app_macro: Prevent infinite loop in find_matching_priority.

Use AST_PBX_MAX_STACK to escape if we recurse 128 times.  This will
prevent crash if dialplan contains an include loop.  Log an error when
this occurs, at most one message per call to Macro() so we avoid logger
spam.

ASTERISK-26570 #close

Change-Id: I6c71b76998c31434391b150de055ae9a531e31da

apps/app_macro.c

@@ -37,6 +37,7 @@
 #include "asterisk/channel.h"
 #include "asterisk/pbx.h"
 #include "asterisk/module.h"
+#include "asterisk/extconf.h"
 #include "asterisk/config.h"
 #include "asterisk/utils.h"
 #include "asterisk/lock.h"
@@ -186,12 +187,21 @@ static void macro_fixup(void *data, struct ast_channel *old_chan, struct ast_cha
 	}
 }
 
-static struct ast_exten *find_matching_priority(struct ast_context *c, const char *exten, int priority, const char *callerid)
+static struct ast_exten *find_matching_priority(struct ast_context *c, const char *exten,
+	int priority, const char *callerid, int iter, int *had_error)
 {
 	struct ast_exten *e;
 	struct ast_context *c2;
 	int idx;
 
+	if (iter >= AST_PBX_MAX_STACK) {
+		if (!(*had_error)) {
+			*had_error = 1;
+			ast_log(LOG_ERROR, "Potential infinite loop detected, will not recurse further.\n");
+		}
+		return NULL;
+	}
+
 	for (e=ast_walk_context_extensions(c, NULL); e; e=ast_walk_context_extensions(c, e)) {
 		if (ast_extension_match(ast_get_extension_name(e), exten)) {
 			int needmatch = ast_get_extension_matchcid(e);
@@ -214,7 +224,7 @@ static struct ast_exten *find_matching_priority(struct ast_context *c, const cha
 
 		for (c2=ast_walk_contexts(NULL); c2; c2=ast_walk_contexts(c2)) {
 			if (!strcmp(ast_get_context_name(c2), ast_get_include_name(i))) {
-				e = find_matching_priority(c2, exten, priority, callerid);
+				e = find_matching_priority(c2, exten, priority, callerid, iter + 1, had_error);
 				if (e)
 					return e;
 			}
@@ -251,6 +261,7 @@ static int _macro_exec(struct ast_channel *chan, const char *data, int exclusive
 	char *save_macro_offset;
 	int save_in_subroutine;
 	struct ast_datastore *macro_store = ast_channel_datastore_find(chan, &macro_ds_info, NULL);
+	int had_infinite_include_error = 0;
 	static int deprecation_notice = 0;
 
 	if (ast_strlen_zero(data)) {
@@ -426,7 +437,9 @@ static int _macro_exec(struct ast_channel *chan, const char *data, int exclusive
 						ast_log(LOG_WARNING, "Unable to lock context?\n");
 					} else {
 						e = find_matching_priority(c, ast_channel_exten(chan), ast_channel_priority(chan),
-							S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, NULL));
+							S_COR(ast_channel_caller(chan)->id.number.valid,
+							ast_channel_caller(chan)->id.number.str, NULL),
+							0, &had_infinite_include_error);
 						if (e) { /* This will only be undefined for pbx_realtime, which is majorly broken. */
 							ast_copy_string(runningapp, ast_get_extension_app(e), sizeof(runningapp));
 							ast_copy_string(runningdata, ast_get_extension_app_data(e), sizeof(runningdata));