Skip to content

Fix GH-17442: Engine UAF with reference assign and dtor #17443

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 3 commits into from
Closed

Fix GH-17442: Engine UAF with reference assign and dtor #17443

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
65ae09b
Fix GH-17442: Engine UAF with reference assign and dtor
nielsdos Jan 11, 2025
a8b5271
Address review comment
nielsdos Jan 27, 2025
d93aa1b
Use GC_DTOR_NO_REF
nielsdos Jan 28, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions UPGRADING.INTERNALS
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,11 @@ PHP 8.5 INTERNALS UPGRADE NOTES
1. Internal API changes
========================

- Zend
. Added ZEND_SAFE_ASSIGN_VALUE() macro to safely assign a value to a zval.
. Added zval_ptr_safe_dtor() to safely destroy a zval when a destructor
could interfere.

========================
2. Build system changes
========================
Expand Down
22 changes: 22 additions & 0 deletions Zend/tests/weakrefs/gh17442_1.phpt
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
--TEST--
GH-17442 (Engine UAF with reference assign and dtor) - untyped
--CREDITS--
YuanchengJiang
--FILE--
<?php
$map = new WeakMap;
$obj = new stdClass;
$map[$obj] = new class {
function __destruct() {
throw new Exception("Test");
}
};
headers_sent($obj,$generator);
?>
--EXPECTF--
Fatal error: Uncaught Exception: Test in %s:%d
Stack trace:
#0 [internal function]: class@anonymous->__destruct()
#1 %s(%d): headers_sent(NULL, 0)
#2 {main}
thrown in %s on line %d
35 changes: 35 additions & 0 deletions Zend/tests/weakrefs/gh17442_2.phpt
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
--TEST--
GH-17442 (Engine UAF with reference assign and dtor) - typed
--CREDITS--
YuanchengJiang
nielsdos
--FILE--
<?php
$map = new WeakMap;

class Test {
public stdClass|string $obj;
}

$test = new Test;
$test->obj = new stdClass;

$map[$test->obj] = new class {
function __destruct() {
global $test;
var_dump($test->obj);
throw new Exception("Test");
}
};

headers_sent($test->obj);
?>
--EXPECTF--
string(0) ""

Fatal error: Uncaught Exception: Test in %s:%d
Stack trace:
#0 [internal function]: class@anonymous->__destruct()
#1 %s(%d): headers_sent('')
#2 {main}
thrown in %s on line %d
3 changes: 1 addition & 2 deletions Zend/zend_API.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4666,8 +4666,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_ex(zend_reference *ref, zval *val
zval_ptr_dtor(val);
return FAILURE;
} else {
zval_ptr_dtor(&ref->val);
ZVAL_COPY_VALUE(&ref->val, val);
ZEND_SAFE_ASSIGN_VALUE(&ref->val, val);
return SUCCESS;
}
}
Expand Down
53 changes: 33 additions & 20 deletions Zend/zend_API.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1097,6 +1097,22 @@ ZEND_API zend_result zend_try_assign_typed_ref_res(zend_reference *ref, zend_res
ZEND_API zend_result zend_try_assign_typed_ref_zval(zend_reference *ref, zval *zv);
ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval *zv, bool strict);

#define ZEND_SAFE_ASSIGN_VALUE(zv, value) do { \
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

We already have very similar zend_assign_to_variable() in zend_execute.h.
This one does almost the same except for reference support.
I think this sholud be named somehow more consistently and may be moved to zend_execute.h

The rest looks fine.

zval *_zv = zv; \
zval *_value = value; \
if (Z_REFCOUNTED_P(_zv)) { \
zend_refcounted *rc = Z_COUNTED_P(_zv); \
ZVAL_COPY_VALUE(_zv, _value); \
if (!GC_DELREF(rc)) { \
rc_dtor_func(rc); \
} else { \
gc_check_possible_root(rc); \
} \
} else { \
ZVAL_COPY_VALUE(_zv, _value); \
} \
} while (0)

