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Fix GH-21831: Disallow SplObjectStorage mutation during getHash() #21835

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Fix GH-21831: Disallow SplObjectStorage mutation during getHash() #21835

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2 changes: 2 additions & 0 deletions NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -151,6 +151,8 @@ PHP NEWS
- SPL:
. DirectoryIterator key can now work better with filesystem supporting larger
directory indexing. (David Carlier)
. Fixed bug GH-21831 (SplObjectStorage::removeAllExcept() use-after-free
with re-entrant getHash()). (Pratik Bhujel)
. Fix bugs GH-8561, GH-8562, GH-8563, and GH-8564 (Fixing various
SplFileObject iterator desync bugs). (iliaal)

Expand Down
2 changes: 2 additions & 0 deletions UPGRADING
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,8 @@ PHP 8.6 UPGRADE NOTES
logic in their updateTimestamp() method.

- SPL:
. SplObjectStorage::getHash() implementations may no longer mutate any
SplObjectStorage instance. Attempting to do so now throws an Error.
. SplFileObject::next() now advances the stream when no prior current()
call has cached a line. A subsequent current() call returns the new
line rather than the previous one.
Expand Down
111 changes: 104 additions & 7 deletions ext/spl/spl_observer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,8 @@ static zend_object_handlers spl_handler_MultipleIterator;
#define SOS_OVERRIDDEN_WRITE_DIMENSION 2
#define SOS_OVERRIDDEN_UNSET_DIMENSION 4

ZEND_TLS uint32_t spl_object_storage_get_hash_depth;

typedef struct _spl_SplObjectStorage { /* {{{ */
HashTable storage;
zend_long index;
Expand All @@ -69,6 +71,16 @@ static inline spl_SplObjectStorage *spl_object_storage_from_obj(zend_object *obj

#define Z_SPLOBJSTORAGE_P(zv) spl_object_storage_from_obj(Z_OBJ_P((zv)))

static zend_always_inline bool spl_object_storage_disallow_mutation_during_get_hash(void)
{
if (UNEXPECTED(spl_object_storage_get_hash_depth)) {
zend_throw_error(NULL, "Modification of SplObjectStorage during getHash() is prohibited");
return true;
}

return false;
}

static void spl_SplObjectStorage_free_storage(zend_object *object) /* {{{ */
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
Expand All @@ -83,7 +95,10 @@ static zend_result spl_object_storage_get_hash(zend_hash_key *key, spl_SplObject
zval param;
zval rv;
ZVAL_OBJ(&param, obj);
ZVAL_UNDEF(&rv);
spl_object_storage_get_hash_depth++;
zend_call_method_with_1_params(&intern->std, intern->std.ce, &intern->fptr_get_hash, "getHash", &rv, &param);
spl_object_storage_get_hash_depth--;
if (UNEXPECTED(Z_ISUNDEF(rv))) {
/* An exception has occurred */
return FAILURE;
Expand Down Expand Up @@ -176,6 +191,10 @@ static spl_SplObjectStorageElement *spl_object_storage_attach_handle(spl_SplObje

static spl_SplObjectStorageElement *spl_object_storage_attach(spl_SplObjectStorage *intern, zend_object *obj, zval *inf) /* {{{ */
{
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
return NULL;
}

if (EXPECTED(!(intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION))) {
return spl_object_storage_attach_handle(intern, obj, inf);
}
Expand Down Expand Up @@ -221,6 +240,10 @@ static spl_SplObjectStorageElement *spl_object_storage_attach(spl_SplObjectStora

static zend_result spl_object_storage_detach(spl_SplObjectStorage *intern, zend_object *obj) /* {{{ */
{
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
return FAILURE;
}

if (EXPECTED(!(intern->flags & SOS_OVERRIDDEN_UNSET_DIMENSION))) {
return zend_hash_index_del(&intern->storage, obj->handle);
}
Expand All @@ -247,20 +270,25 @@ static zend_result spl_object_storage_detach(spl_SplObjectStorage *intern, zend_
if (UNEXPECTED(Z_ISUNDEF_P(_z))) continue; \
_ptr = Z_PTR_P(_z);

static void spl_object_storage_addall(spl_SplObjectStorage *intern, spl_SplObjectStorage *other) { /* {{{ */
static zend_result spl_object_storage_addall(spl_SplObjectStorage *intern, spl_SplObjectStorage *other) { /* {{{ */
spl_SplObjectStorageElement *element;

