BUG/MINOR: mworker: Fix memory leak of mworker_proc members

The struct mworker_proc is not uniformly freed everywhere, sometimes leading
to leaks of the `id` string (and possibly the other strings).

Introduce a mworker_free_child function instead of duplicating the freeing
logic everywhere to prevent this kind of issues.

This leak was reported in issue #96.

It looks like the leaks have been introduced in commit 9a1ee7ac31c56fd7d881adf2ef4659f336e50c9f,
which is specific to 2.0-dev. Backporting `mworker_free_child` might be
helpful to ease backporting other fixes, though.

include/proto/mworker.h

@@ -36,4 +36,6 @@ int mworker_ext_launch_all();
 
 void mworker_kill_max_reloads(int sig);
 
+void mworker_free_child(struct mworker_proc *);
+
 #endif /* PROTO_MWORKER_H_ */

src/haproxy.c

@@ -3035,7 +3035,8 @@ int main(int argc, char **argv)
 					continue;
 				}
 				LIST_DEL(&child->list);
-				free(child);
+				mworker_free_child(child);
+				child = NULL;
 			}
 		}
 

src/mworker-prog.c

@@ -69,24 +69,7 @@ int mworker_ext_launch_all()
 
 
 				LIST_DEL(&child->list);
-				if (child->command) {
-					int i;
-
-					for (i = 0; child->command[i]; i++) {
-						if (child->command[i]) {
-							free(child->command[i]);
-							child->command[i] = NULL;
-						}
-					}
-					free(child->command);
-					child->command = NULL;
-				}
-				if (child->id) {
-					free(child->id);
-					child->id = NULL;
-				}
-
-				free(child);
+				mworker_free_child(child);
 				child = NULL;
 
 				continue;

src/mworker.c

@@ -185,9 +185,7 @@ void mworker_env_to_proc_list()
 
 			LIST_ADDQ(&proc_list, &child->list);
 		} else {
-			free(child->id);
-			free(child);
-
+			mworker_free_child(child);
 		}
 	}
 
@@ -245,7 +243,6 @@ void mworker_catch_sigchld(struct sig_handler *sh)
 {
 	int exitpid = -1;
 	int status = 0;
-	struct mworker_proc *child, *it;
 	int childfound;
 
 restart_wait:
@@ -254,6 +251,8 @@ restart_wait:
 
 	exitpid = waitpid(-1, &status, WNOHANG);
 	if (exitpid > 0) {
+		struct mworker_proc *child, *it;
+
 		if (WIFEXITED(status))
 			status = WEXITSTATUS(status);
 		else if (WIFSIGNALED(status))
@@ -301,7 +300,8 @@ restart_wait:
 					ha_warning("Former program '%s' (%d) exited with code %d (%s)\n", child->id, exitpid, status, (status >= 128) ? strsignal(status - 128) : "Exit");
 				}
 			}
-			free(child);
+			mworker_free_child(child);
+			child = NULL;
 		}
 
 		/* do it again to check if it was the last worker */
@@ -561,6 +561,29 @@ out:
 	return err_code;
 }
 
+void mworker_free_child(struct mworker_proc *child)
+{
+	if (child == NULL)
+		return;
+
+	if (child->command) {
+		int i;
+
+		for (i = 0; child->command[i]; i++) {
+			if (child->command[i]) {
+				free(child->command[i]);
+				child->command[i] = NULL;
+			}
+		}
+		free(child->command);
+		child->command = NULL;
+	}
+	if (child->id) {
+		free(child->id);
+		child->id = NULL;
+	}
+	free(child);
+}
 
 static struct cfg_kw_list mworker_kws = {{ }, {
 	{ CFG_GLOBAL, "mworker-max-reloads", mworker_parse_global_max_reloads },