Fix GH-16409: Segfault in exif_thumbnail when not dealing with a real file

Closes GH-16416.

NEWS

@@ -17,6 +17,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-16316 (DOMXPath breaks when not initialized properly).
     (nielsdos)
 
+- EXIF:
+  . Fixed bug GH-16409 (Segfault in exif_thumbnail when not dealing with a
+    real file). (nielsdos, cmb)
+
 - GD:
   . Fixed bug GH-16334 (imageaffine overflow on matrix elements).
     (David Carlier)

ext/exif/exif.c

@@ -4419,7 +4419,7 @@ static bool exif_read_from_impl(image_info_type *ImageInfo, php_stream *stream,
 	ImageInfo->FileName			= NULL;
 
 	if (php_stream_is(ImageInfo->infile, PHP_STREAM_IS_STDIO)) {
-		if (VCWD_STAT(stream->orig_path, &st) >= 0) {
+		if (stream->orig_path && VCWD_STAT(stream->orig_path, &st) >= 0) {
 			zend_string *base;
 			if ((st.st_mode & S_IFMT) != S_IFREG) {
 				exif_error_docref(NULL EXIFERR_CC, ImageInfo, E_WARNING, "Not a file");

ext/exif/tests/gh16409.phpt

@@ -0,0 +1,12 @@
+--TEST--
+GH-16409 (Segfault in exif_thumbnail when not dealing with a real file)
+--EXTENSIONS--
+exif
+--FILE--
+<?php
+$stream = popen('echo 1', 'r');
+var_dump(exif_thumbnail($stream, $pipes, $stream, $pipes));
+?>
+--EXPECTF--
+Warning: exif_thumbnail(): File too small (0) in %s on line %d
+bool(false)%A