From 0e500d17bed8f5daf8e8640dd5c5594a7f39db21 Mon Sep 17 00:00:00 2001 From: Ilia Alshanetsky Date: Sat, 27 Jun 2026 17:33:33 -0400 Subject: [PATCH] Fix GH-22480: phpdbg use-after-free re-watching a watched variable phpdbg_add_watch_element() frees the passed element and returns the existing one when the variable is already watched, but several callers kept using the freed pointer, so re-watching a variable was a use-after-free in more places than the two reported. Report the duplicate back through the parse callback and register nothing, and reject a recursive watch's hashtable element that collides with an existing watch, at creation and recreation, rather than freeing a still-referenced one. A recursive watch over an already-array-watched variable now watches only the root and skips the shared hashtable. Running the tests under ASAN exposed a second, latent use-after-free at shutdown: the watch tables are module-scoped but hold request-pool memory, so under the tracked allocator freeing a watched variable during executor teardown re-queues an element after the last drain, tracked_free_all frees the pool, and phpdbg_destroy_watchpoints reads it at module shutdown. Tear the watch state down in a post_deactivate handler, which runs after the executor frees values but before the memory manager is torn down. Fixes GH-22480 --- NEWS | 4 + sapi/phpdbg/phpdbg.c | 11 +- sapi/phpdbg/phpdbg_watch.c | 209 +++++++++++++++++++++++++------ sapi/phpdbg/phpdbg_watch.h | 1 + sapi/phpdbg/tests/gh22480.phpt | 34 +++++ sapi/phpdbg/tests/gh22480_2.phpt | 30 +++++ sapi/phpdbg/tests/watch_006.phpt | 7 -- 7 files changed, 251 insertions(+), 45 deletions(-) create mode 100644 sapi/phpdbg/tests/gh22480.phpt create mode 100644 sapi/phpdbg/tests/gh22480_2.phpt diff --git a/NEWS b/NEWS index 9df461452c1c..7f6a84f3e3c6 100644 --- a/NEWS +++ b/NEWS @@ -184,6 +184,10 @@ PHP NEWS . Mark Phar::buildFromIterator() base directory argument as a path. (ndossche) +- phpdbg: + . Fixed GH-22480 (Use-after-free when re-watching an already-watched + variable). (iliaal) + - Posix: . Added validity check to the flags argument for posix_access(). (arshidkv12) diff --git a/sapi/phpdbg/phpdbg.c b/sapi/phpdbg/phpdbg.c index 3c0d5e836dd0..8cdc1aee9d48 100644 --- a/sapi/phpdbg/phpdbg.c +++ b/sapi/phpdbg/phpdbg.c @@ -239,6 +239,13 @@ static PHP_RSHUTDOWN_FUNCTION(phpdbg) /* {{{ */ return SUCCESS; } /* }}} */ +static ZEND_MODULE_POST_ZEND_DEACTIVATE_D(phpdbg) /* {{{ */ +{ + phpdbg_release_watch_elements(); + + return SUCCESS; +} /* }}} */ + /* {{{ Attempt to set the execution context for phpdbg If the execution context was set previously it is returned If the execution context was not set previously boolean true is returned @@ -681,7 +688,9 @@ static zend_module_entry sapi_phpdbg_module_entry = { PHP_RSHUTDOWN(phpdbg), NULL, PHPDBG_VERSION, - STANDARD_MODULE_PROPERTIES + NO_MODULE_GLOBALS, + ZEND_MODULE_POST_ZEND_DEACTIVATE_N(phpdbg), + STANDARD_MODULE_PROPERTIES_EX }; static inline int