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Fix GH-16414: zend_test.observer.observe_function_names may segfault #16438

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Fix GH-16414: zend_test.observer.observe_function_names may segfault #16438

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37396ab
Fix GH-16414: zend_test.observer.observe_function_names may segfault
cmb69 Oct 14, 2024
3d4f8e9
Must not have zend_test.observer.enabled
cmb69 Oct 14, 2024
8719baa
Ensure that the functions have already been called
cmb69 Oct 16, 2024
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7 changes: 5 additions & 2 deletions ext/zend_test/observer.c
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Expand Up @@ -304,9 +304,12 @@ static ZEND_INI_MH(zend_test_observer_OnUpdateCommaList)
zend_array **p = (zend_array **) ZEND_INI_GET_ADDR();
zend_string *funcname;
zend_function *func;
if (!ZT_G(observer_enabled)) {
return FAILURE;
}
if (stage != PHP_INI_STAGE_STARTUP && stage != PHP_INI_STAGE_ACTIVATE && stage != PHP_INI_STAGE_DEACTIVATE && stage != PHP_INI_STAGE_SHUTDOWN) {
ZEND_HASH_FOREACH_STR_KEY(*p, funcname) {
if ((func = zend_hash_find_ptr(EG(function_table), funcname))) {
if ((func = zend_hash_find_ptr(EG(function_table), funcname)) && ZEND_OBSERVER_DATA(func) != NULL) {
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I don't understand this. ZEND_OBSERVER_DATA() expands to &RUN_TIME_CACHE(op_array)[handle], which cannot be NULL (except for RUN_TIME_CACHE(op_array) == NULL && handle == 0, which is undefined behavior). Removing these two conditions still makes the test pass. Should this have dereferenced the pointer?

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Actually, it probably must handle ZEND_OBSERVER_NOT_OBSERVED and ZEND_OBSERVER_NONE_OBSERVED. But I forgot about the details of this api.

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@bwoebi bwoebi Oct 22, 2024 •
edited
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@iluuu1994 The value is NULL if the observer has not been initialized yet. It's non-NULL once the init handler ran, assigning a specific handler or one of these two constants. Here we only care about initialized.
But it seems to be missing a dereference, yes. (In PHP 8.3 and before it evaluated to the first value. Hence I missed this.)

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I'll have a look as soon as possible.

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@iluuu1994, this PR targets PHP-8.4; the definition of ZEND_OBSERVER_DATA() has changed there:

php-src/Zend/zend_observer.h

Lines 39 to 40 in 5892991

#define ZEND_OBSERVER_DATA(function) \
((zend_observer_fcall_begin_handler *)&ZEND_OP_ARRAY_EXTENSION((&(function)->common), ZEND_OBSERVER_HANDLE(function)))

That part is needed if zend_test.observer.enabled=1 upfront (default for our Circle CI job).

@bwoebi, when running the test with zend_test.observer.enabled=1, ZEND_OBSERVER_DATA(func) is NULL for me.

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@iluuu1994 iluuu1994 Oct 22, 2024 •
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It's because RUN_TIME_CACHE(&func->common) is NULL, so doing pointer arithmetics on it is UB. In that case, I think we should check whether RUN_TIME_CACHE(&func->common) is set. Note that you're lucky here, if observer had a higher handle, this check would break.

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Ah, thank you! I'll have a closer look again, and might actually go with the hash table.

void *old_handler;
zend_observer_remove_begin_handler(func, observer_begin, (zend_observer_fcall_begin_handler *)&old_handler);
zend_observer_remove_end_handler(func, observer_end, (zend_observer_fcall_end_handler *)&old_handler);
Expand All @@ -329,7 +332,7 @@ static ZEND_INI_MH(zend_test_observer_OnUpdateCommaList)
zend_string_release(str);
if (stage != PHP_INI_STAGE_STARTUP && stage != PHP_INI_STAGE_ACTIVATE && stage != PHP_INI_STAGE_DEACTIVATE && stage != PHP_INI_STAGE_SHUTDOWN) {
ZEND_HASH_FOREACH_STR_KEY(*p, funcname) {
if ((func = zend_hash_find_ptr(EG(function_table), funcname))) {
if ((func = zend_hash_find_ptr(EG(function_table), funcname)) && ZEND_OBSERVER_DATA(func) != NULL) {
zend_observer_add_begin_handler(func, observer_begin);
zend_observer_add_end_handler(func, observer_end);
}
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13 changes: 13 additions & 0 deletions ext/zend_test/tests/gh16414.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
--TEST--
GH-16414 (zend_test.observer.observe_function_names may segfault)
--EXTENSIONS--
zend_test
--INI--
zend_test.observer.enabled=0
--FILE--
<?php
function bar() {}
var_dump(ini_set("zend_test.observer.observe_function_names", "bar"));
?>
--EXPECT--
bool(false)