From d8165c2502516dfda506e2f27aadec58041273ff Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv@gmail.com>
Date: Tue, 8 Jun 2021 14:31:55 +0200
Subject: [PATCH] Fixed bug #81104

When the memory limit is restored during shutdown, we may still
be using a lot of memory. Ignore the failure at that point and
set it again after the MM is shut down, at which point memory
usage should be at its lowest point.
---
 Zend/tests/bug81104.phpt | 23 +++++++++++++++++++++++
 main/main.c              | 14 ++++++++++++--
 2 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 Zend/tests/bug81104.phpt

diff --git a/Zend/tests/bug81104.phpt b/Zend/tests/bug81104.phpt
new file mode 100644
index 00000000000..fec7a7d25ef
--- /dev/null
+++ b/Zend/tests/bug81104.phpt
@@ -0,0 +1,23 @@
+--TEST--
+Bug #81104: Warning: "Failed to set memory limit to ... bytes" emitted after exit in debug
+--INI--
+memory_limit=5M
+report_memleaks=0
+--FILE--
+<?php
+class X {
+    public $x;
+    public function __construct() { $this->x = [$this]; }
+}
+gc_disable();
+ini_set('memory_limit', '10M');
+$y = [];
+for ($i = 0; $i < 10000; $i++) {
+    $y[] = new X();
+}
+$y[0]->y = &$y;
+
+?>
+===DONE===
+--EXPECT--
+===DONE===
diff --git a/main/main.c b/main/main.c
index e675998575f..503d46d1904 100644
--- a/main/main.c
+++ b/main/main.c
@@ -303,8 +303,14 @@ static PHP_INI_MH(OnChangeMemoryLimit)
 		value = Z_L(1)<<30;		/* effectively, no limit */
 	}
 	if (zend_set_memory_limit(value) == FAILURE) {
-		zend_error(E_WARNING, "Failed to set memory limit to %zd bytes (Current memory usage is %zd bytes)", value, zend_memory_usage(true));
-		return FAILURE;
+		/* When the memory limit is reset to the original level during deactivation, we may be
+		 * using more memory than the original limit while shutdown is still in progress.
+		 * Ignore a failure for now, and set the memory limit when the memory manager has been
+		 * shut down and the minimal amount of memory is used. */
+		if (stage != ZEND_INI_STAGE_DEACTIVATE) {
+			zend_error(E_WARNING, "Failed to set memory limit to %zd bytes (Current memory usage is %zd bytes)", value, zend_memory_usage(true));
+			return FAILURE;
+		}
 	}
 	PG(memory_limit) = value;
 	return SUCCESS;
@@ -1963,6 +1969,10 @@ void php_request_shutdown(void *dummy)
 		shutdown_memory_manager(CG(unclean_shutdown) || !report_memleaks, 0);
 	} zend_end_try();
 
+	/* Reset memory limit, as the reset during INI_STAGE_DEACTIVATE may have failed.
+	 * At this point, no memory beyond a single chunk should be in use. */
+	zend_set_memory_limit(PG(memory_limit));
+
 	/* 16. Deactivate Zend signals */
 #ifdef ZEND_SIGNALS
 	zend_signal_deactivate();