php_sapi_phpdbg_module_startup(sapi_module_struct *module) /* {{{ */ diff --git a/sapi/phpdbg/phpdbg_watch.c b/sapi/phpdbg/phpdbg_watch.c index b6d5e543a19c..f1eec989d0f7 100644 --- a/sapi/phpdbg/phpdbg_watch.c +++ b/sapi/phpdbg/phpdbg_watch.c @@ -501,8 +501,39 @@ void phpdbg_free_watch_element(phpdbg_watch_element *element); void phpdbg_remove_watchpoint(phpdbg_watchpoint_t *watch); void phpdbg_watch_parent_ht(phpdbg_watch_element *element); -phpdbg_watch_element *phpdbg_add_watch_element(phpdbg_watchpoint_t *watch, phpdbg_watch_element *element) { +static bool phpdbg_watch_element_collides(void *addr, phpdbg_watchtype type, phpdbg_watch_element *element) { + phpdbg_watch_element *old; + phpdbg_btree_result *res = phpdbg_btree_find(&PHPDBG_G(watchpoint_tree), (zend_ulong) addr); + + if (res) { + phpdbg_watchpoint_t *watch = res->ptr; + if (watch->type == type && (old = zend_hash_find_ptr(&watch->elements, element->str)) && old != element) { + return true; + } + } + + return (old = zend_hash_find_ptr(&PHPDBG_G(watch_recreation), element->str)) && old != element; +} + +static bool phpdbg_ht_watch_element_collides(zval *zv, phpdbg_watch_element *element) { + HashTable *ht = HT_FROM_ZVP(zv); + + if (!ht) { + return false; + } + + return phpdbg_watch_element_collides(HT_WATCH_OFFSET + (char *) ht, WATCH_ON_HASHTABLE, element); +} + +static bool phpdbg_bucket_watch_element_collides(zval *zv, phpdbg_watch_element *element) { + return phpdbg_watch_element_collides((Bucket *) zv, WATCH_ON_BUCKET, element); +} + +phpdbg_watch_element *phpdbg_add_watch_element(phpdbg_watchpoint_t *watch, phpdbg_watch_element *element, bool *is_new) { phpdbg_btree_result *res; + if (is_new) { + *is_new = true; + } if ((res = phpdbg_btree_find(&PHPDBG_G(watchpoint_tree), (zend_ulong) watch->addr.ptr)) == NULL) { phpdbg_watchpoint_t *mem = emalloc(sizeof(*mem)); *mem = *watch; @@ -520,6 +551,9 @@ phpdbg_watch_element *phpdbg_add_watch_element(phpdbg_watchpoint_t *watch, phpdb if (element != old_element) { phpdbg_free_watch_element(element); } + if (is_new) { + *is_new = false; + } return old_element; } } @@ -534,25 +568,35 @@ phpdbg_watch_element *phpdbg_add_watch_element(phpdbg_watchpoint_t *watch, phpdb return element; } -phpdbg_watch_element *phpdbg_add_bucket_watch_element(Bucket *bucket, phpdbg_watch_element *element) { +phpdbg_watch_element *phpdbg_add_bucket_watch_element(Bucket *bucket, phpdbg_watch_element *element, bool *is_new) { phpdbg_watchpoint_t watch; phpdbg_set_bucket_watchpoint(bucket, &watch); - element = phpdbg_add_watch_element(&watch, element); - phpdbg_watch_parent_ht(element); - return element; + bool added_new; + phpdbg_watch_element *added = phpdbg_add_watch_element(&watch, element, &added_new); + if (added_new) { + phpdbg_watch_parent_ht(added); + } + if (is_new) { + *is_new = added_new; + } + return added; } -phpdbg_watch_element *phpdbg_add_ht_watch_element(zval *zv, phpdbg_watch_element *element) { +phpdbg_watch_element *phpdbg_add_ht_watch_element(zval *zv, phpdbg_watch_element *element, bool *is_new) { phpdbg_watchpoint_t watch; HashTable *ht = HT_FROM_ZVP(zv); + if (is_new) { + *is_new = false; + } + if (!ht) { return NULL; } element->flags |= Z_TYPE_P(zv) == IS_ARRAY ? PHPDBG_WATCH_ARRAY : PHPDBG_WATCH_OBJECT; phpdbg_set_ht_watchpoint(ht, &watch); - return phpdbg_add_watch_element(&watch, element); + return phpdbg_add_watch_element(&watch, element, is_new); } bool phpdbg_is_recursively_watched(void *ptr, phpdbg_watch_element *element) { @@ -588,8 +632,15 @@ void phpdbg_add_recursive_watch_from_ht(phpdbg_watch_element *element, zend_long child->parent = element; child->child = NULL; child->parent_container = HT_WATCH_HT(element->watch); - zend_hash_add_ptr(&element->child_container, child->str, child); - phpdbg_add_bucket_watch_element((Bucket *) zv, child); + if (phpdbg_bucket_watch_element_collides(zv, child)) { + phpdbg_free_watch_element(child); + return; + } + bool added_new; + phpdbg_add_bucket_watch_element((Bucket *) zv, child, &added_new); + if (added_new) { + zend_hash_add_ptr(&element->child_container, child->str, child); + } } void phpdbg_recurse_watch_element(phpdbg_watch_element *element) { @@ -627,8 +678,13 @@ void phpdbg_recurse_watch_element(phpdbg_watch_element *element) { child->child = NULL; element->child = child; } + if (phpdbg_ht_watch_element_collides(zv, child)) { + phpdbg_free_watch_element(child); + element->child = NULL; + return; + } zend_hash_init(&child->child_container, 8, NULL, NULL, 0); - phpdbg_add_ht_watch_element(zv, child); + phpdbg_add_ht_watch_element(zv, child, NULL); } else if (zend_hash_num_elements(&element->child_container) == 0) { zend_string *str; zend_long idx; @@ -727,7 +783,10 @@ bool phpdbg_try_re_adding_watch_element(zval *parent, phpdbg_watch_element *elem phpdbg_print_watch_diff(WATCH_ON_HASHTABLE, element->str, oldPtr, htPtr); } - phpdbg_add_ht_watch_element(parent, element); + if ((element->flags & PHPDBG_WATCH_RECURSIVE) && phpdbg_ht_watch_element_collides(parent, element)) { + return false; + } + element = phpdbg_add_ht_watch_element(parent, element, NULL); } else if ((zv = zend_symtable_find(ht, element->name_in_parent))) { if (element->flags & PHPDBG_WATCH_IMPLICIT) { zval *next = zv; @@ -746,9 +805,11 @@ bool phpdbg_try_re_adding_watch_element(zval *parent, phpdbg_watch_element *elem phpdbg_print_watch_diff(WATCH_ON_ZVAL, element->str, &element->backup.zv, zv); } + if ((element->flags & PHPDBG_WATCH_RECURSIVE) && phpdbg_bucket_watch_element_collides(zv, element)) { + return false; + } element->parent_container = ht; - phpdbg_add_bucket_watch_element((Bucket *) zv, element); - phpdbg_watch_parent_ht(element); + element = phpdbg_add_bucket_watch_element((Bucket *) zv, element, NULL); } else { return false; } @@ -1248,49 +1309,80 @@ void phpdbg_list_watchpoints(void) { } ZEND_HASH_FOREACH_END(); } -static int phpdbg_create_simple_watchpoint(zval *zv, phpdbg_watch_element *element) { - element->flags = PHPDBG_WATCH_SIMPLE; - phpdbg_add_bucket_watch_element((Bucket *) zv, element); - return SUCCESS; +typedef enum { + PHPDBG_WATCH_ADD_OK, + PHPDBG_WATCH_ADD_FAILED, + PHPDBG_WATCH_ADD_DUPLICATE, +} phpdbg_watch_add_result; + +static phpdbg_watch_add_result phpdbg_create_simple_watchpoint(zval *zv, phpdbg_watch_element **element) { + phpdbg_watch_element *added; + (*element)->flags = PHPDBG_WATCH_SIMPLE; + bool added_new; + added = phpdbg_add_bucket_watch_element((Bucket *) zv, *element, &added_new); + if (!added_new) { + *element = added; + return PHPDBG_WATCH_ADD_DUPLICATE; + } + return PHPDBG_WATCH_ADD_OK; } -static int phpdbg_create_array_watchpoint(zval *zv, phpdbg_watch_element *element) { - phpdbg_watch_element *new; +static phpdbg_watch_add_result phpdbg_create_array_watchpoint(zval *zv, phpdbg_watch_element **element_ptr) { + phpdbg_watch_element *element = *element_ptr; + phpdbg_watch_element *new, *added; zend_string *str; zval *orig_zv = zv; ZVAL_DEREF(zv); if (Z_TYPE_P(zv) != IS_ARRAY && Z_TYPE_P(zv) != IS_OBJECT) { - return FAILURE; + return PHPDBG_WATCH_ADD_FAILED; } - new = ecalloc(1, sizeof(phpdbg_watch_element)); - str = strpprintf(0, "%.*s[]", (int) ZSTR_LEN(element->str), ZSTR_VAL(element->str)); zend_string_release(element->str); element->str = str; element->flags = PHPDBG_WATCH_IMPLICIT; - phpdbg_add_bucket_watch_element((Bucket *) orig_zv, element); - element->child = new; + bool added_new; + added = phpdbg_add_bucket_watch_element((Bucket *) orig_zv, element, &added_new); + if (!added_new) { + *element_ptr = added; + return PHPDBG_WATCH_ADD_DUPLICATE; + } + element = added; + new = ecalloc(1, sizeof(phpdbg_watch_element)); new->flags = PHPDBG_WATCH_SIMPLE; new->str = zend_string_copy(str); new->parent = element; - phpdbg_add_ht_watch_element(zv, new); - return SUCCESS; + added = phpdbg_add_ht_watch_element(zv, new, &added_new); + if (added != NULL && !added_new) { + phpdbg_clean_watch_element(element); + phpdbg_free_watch_element(element); + *element_ptr = added; + return PHPDBG_WATCH_ADD_DUPLICATE; + } + element->child = new; + *element_ptr = element; + return PHPDBG_WATCH_ADD_OK; } -static int phpdbg_create_recursive_watchpoint(zval *zv, phpdbg_watch_element *element) { - element->flags = PHPDBG_WATCH_RECURSIVE | PHPDBG_WATCH_RECURSIVE_ROOT; - element->child = NULL; - phpdbg_add_bucket_watch_element((Bucket *) zv, element); - return SUCCESS; +static phpdbg_watch_add_result phpdbg_create_recursive_watchpoint(zval *zv, phpdbg_watch_element **element) { + phpdbg_watch_element *added; + (*element)->flags = PHPDBG_WATCH_RECURSIVE | PHPDBG_WATCH_RECURSIVE_ROOT; + (*element)->child = NULL; + bool added_new; + added = phpdbg_add_bucket_watch_element((Bucket *) zv, *element, &added_new); + if (!added_new) { + *element = added; + return PHPDBG_WATCH_ADD_DUPLICATE; + } + return PHPDBG_WATCH_ADD_OK; } -typedef struct { int (*callback)(zval *zv, phpdbg_watch_element *); zend_string *str; } phpdbg_watch_parse_struct; +typedef struct { phpdbg_watch_add_result (*callback)(zval *zv, phpdbg_watch_element **); zend_string *str; } phpdbg_watch_parse_struct; static int phpdbg_watchpoint_parse_wrapper(char *name, size_t namelen, char *key, size_t keylen, HashTable *parent, zval *zv, phpdbg_watch_parse_struct *info) { - int ret; + int ret = SUCCESS; phpdbg_watch_element *element = ecalloc(1, sizeof(phpdbg_watch_element)); element->str = zend_string_init(name, namelen, 0); element->name_in_parent = zend_string_init(key, keylen, 0); @@ -1298,13 +1390,25 @@ static int phpdbg_watchpoint_parse_wrapper(char *name, size_t namelen, char *key element->parent = PHPDBG_G(watch_tmp); element->child = NULL; - ret = info->callback(zv, element); + phpdbg_watch_add_result result = info->callback(zv, &element); efree(name); efree(key); - if (ret != SUCCESS) { + if (result == PHPDBG_WATCH_ADD_FAILED) { phpdbg_remove_watch_element(element); + ret = FAILURE; + } else if (result == PHPDBG_WATCH_ADD_DUPLICATE) { + phpdbg_notice("%.*s is already being watched", (int) ZSTR_LEN(element->str), ZSTR_VAL(element->str)); + while (PHPDBG_G(watch_tmp) && PHPDBG_G(watch_tmp)->child == NULL) { + phpdbg_watch_element *parent = PHPDBG_G(watch_tmp)->parent; + phpdbg_clean_watch_element(PHPDBG_G(watch_tmp)); + phpdbg_free_watch_element(PHPDBG_G(watch_tmp)); + if (parent) { + parent->child = NULL; + } + PHPDBG_G(watch_tmp) = parent; + } } else { if (PHPDBG_G(watch_tmp)) { PHPDBG_G(watch_tmp)->child = element; @@ -1346,7 +1450,7 @@ static int phpdbg_watchpoint_parse_step(char *name, size_t namelen, char *key, s element->name_in_parent = zend_string_init(key, keylen, 0); element->parent_container = parent; element->parent = PHPDBG_G(watch_tmp); - element = phpdbg_add_bucket_watch_element((Bucket *) zv, element); + element = phpdbg_add_bucket_watch_element((Bucket *) zv, element, NULL); efree(name); efree(key); @@ -1359,7 +1463,7 @@ static int phpdbg_watchpoint_parse_step(char *name, size_t namelen, char *key, s return SUCCESS; } -static int phpdbg_watchpoint_parse_symtables(char *input, size_t len, int (*callback)(zval *, phpdbg_watch_element *)) { +static int phpdbg_watchpoint_parse_symtables(char *input, size_t len, phpdbg_watch_add_result (*callback)(zval *, phpdbg_watch_element **)) { zend_class_entry *scope = zend_get_executed_scope(); phpdbg_watch_parse_struct info; int ret; @@ -1529,6 +1633,37 @@ void phpdbg_destroy_watchpoints(void) { free(PHPDBG_G(watchlist_mem_backup)); } +void phpdbg_release_watch_elements(void) { + phpdbg_watch_element *element; + uint32_t guard; + + ZEND_HASH_MAP_FOREACH_PTR(&PHPDBG_G(watch_recreation), element) { + phpdbg_automatic_dequeue_free(element); + } ZEND_HASH_FOREACH_END(); + zend_hash_clean(&PHPDBG_G(watch_recreation)); + + guard = zend_hash_num_elements(&PHPDBG_G(watch_elements)) + 1; + while (zend_hash_num_elements(&PHPDBG_G(watch_elements)) > 0 && guard-- > 