From 2bc6025c2cb2d17879fef55f91236088c6cb34e5 Mon Sep 17 00:00:00 2001
From: Aaron Piotrowski <aaron@trowski.com>
Date: Sat, 16 Jul 2022 13:05:16 -0500
Subject: [PATCH] Prevent fiber switching in tick function and signal handlers
 (#9028)

---
 Zend/tests/fibers/signal-async.phpt    | 37 +++++++++++++++++++++
 Zend/tests/fibers/signal-dispatch.phpt | 46 ++++++++++++++++++++++++++
 Zend/tests/fibers/ticks.phpt           | 33 ++++++++++++++++++
 Zend/zend_vm_def.h                     |  2 ++
 Zend/zend_vm_execute.h                 |  2 ++
 ext/pcntl/pcntl.c                      |  7 ++++
 6 files changed, 127 insertions(+)
 create mode 100644 Zend/tests/fibers/signal-async.phpt
 create mode 100644 Zend/tests/fibers/signal-dispatch.phpt
 create mode 100644 Zend/tests/fibers/ticks.phpt

diff --git a/Zend/tests/fibers/signal-async.phpt b/Zend/tests/fibers/signal-async.phpt
new file mode 100644
index 00000000000..f1f5a2f4c8f
--- /dev/null
+++ b/Zend/tests/fibers/signal-async.phpt
@@ -0,0 +1,37 @@
+--TEST--
+Prevent switching fibers when async signals are enabled
+--EXTENSIONS--
+pcntl
+posix
+--FILE--
+<?php
+
+pcntl_async_signals(true);
+
+pcntl_signal(SIGUSR1, function (): void {
+    if (Fiber::getCurrent() !== null) {
+        Fiber::suspend();
+    }
+});
+
+$fiber = new Fiber(function (): void {
+    echo "Fiber start\n";
+    posix_kill(posix_getpid(), SIGUSR1);
+    time_nanosleep(1);
+    echo "Fiber end\n";
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+Fiber start
+
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %ssignal-async.php:%d
+Stack trace:
+#0 %ssignal-async.php(%d): Fiber::suspend()
+#1 %ssignal-async.php(%d): {closure}(%d, Array)
+#2 [internal function]: {closure}()
+#3 %ssignal-async.php(%d): Fiber->start()
+#4 {main}
+  thrown in %ssignal-async.php on line %d
diff --git a/Zend/tests/fibers/signal-dispatch.phpt b/Zend/tests/fibers/signal-dispatch.phpt
new file mode 100644
index 00000000000..abde8e313d7
--- /dev/null
+++ b/Zend/tests/fibers/signal-dispatch.phpt
@@ -0,0 +1,46 @@
+--TEST--
+Prevent switching fibers when dispatching pending signals
+--EXTENSIONS--
+pcntl
+posix
+--FILE--
+<?php
+
+pcntl_signal(SIGUSR1, function (): void {
+    if (Fiber::getCurrent() !== null) {
+        Fiber::suspend();
+    }
+});
+
+$fiber = new Fiber(function (): void {
+    echo "Fiber start\n";
+
+    posix_kill(posix_getpid(), SIGUSR1);
+
+    try {
+        pcntl_signal_dispatch();
+    } catch (FiberError $e) {
+        Fiber::suspend($e);
+    }
+
+    echo "Fiber end\n";
+});
+
+$e = $fiber->start();
+
+echo $e, "\n";
+
+$fiber->resume();
+
+?>
+--EXPECTF--
+Fiber start
+FiberError: Cannot switch fibers in current execution context in %ssignal-dispatch.php:%d
+Stack trace:
+#0 %ssignal-dispatch.php(%d): Fiber::suspend()
+#1 [internal function]: {closure}(%d, Array)
