Fix #74267: segfault with streams and invalid data

If the current character is a line break character, it cannot be a tab
or space character, so we would always fail with an invalid sequence
error.  Obviously, these `scan_stat == 4` conditions are meant to be
exclusive.

Furthermore, if `in_pp == NULL || in_left_p == NULL` is true, we hit a
segfault if we are not returning right away.  Obviously, the additional
constraints don't make sense, so we remove them.

(cherry picked from commit 12c59f6)
(cherry picked from commit d149a44)
(cherry picked from commit c173da7)

Author: cmb69

ext/standard/filters.c

@@ -790,7 +790,7 @@ static php_conv_err_t php_conv_qprint_encode_convert(php_conv_qprint_encode *ins
 	lb_ptr = inst->lb_ptr;
 	lb_cnt = inst->lb_cnt;
 
-	if ((in_pp == NULL || in_left_p == NULL) && (lb_ptr >=lb_cnt)) {
+	if (in_pp == NULL || in_left_p == NULL) {
 		return PHP_CONV_ERR_SUCCESS;
 	}
 
@@ -1018,7 +1018,7 @@ static php_conv_err_t php_conv_qprint_decode_convert(php_conv_qprint_decode *ins
 	lb_ptr = inst->lb_ptr;
 	lb_cnt = inst->lb_cnt;
 
-	if ((in_pp == NULL || in_left_p == NULL) && lb_cnt == lb_ptr) {
+	if (in_pp == NULL || in_left_p == NULL) {
 		if (inst->scan_stat != 0) {
 			return PHP_CONV_ERR_UNEXPECTED_EOS;
 		}
@@ -1115,8 +1115,7 @@ static php_conv_err_t php_conv_qprint_decode_convert(php_conv_qprint_decode *ins
 					*ps == (unsigned char)inst->lbchars[lb_cnt]) {
 					lb_cnt++;
 					scan_stat = 5;
-				}
-				if (*ps != '\t' && *ps != ' ') {
+				} else if (*ps != '\t' && *ps != ' ') {
 					err = PHP_CONV_ERR_INVALID_SEQ;
 					goto out;
 				}

ext/standard/tests/filters/bug74267.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Bug #74267 (segfault with streams and invalid data)
+--FILE--
+<?php
+$stream = fopen('php://memory', 'w');
+stream_filter_append($stream, 'convert.quoted-printable-decode', STREAM_FILTER_WRITE, ['line-break-chars' => "\r\n"]);
+
+$lines = [
+	"\r\n",
+	" -=()\r\n",
+	" -=\r\n",
+	"\r\n"
+	];
+
+foreach ($lines as $line) {
+	fwrite($stream, $line);
+}
+
+fclose($stream);
+echo "done\n";
+?>
+--EXPECTF--
+Warning: fwrite(): stream filter (convert.quoted-printable-decode): invalid byte sequence in %s on line %d
+
+Warning: fwrite(): stream filter (convert.quoted-printable-decode): invalid byte sequence in %s on line %d
+done