Security fix for CVE-2022-38171.
Extracted from upstream 4.04

Index: xpdf/JBIG2Stream.cc
--- xpdf/JBIG2Stream.cc.orig
+++ xpdf/JBIG2Stream.cc
@@ -1977,7 +1977,14 @@ void JBIG2Stream::readTextRegionSeg(Guint segNum, GBoo
   for (i = 0; i < nRefSegs; ++i) {
     if ((seg = findSegment(refSegs[i]))) {
       if (seg->getType() == jbig2SegSymbolDict) {
-	numSyms += ((JBIG2SymbolDict *)seg)->getSize();
+	Guint segSize = ((JBIG2SymbolDict *)seg)->getSize();
+	if (segSize > INT_MAX || numSyms > INT_MAX - segSize) {
+	  error(errSyntaxError, getPos(),
+		"Too many symbols in JBIG2 text region");
+	  delete codeTables;
+	  return;
+	}
+	numSyms += segSize;
       } else if (seg->getType() == jbig2SegCodeTable) {
 	codeTables->append(seg);
       }