core: Fix assertion with empty Exec*= paths

An Exec*= line with whitespace after modifiers, like

  ExecStart=- /bin/true

is considered to have an empty command path. This is as specified, but causes
systemd to crash with

  Assertion 'skip < l' failed at ../src/core/load-fragment.c:607, function config_parse_exec(). Aborting.
  Aborted (core dumped)

Fix this by logging an error instead and ignoring the invalid line.

Add corresponding test cases. Also add a test case for a completely empty value
which resets the command list.

https://launchpad.net/bugs/1454173

1 files changed, 21 insertions, 0 deletions

diff --git a/src/test/test-unit-file.c b/src/test/test-unit-file.c
index f3f6c29f75..03ca70a493 100644
--- a/src/test/test-unit-file.c
+++ b/src/test/test-unit-file.c
@@ -317,6 +317,27 @@ static void test_config_parse_exec(void) {
         assert_se(r == 0);
         assert_se(c1->command_next == NULL);
 
+        log_info("/* invalid space between modifiers */");
+        r = config_parse_exec(NULL, "fake", 4, "section", 1,
+                              "LValue", 0, "- /path",
+                              &c, NULL);
+        assert_se(r == 0);
+        assert_se(c1->command_next == NULL);
+
+        log_info("/* only modifiers, no path */");
+        r = config_parse_exec(NULL, "fake", 4, "section", 1,
+                              "LValue", 0, "-",
+                              &c, NULL);
+        assert_se(r == 0);
+        assert_se(c1->command_next == NULL);
+
+        log_info("/* empty argument, reset */");
+        r = config_parse_exec(NULL, "fake", 4, "section", 1,
+                              "LValue", 0, "",
+                              &c, NULL);
+        assert_se(r == 0);
+        assert_se(c == NULL);
+
         exec_command_free_list(c);
 }