file, line, func,
-                        "MESSAGE_ID=" SD_MESSAGE_INVALID_CONFIGURATION_STR,
-                        "CONFIG_FILE=%s", config_file,
-                        "CONFIG_LINE=%u", config_line,
-                        LOG_MESSAGE("%s:%u: %s", config_file, config_line, buffer),
-                        unit_fmt, unit,
-                        NULL);
+        if (config_file)
+                return log_struct_internal(
+                                LOG_REALM_PLUS_LEVEL(LOG_REALM_SYSTEMD, level),
+                                error,
+                                file, line, func,
+                                "MESSAGE_ID=" SD_MESSAGE_INVALID_CONFIGURATION_STR,
+                                "CONFIG_FILE=%s", config_file,
+                                "CONFIG_LINE=%u", config_line,
+                                LOG_MESSAGE("%s:%u: %s", config_file, config_line, buffer),
+                                unit_fmt, unit,
+                                NULL);
+        else if (unit)
+                return log_struct_internal(
+                                LOG_REALM_PLUS_LEVEL(LOG_REALM_SYSTEMD, level),
+                                error,
+                                file, line, func,
+                                "MESSAGE_ID=" SD_MESSAGE_INVALID_CONFIGURATION_STR,
+                                LOG_MESSAGE("%s: %s", unit, buffer),
+                                unit_fmt, unit,
+                                NULL);
+        else
+                return log_struct_internal(
+                                LOG_REALM_PLUS_LEVEL(LOG_REALM_SYSTEMD, level),
+                                error,
+                                file, line, func,
+                                "MESSAGE_ID=" SD_MESSAGE_INVALID_CONFIGURATION_STR,
+                                LOG_MESSAGE("%s", buffer),
+                                NULL);
 }
 
 int log_syntax_invalid_utf8_internal(