Fix GH-13681: segfault when adding watchpoint fails.

thus when removing its entry, no watch point is set and crash on
pointer access.

close GH-14513

NEWS

@@ -46,6 +46,9 @@ PHP                                                                        NEWS
 - PDO ODBC:
   . Fixed bug GH-14367 (incompatible SDWORD type with iODBC). (Calvin Buckley)
 
+- PHPDBG:
+  . Fixed bug GH-13681 (segfault on watchpoint addition failure). (David Carlier)
+
 - Soap:
   . Fixed bug #47925 (PHPClient can't decompress response). (nielsdos)
   . Fix missing error restore code. (nielsdos)

sapi/phpdbg/phpdbg_watch.c

@@ -315,7 +315,7 @@ void *phpdbg_watchpoint_userfaultfd_thread(void *phpdbg_globals) {
 
 	struct uffd_msg fault_msg = {0};
 	while (read(globals->watch_userfaultfd, &fault_msg, sizeof(fault_msg)) == sizeof(fault_msg)) {
-    	void *page = phpdbg_get_page_boundary((char *)(uintptr_t) fault_msg.arg.pagefault.address);
+		void *page = phpdbg_get_page_boundary((char *)(uintptr_t) fault_msg.arg.pagefault.address);
 		zend_hash_index_add_empty_element(globals->watchlist_mem, (zend_ulong) page);
 		struct uffdio_writeprotect unprotect = {
 			.mode = 0,
@@ -668,7 +668,7 @@ void phpdbg_watch_parent_ht(phpdbg_watch_element *element) {
 }
 
 void phpdbg_unwatch_parent_ht(phpdbg_watch_element *element) {
-	if (element->watch->type == WATCH_ON_BUCKET) {
+	if (element->watch && element->watch->type == WATCH_ON_BUCKET) {
 		phpdbg_btree_result *res = phpdbg_btree_find(&PHPDBG_G(watch_HashTables), (zend_ulong) element->parent_container);
 		ZEND_ASSERT(element->parent_container);
 		if (res) {
@@ -969,11 +969,14 @@ void phpdbg_remove_watchpoint(phpdbg_watchpoint_t *watch) {
 }
 
 void phpdbg_clean_watch_element(phpdbg_watch_element *element) {
-	HashTable *elements = &element->watch->elements;
 	phpdbg_unwatch_parent_ht(element);
-	zend_hash_del(elements, element->str);
-	if (zend_hash_num_elements(elements) == 0) {
-		phpdbg_remove_watchpoint(element->watch);
+
+	if (element->watch) {
+		HashTable *elements = &element->watch->elements;
+		zend_hash_del(elements, element->str);
+		if (zend_hash_num_elements(elements) == 0) {
+			phpdbg_remove_watchpoint(element->watch);
+		}
 	}
 }
 

sapi/phpdbg/tests/gh13681.phpt

@@ -0,0 +1,39 @@
+--TEST--
+phpdbg_watch null pointer access
+--CREDITS--
+Yuancheng Jiang
+--SKIPIF--
+<?php
+if (getenv('SKIP_ASAN')) {
+    die("skip intentionally causes segfaults");
+}
+?>
+--FILE--
+<?php
+echo "*** Testing array_multisort() : Testing with anonymous arguments ***\n";
+var_dump(array_multisort(array(1,3,2,4)));
+$xconnect=$GLOBALS[array_rand($GLOBALS)];
+echo "Done\n";
+$a = [];
+$a[0] = 1;
+$a[0] = 2;
+$a = [0 => 3, 1 => 4];
+?>
+--PHPDBG--
+b 6
+r
+w a $a
+c
+q
+--EXPECTF--
+[Successful compilation of %s]
+prompt> [Breakpoint #0 added at %s:%d]
+prompt> *** Testing array_multisort() : Testing with anonymous arguments ***
+bool(true)
+Done
+[Breakpoint #0 at %s:%d, hits: 1]
+>00006: $a = [];
+ 00007: $a[0] = 1;
+ 00008: $a[0] = 2;
+prompt> prompt> [Script ended normally]
+prompt>