+#2 %ssignal-dispatch.php(%d): pcntl_signal_dispatch()
+#3 [internal function]: {closure}()
+#4 %ssignal-dispatch.php(%d): Fiber->start()
+#5 {main}
+Fiber end
diff --git a/Zend/tests/fibers/ticks.phpt b/Zend/tests/fibers/ticks.phpt
new file mode 100644
index 00000000000..fbd050c09b9
--- /dev/null
+++ b/Zend/tests/fibers/ticks.phpt
@@ -0,0 +1,33 @@
+--TEST--
+Prevent switching fibers in tick function
+--FILE--
+<?php
+
+declare(ticks=1);
+
+register_tick_function(function (): void {
+    if (Fiber::getCurrent() !== null) {
+        Fiber::suspend();
+    }
+});
+
+$fiber = new Fiber(function (): void {
+    echo "1\n";
+    echo "2\n";
+    echo "3\n";
+});
+
+$fiber->start();
+
+?>
+--EXPECTF--
+1
+
+Fatal error: Uncaught FiberError: Cannot switch fibers in current execution context in %sticks.php:%d
+Stack trace:
+#0 %sticks.php(%d): Fiber::suspend()
+#1 %sticks.php(%d): {closure}()
+#2 [internal function]: {closure}()
+#3 %sticks.php(%d): Fiber->start()
+#4 {main}
+  thrown in %sticks.php on line %d
diff --git a/Zend/zend_vm_def.h b/Zend/zend_vm_def.h
index 9043cde725b..86557b6e2bf 100644
--- a/Zend/zend_vm_def.h
+++ b/Zend/zend_vm_def.h
@@ -7752,7 +7752,9 @@ ZEND_VM_HANDLER(105, ZEND_TICKS, ANY, ANY, NUM)
 		EG(ticks_count) = 0;
 		if (zend_ticks_function) {
 			SAVE_OPLINE();
+			zend_fiber_switch_block();
 			zend_ticks_function(opline->extended_value);
+			zend_fiber_switch_unblock();
 			ZEND_VM_NEXT_OPCODE_CHECK_EXCEPTION();
 		}
 	}
diff --git a/Zend/zend_vm_execute.h b/Zend/zend_vm_execute.h
index 39005c91849..13ba7443360 100644
--- a/Zend/zend_vm_execute.h
+++ b/Zend/zend_vm_execute.h
@@ -2996,7 +2996,9 @@ static ZEND_OPCODE_HANDLER_RET ZEND_FASTCALL ZEND_TICKS_SPEC_HANDLER(ZEND_OPCODE
 		EG(ticks_count) = 0;
 		if (zend_ticks_function) {
 			SAVE_OPLINE();
+			zend_fiber_switch_block();
 			zend_ticks_function(opline->extended_value);
+			zend_fiber_switch_unblock();
 			ZEND_VM_NEXT_OPCODE_CHECK_EXCEPTION();
 		}
 	}
diff --git a/ext/pcntl/pcntl.c b/ext/pcntl/pcntl.c
index fe4fe104a36..e1aedb101c9 100644
--- a/ext/pcntl/pcntl.c
+++ b/ext/pcntl/pcntl.c
@@ -34,6 +34,7 @@
 #include "pcntl_arginfo.h"
 #include "php_signal.h"
 #include "php_ticks.h"
+#include "zend_fibers.h"
 
 #if defined(HAVE_GETPRIORITY) || defined(HAVE_SETPRIORITY) || defined(HAVE_WAIT3)
 #include <sys/wait.h>
@@ -1410,6 +1411,9 @@ void pcntl_signal_dispatch()
 		return;
 	}
 
+	/* Prevent switching fibers when handling signals */
+	zend_fiber_switch_block();
+
 	/* Prevent reentrant handler calls */
 	PCNTL_G(processing_signal_queue) = 1;
 
@@ -1450,6 +1454,9 @@ void pcntl_signal_dispatch()
 	/* Re-enable queue */
 	PCNTL_G(processing_signal_queue) = 0;
 
+	/* Re-enable fiber switching */
+	zend_fiber_switch_unblock();
+
 	/* return signal mask to previous state */
 	sigprocmask(SIG_SETMASK, &old_mask, NULL);
 }