SPL_SAFE_HASH_FOREACH_PTR(&other->storage, element) {
zval zv;
zend_object *obj = element->obj;
GC_ADDREF(obj);
ZVAL_COPY(&zv, &element->inf);
spl_object_storage_attach(intern, obj, &zv);
if (UNEXPECTED(!spl_object_storage_attach(intern, obj, &zv))) {
zval_ptr_dtor(&zv);
OBJ_RELEASE(obj);
return FAILURE;
}
zval_ptr_dtor(&zv);
OBJ_RELEASE(obj);
} ZEND_HASH_FOREACH_END();

intern->index = 0;
return SUCCESS;
} /* }}} */

#define SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, zstr_method) \
Expand Down Expand Up @@ -446,6 +474,9 @@ PHP_METHOD(SplObjectStorage, attach)
Z_PARAM_ZVAL(inf)
ZEND_PARSE_PARAMETERS_END();
spl_object_storage_attach(intern, obj, inf);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
} /* }}} */

// todo: make spl_object_storage_has_dimension return bool as well
Expand Down Expand Up @@ -494,6 +525,10 @@ static zval *spl_object_storage_read_dimension(zend_object *object, zval *offset
static void spl_object_storage_write_dimension(zend_object *object, zval *offset, zval *inf)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
return;
}

if (UNEXPECTED(offset == NULL || Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION))) {
zend_std_write_dimension(object, offset, inf);
return;
Expand All @@ -504,6 +539,10 @@ static void spl_object_storage_write_dimension(zend_object *object, zval *offset
static void spl_multiple_iterator_write_dimension(zend_object *object, zval *offset, zval *inf)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
return;
}

if (UNEXPECTED(offset == NULL || Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION))) {
zend_std_write_dimension(object, offset, inf);
return;
Expand All @@ -518,6 +557,10 @@ static void spl_multiple_iterator_write_dimension(zend_object *object, zval *off
static void spl_object_storage_unset_dimension(zend_object *object, zval *offset)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
return;
}

if (UNEXPECTED(Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_UNSET_DIMENSION))) {
zend_std_unset_dimension(object, offset);
return;
Expand All @@ -535,6 +578,9 @@ PHP_METHOD(SplObjectStorage, detach)
Z_PARAM_OBJ(obj)
ZEND_PARSE_PARAMETERS_END();
spl_object_storage_detach(intern, obj);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}

zend_hash_internal_pointer_reset_ex(&intern->storage, &intern->pos);
intern->index = 0;
Expand Down Expand Up @@ -566,6 +612,9 @@ PHP_METHOD(SplObjectStorage, offsetGet)
ZEND_PARSE_PARAMETERS_END();

if (spl_object_storage_get_hash(&key, intern, obj) == FAILURE) {
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
RETURN_NULL();
}

Expand All @@ -592,7 +641,9 @@ PHP_METHOD(SplObjectStorage, addAll)

other = Z_SPLOBJSTORAGE_P(obj);

spl_object_storage_addall(intern, other);
if (UNEXPECTED(spl_object_storage_addall(intern, other) == FAILURE)) {
RETURN_THROWS();
}

RETURN_LONG(zend_hash_num_elements(&intern->storage));
} /* }}} */
Expand All @@ -614,6 +665,9 @@ PHP_METHOD(SplObjectStorage, removeAll)
zend_hash_internal_pointer_reset(&other->storage);
while ((element = zend_hash_get_current_data_ptr(&other->storage)) != NULL) {
if (spl_object_storage_detach(intern, element->obj) == FAILURE) {
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
zend_hash_move_forward(&other->storage);
}
}
Expand Down Expand Up @@ -641,8 +695,19 @@ PHP_METHOD(SplObjectStorage, removeAllExcept)
SPL_SAFE_HASH_FOREACH_PTR(&intern->storage, element) {
zend_object *elem_obj = element->obj;
GC_ADDREF(elem_obj);
if (!spl_object_storage_contains(other, elem_obj)) {
spl_object_storage_detach(intern, elem_obj);
bool contains = spl_object_storage_contains(other, elem_obj);
if (UNEXPECTED(EG(exception))) {
OBJ_RELEASE(elem_obj);
RETURN_THROWS();
}
if (!contains) {
if (spl_object_storage_detach(intern, elem_obj) == FAILURE) {
OBJ_RELEASE(elem_obj);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
continue;
}
}
OBJ_RELEASE(elem_obj);
} ZEND_HASH_FOREACH_END();
Expand All @@ -663,7 +728,13 @@ PHP_METHOD(SplObjectStorage, contains)
ZEND_PARSE_PARAMETERS_START(1, 1)
Z_PARAM_OBJ(obj)
ZEND_PARSE_PARAMETERS_END();
RETURN_BOOL(spl_object_storage_contains(intern, obj));

bool contains = spl_object_storage_contains(intern, obj);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}

