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Zend: user opcode DISPATCH runs on a stale frame in the TAILCALL VM. #24109

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Zend: user opcode DISPATCH runs on a stale frame in the TAILCALL VM. #24109

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9512c51
Zend: user opcode DISPATCH runs on a stale frame in the TAILCALL VM.
devnexen Oct 3, 2026
5952ca9
add test
devnexen Oct 3, 2026
9481086
fix test attempt
devnexen Oct 4, 2026
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6 changes: 4 additions & 2 deletions Zend/zend_vm_execute.h
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6 changes: 4 additions & 2 deletions Zend/zend_vm_gen.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1917,7 +1917,7 @@ function gen_executor($f, $skl, $spec, $kind, $executor_name, $initializer_name)
out($f,"static const zend_op call_interrupt_op;\n");
out($f,"#endif\n\n");
}
out($f,"#if (ZEND_VM_KIND != ZEND_VM_KIND_HYBRID && ZEND_VM_KIND != ZEND_VM_KIND_TAILCALL) || !ZEND_VM_SPEC\n");
out($f,"#if ZEND_VM_KIND != ZEND_VM_KIND_HYBRID || !ZEND_VM_SPEC\n");
out($f,"static zend_vm_opcode_handler_t zend_vm_get_opcode_handler(uint8_t opcode, const zend_op* op);\n");
out($f,"#endif\n\n");
if ($kind == ZEND_VM_KIND_HYBRID) {
Expand Down Expand Up @@ -2146,6 +2146,7 @@ function gen_executor($f, $skl, $spec, $kind, $executor_name, $initializer_name)
out($f,"# undef ZEND_VM_INTERRUPT\n");
out($f,"# undef ZEND_VM_ENTER_EX\n");
out($f,"# undef ZEND_VM_LEAVE\n");
out($f,"# undef ZEND_VM_DISPATCH\n");
out($f,"\n");
out($f,"# define ZEND_VM_TAIL_CALL(call) ZEND_MUSTTAIL return call\n");
out($f,"# define ZEND_VM_CONTINUE() ZEND_VM_TAIL_CALL(opline->handler(ZEND_OPCODE_HANDLER_ARGS_PASSTHRU))\n");
Expand All @@ -2159,6 +2160,7 @@ function gen_executor($f, $skl, $spec, $kind, $executor_name, $initializer_name)
out($f,"# define ZEND_VM_INTERRUPT() ZEND_VM_TAIL_CALL(zend_interrupt_TAILCALL(ZEND_OPCODE_HANDLER_ARGS_PASSTHRU))\n");
out($f,"# define ZEND_VM_ENTER_EX() ZEND_VM_INTERRUPT_CHECK(); ZEND_VM_CONTINUE()\n");
out($f,"# define ZEND_VM_LEAVE() ZEND_VM_CONTINUE()\n");
out($f,"# define ZEND_VM_DISPATCH(opcode, opline) ZEND_VM_TAIL_CALL(zend_vm_get_opcode_handler(opcode, opline)(ZEND_OPCODE_HANDLER_ARGS_PASSTHRU))\n");
out($f,"\n");
out($f,"static ZEND_OPCODE_HANDLER_RET ZEND_OPCODE_HANDLER_CCONV zend_interrupt_helper".($spec?"_SPEC":"")."_TAILCALL(ZEND_OPCODE_HANDLER_ARGS);\n");
out($f,"static ZEND_OPCODE_HANDLER_RET ZEND_OPCODE_HANDLER_FUNC_CCONV zend_interrupt(ZEND_OPCODE_HANDLER_ARGS);\n");
Expand Down Expand Up @@ -3042,7 +3044,7 @@ function gen_vm($def, $skel) {
out($f, "\treturn (spec & SPEC_START_MASK) + offset;\n");
}
out($f, "}\n\n");
out($f, "#if (ZEND_VM_KIND != ZEND_VM_KIND_HYBRID && ZEND_VM_KIND != ZEND_VM_KIND_TAILCALL) || !ZEND_VM_SPEC\n");
out($f, "#if ZEND_VM_KIND != ZEND_VM_KIND_HYBRID || !ZEND_VM_SPEC\n");
out($f, "static zend_vm_opcode_handler_t zend_vm_get_opcode_handler(uint8_t opcode, const zend_op* op)\n");
out($f, "{\n");
if (!ZEND_VM_SPEC) {
Expand Down
24 changes: 24 additions & 0 deletions ext/zend_test/tests/gh24081.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
--TEST--
GH-24081 (User opcode handlers resume execution against a stale frame under ZEND_VM_KIND_TAILCALL)
--EXTENSIONS--
zend_test
--INI--
opcache.jit=disable
zend_test.observer.enabled=1
zend_test.observer.show_opcode_in_user_handler=ZEND_ADD
--FILE--
<?php
function f($a, $b) {
$r = $a + $b;
return strlen("x") + $r;
}

var_dump(f(1, 2));
?>
--EXPECTF--
<!-- init '%s' -->
<!-- init f() -->
<!-- opcode: 'ZEND_ADD' in user handler -->
<!-- opcode: 'ZEND_ADD' in user handler -->
<!-- init var_dump() -->
int(4)
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