Fixed bug #81298

Creation of the filter may fail for some special encodings, for
which detection is not supported.

Author: nikic

NEWS

@@ -2,6 +2,10 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.1.0beta2
 
+- Mbstring:
+  . Fixed bug #81298 (mb_detect_encoding() segfaults when 7bit encoding is
+    specified). (Nikita)
+
 - MySQLnd:
   . Fixed bug #63327 (Crash (Bus Error) in mysqlnd due to wrong alignment).
     (Nikita)

ext/mbstring/libmbfl/mbfl/mbfilter.c

@@ -315,12 +315,17 @@ mbfl_encoding_detector *mbfl_encoding_detector_new(const mbfl_encoding **elist,
 
 	mbfl_encoding_detector *identd = emalloc(sizeof(mbfl_encoding_detector));
 	identd->filter_list = ecalloc(elistsz, sizeof(mbfl_convert_filter*));
+
+	int filter_list_size = 0;
 	for (int i = 0; i < elistsz; i++) {
-		identd->filter_list[i] = mbfl_convert_filter_new(elist[i], &mbfl_encoding_wchar,
+		mbfl_convert_filter *filter = mbfl_convert_filter_new(elist[i], &mbfl_encoding_wchar,
 			mbfl_estimate_encoding_likelihood, NULL, &identd->filter_list[i]);
-		identd->filter_list[i]->opaque = (void*)0;
+		if (filter) {
+			identd->filter_list[filter_list_size++] = filter;
+			filter->opaque = (void*)0;
+		}
 	}
-	identd->filter_list_size = elistsz;
+	identd->filter_list_size = filter_list_size;
 	identd->strict = strict;
 	return identd;
 }

ext/mbstring/tests/bug81298.phpt

@@ -0,0 +1,12 @@
+--TEST--
+Bug #81298: mb_detect_encoding() segfaults when 7bit encoding is specified
+--FILE--
+<?php
+
+var_dump(mb_detect_encoding("foobar", "7bit"));
+var_dump(mb_detect_encoding("foobar", "7bit,ascii"));
+
+?>
+--EXPECT--
+bool(false)
+string(5) "ASCII"