0) { + ZEND_HASH_FOREACH_PTR(&PHPDBG_G(watch_elements), element) { + phpdbg_remove_watch_element(element); + break; + } ZEND_HASH_FOREACH_END(); + } + zend_hash_clean(&PHPDBG_G(watch_recreation)); + + phpdbg_btree_clean(&PHPDBG_G(watchpoint_tree)); + phpdbg_btree_clean(&PHPDBG_G(watch_HashTables)); + + zend_hash_destroy(&PHPDBG_G(watch_elements)); + zend_hash_init(&PHPDBG_G(watch_elements), 8, NULL, NULL, 0); + zend_hash_destroy(&PHPDBG_G(watch_recreation)); + zend_hash_init(&PHPDBG_G(watch_recreation), 8, NULL, NULL, 0); + zend_hash_destroy(&PHPDBG_G(watch_free)); + zend_hash_init(&PHPDBG_G(watch_free), 8, NULL, NULL, 0); + zend_hash_destroy(&PHPDBG_G(watch_collisions)); + zend_hash_init(&PHPDBG_G(watch_collisions), 8, NULL, NULL, 0); +} + void phpdbg_purge_watchpoint_tree(void) { phpdbg_btree_position pos; phpdbg_btree_result *res; diff --git a/sapi/phpdbg/phpdbg_watch.h b/sapi/phpdbg/phpdbg_watch.h index 380140fd9f1f..e87dd77f0543 100644 --- a/sapi/phpdbg/phpdbg_watch.h +++ b/sapi/phpdbg/phpdbg_watch.h @@ -110,6 +110,7 @@ typedef struct { void phpdbg_setup_watchpoints(void); void phpdbg_destroy_watchpoints(void); +void phpdbg_release_watch_elements(void); void phpdbg_purge_watchpoint_tree(void); #ifndef _WIN32 diff --git a/sapi/phpdbg/tests/gh22480.phpt b/sapi/phpdbg/tests/gh22480.phpt new file mode 100644 index 000000000000..16559a75f27a --- /dev/null +++ b/sapi/phpdbg/tests/gh22480.phpt @@ -0,0 +1,34 @@ +--TEST-- +GH-22480 (Use-after-free when re-watching an already-watched variable) +--PHPDBG-- +b 6 +r +w a $a +w a $a +c + +q +--EXPECTF-- +[Successful compilation of %s] +prompt> [Breakpoint #0 added at %s:6] +prompt> [Breakpoint #0 at %s:6, hits: 1] +>00006: $a[0] = 2; + 00007: + 00008: $a = [0 => 3, 1 => 4]; +prompt> [Added watchpoint #0 for $a[]] +prompt> [$a[] is already being watched] +prompt> [Breaking on watchpoint $a[]] +1 elements were added to the array +>00009: +prompt> [$a[] has been removed, removing watchpoint] +[Script ended normally] +prompt> +--FILE-- + 3, 1 => 4]; diff --git a/sapi/phpdbg/tests/gh22480_2.phpt b/sapi/phpdbg/tests/gh22480_2.phpt new file mode 100644 index 000000000000..aa6e13dbf8d5 --- /dev/null +++ b/sapi/phpdbg/tests/gh22480_2.phpt @@ -0,0 +1,30 @@ +--TEST-- +GH-22480 (Use-after-free re-watching a sub-path of a recursive watchpoint) +--INI-- +opcache.optimization_level=0 +--PHPDBG-- +b 5 +r +w r $a +w $a[x] +c +q +--EXPECTF-- +[Successful compilation of %s] +prompt> [Breakpoint #0 added at %s:5] +prompt> [Breakpoint #0 at %s:5, hits: 1] +>00005: $a['x'] = 2; + 00006: +prompt> [Added watchpoint #0 for $a[]] +prompt> [$a[x] is already being watched] +prompt> [Breaking on watchpoint $a] +Old value%s +New value: Array ([x] => 2) +>00006: +prompt> [$a has been removed, removing watchpoint recursively] +--FILE-- + 1]; + +$a['x'] = 2; diff --git a/sapi/phpdbg/tests/watch_006.phpt b/sapi/phpdbg/tests/watch_006.phpt index c5f53a37510c..bf38b8eff1fb 100644 --- a/sapi/phpdbg/tests/watch_006.phpt +++ b/sapi/phpdbg/tests/watch_006.phpt @@ -1,12 +1,5 @@ --TEST-- Test multiple watch elements pointing to the same watchpoint ---SKIPIF-- - --PHPDBG-- b 4 r