#define _ZEND_TRY_ASSIGN_NULL(zv, is_ref) do { \
zval *_zv = zv; \
if (is_ref || UNEXPECTED(Z_ISREF_P(_zv))) { \
Expand All @@ -1107,7 +1123,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_NULL(_zv); \
} while (0)

Expand All @@ -1129,7 +1145,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_FALSE(_zv); \
} while (0)

Expand All @@ -1151,7 +1167,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_TRUE(_zv); \
} while (0)

Expand All @@ -1173,7 +1189,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_BOOL(_zv, bval); \
} while (0)

Expand All @@ -1195,7 +1211,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_LONG(_zv, lval); \
} while (0)

Expand All @@ -1217,7 +1233,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_DOUBLE(_zv, dval); \
} while (0)

Expand All @@ -1239,7 +1255,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_EMPTY_STRING(_zv); \
} while (0)

Expand All @@ -1261,7 +1277,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_STR(_zv, str); \
} while (0)

Expand All @@ -1283,7 +1299,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_NEW_STR(_zv, str); \
} while (0)

Expand All @@ -1305,7 +1321,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_STRING(_zv, string); \
} while (0)

Expand All @@ -1327,7 +1343,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_STRINGL(_zv, string, len); \
} while (0)

Expand All @@ -1349,7 +1365,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_ARR(_zv, arr); \
} while (0)

Expand All @@ -1371,7 +1387,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_RES(_zv, res); \
} while (0)

Expand All @@ -1393,7 +1409,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_COPY_VALUE(_zv, other_zv); \
} while (0)

Expand All @@ -1415,7 +1431,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_COPY_VALUE(_zv, other_zv); \
} while (0)

Expand Down Expand Up @@ -1447,7 +1463,7 @@ ZEND_API zend_result zend_try_assign_typed_ref_zval_ex(zend_reference *ref, zval
} \
_zv = &ref->val; \
} \
zval_ptr_dtor(_zv); \
zval_ptr_safe_dtor(_zv); \
ZVAL_COPY_VALUE(_zv, other_zv); \
} while (0)

Expand Down Expand Up @@ -1485,10 +1501,7 @@ static zend_always_inline zval *zend_try_array_init_size(zval *zv, uint32_t size
}
zv = &ref->val;
}
zval garbage;
ZVAL_COPY_VALUE(&garbage, zv);
ZVAL_NULL(zv);
zval_ptr_dtor(&garbage);
zval_ptr_safe_dtor(zv);
ZVAL_ARR(zv, arr);
return zv;
}
Expand Down
14 changes: 14 additions & 0 deletions Zend/zend_variables.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,20 @@ ZEND_API void zval_ptr_dtor(zval *zval_ptr) /* {{{ */
}
/* }}} */

ZEND_API void zval_ptr_safe_dtor(zval *zval_ptr)
{
if (Z_REFCOUNTED_P(zval_ptr)) {
zend_refcounted *ref = Z_COUNTED_P(zval_ptr);

if (GC_DELREF(ref) == 0) {
ZVAL_NULL(zval_ptr);
rc_dtor_func(ref);
} else {
gc_check_possible_root(ref);
}
}
}

ZEND_API void zval_internal_ptr_dtor(zval *zval_ptr) /* {{{ */
{
if (Z_REFCOUNTED_P(zval_ptr)) {
Expand Down
1 change: 1 addition & 0 deletions Zend/zend_variables.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,7 @@ static zend_always_inline void zval_ptr_dtor_str(zval *zval_ptr)
}

ZEND_API void zval_ptr_dtor(zval *zval_ptr);
ZEND_API void zval_ptr_safe_dtor(zval *zval_ptr);
ZEND_API void zval_internal_ptr_dtor(zval *zvalue);

/* Kept for compatibility */
Expand Down
Loading