RETURN_BOOL(contains);
} /* }}} */

/* {{{ Determine number of objects in storage */
Expand Down Expand Up @@ -753,6 +824,9 @@ PHP_METHOD(SplObjectStorage, setInfo)
if (zend_parse_parameters(ZEND_NUM_ARGS(), "z", &inf) == FAILURE) {
RETURN_THROWS();
}
if (UNEXPECTED(spl_object_storage_disallow_mutation_during_get_hash())) {
RETURN_THROWS();
}

if ((element = zend_hash_get_current_data_ptr_ex(&intern->storage, &intern->pos)) == NULL) {
RETURN_NULL();
Expand Down Expand Up @@ -947,6 +1021,10 @@ PHP_METHOD(SplObjectStorage, unserialize)

if (spl_object_storage_get_hash(&key, intern, Z_OBJ_P(entry)) == FAILURE) {
zval_ptr_dtor(&inf);
if (EG(exception)) {
PHP_VAR_UNSERIALIZE_DESTROY(var_hash);
RETURN_THROWS();
}
goto outexcept;
}
pelement = spl_object_storage_get(intern, &key);
Expand All @@ -960,6 +1038,14 @@ PHP_METHOD(SplObjectStorage, unserialize)
var_push_dtor(&var_hash, &obj);
}
element = spl_object_storage_attach(intern, Z_OBJ_P(entry), Z_ISUNDEF(inf)?NULL:&inf);
if (UNEXPECTED(!element)) {
zval_ptr_dtor(&inf);
if (EG(exception)) {
PHP_VAR_UNSERIALIZE_DESTROY(var_hash);
RETURN_THROWS();
}
goto outexcept;
}
var_replace(&var_hash, &inf, &element->inf);
zval_ptr_dtor(&inf);
}
Expand Down Expand Up @@ -1055,7 +1141,9 @@ PHP_METHOD(SplObjectStorage, __unserialize)
}

ZVAL_DEREF(val);
spl_object_storage_attach(intern, Z_OBJ_P(key), val);
if (UNEXPECTED(!spl_object_storage_attach(intern, Z_OBJ_P(key), val))) {
RETURN_THROWS();
}
key = NULL;
} else {
key = val;
Expand Down Expand Up @@ -1151,8 +1239,14 @@ PHP_METHOD(MultipleIterator, attachIterator)
}

spl_object_storage_attach(intern, iterator, &zinfo);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
} else {
spl_object_storage_attach(intern, iterator, NULL);
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}
}
}
/* }}} */
Expand All @@ -1167,6 +1261,9 @@ PHP_METHOD(MultipleIterator, detachIterator)
RETURN_THROWS();
}
spl_object_storage_detach(intern, Z_OBJ_P(iterator));
if (UNEXPECTED(EG(exception))) {
RETURN_THROWS();
}

zend_hash_internal_pointer_reset_ex(&intern->storage, &intern->pos);
intern->index = 0;
Expand Down
54 changes: 35 additions & 19 deletions ext/spl/tests/SplObjectStorage/concurrent_deletion.phpt
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Original file line number Diff line number Diff line change
@@ -1,46 +1,62 @@
--TEST--
SplObjectStorage: Concurrent deletion during iteration
SplObjectStorage: Mutation during getHash is prohibited
--CREDITS--
cnitlrt
--FILE--
<?php
class EvilStorage extends SplObjectStorage {
public bool $mutate = false;

public function getHash($obj): string {
global $victim;
static $counter = 0;
if ($counter++ < 1024*2) {
// Re-entrant mutation during removeAllExcept iteration
for ($i = 0; $i < 5; $i++) {
$victim[new stdClass()] = null;
}
if ($this->mutate) {
$victim[new stdClass()] = null;
}
return spl_object_hash($obj);
}
}

function populate(SplObjectStorage $victim, SplObjectStorage $other): void {
for ($i = 0; $i < 1024; $i++) {
$o = new stdClass();
$victim[$o] = null;
$other[$o] = null;
}
}

$victim = new SplObjectStorage();
$other = new EvilStorage();

for ($i = 0; $i < 1024; $i++) {
$o = new stdClass();
$victim[$o] = null;
$other[$o] = null;
populate($victim, $other);
$other->mutate = true;

try {
$victim->removeAllExcept($other);
} catch (Error $e) {
echo $e->getMessage(), "\n";
}

var_dump($victim->removeAllExcept($other));
var_dump(count($victim), count($other));

unset($victim, $other);
$victim = new SplObjectStorage();
$other = new EvilStorage();

for ($i = 0; $i < 1024; $i++) {
$o = new stdClass();
$victim[$o] = null;
$other[$o] = null;
populate($victim, $other);
$other->mutate = true;

try {
$other->addAll($victim);
} catch (Error $e) {
echo $e->getMessage(), "\n";
}

var_dump($other->addAll($victim));
var_dump(count($victim), count($other));
?>
--EXPECTF--
int(%d)
--EXPECT--
Modification of SplObjectStorage during getHash() is prohibited
int(1024)
int(1024)
Modification of SplObjectStorage during getHash() is prohibited
int(1024)
int(1024)
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