Fixed bug #78272

Use MAP_JIT only when running under hardened runtime, because MAP_JIT
is incompatible with fork().

The check is based on
f879e35e3e.

NEWS

@@ -14,6 +14,10 @@ PHP                                                                        NEWS
   . Fixed bug #78525 (Memory leak in pdo when reusing native prepared
     statements). (Nikita)
 
+- PCRE:
+  . Fixed bug #78272 (calling preg_match() before pcntl_fork() will freeze
+    child process). (Nikita)
+
 - Standard:
   . Fixed bug #76342 (file_get_contents waits twice specified timeout).
     (Thomas Calvet)

ext/pcre/pcre2lib/sljit/sljitExecAllocator.c

@@ -121,7 +121,20 @@ static SLJIT_INLINE int get_map_jit_flag()
 		uname(&name);
 
 		/* Kernel version for 10.14.0 (Mojave) */
-		map_jit_flag = (atoi(name.release) >= 18) ? MAP_JIT : 0;
+		if (atoi(name.release) >= 18) {
+			/* Only use MAP_JIT if a hardened runtime is used, because MAP_JIT is incompatible
+			   with fork(). */
+			void *ptr = mmap(
+				NULL, getpagesize(), PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+			if (ptr == MAP_FAILED) {
+				map_jit_flag = MAP_JIT;
+			} else {
+				map_jit_flag = 0;
+				munmap(ptr, getpagesize());
+			}
+		} else {
+			map_jit_flag = 0;
+		}
 	}
 
 	return map_jit_flag;

ext/pcre/tests/bug78272.phpt

@@ -0,0 +1,33 @@
+--TEST--
+Bug #78272: calling preg_match() before pcntl_fork() will freeze child process
+--SKIPIF--
+<?php
+if (!extension_loaded('pcntl')) die("skip pcntl extension required");
+?>
+--FILE--
+<?php
+preg_match('/abc/', 'abcde', $r);
+
+$pid = pcntl_fork();
+if ($pid === 0) {
+    print "Child start\n";
+    preg_match('/abc/', 'abcde', $r);
+    print_r($r);
+    print "End child\n";
+    exit(0);
+} else {
+    print "Main start\n";
+    pcntl_waitpid($pid, $status);
+    print "End Main\n";
+    exit(0);
+}
+?>
+--EXPECT--
+Main start
+Child start
+Array
+(
+    [0] => abc
+)
+End child
+End Main