avcodec/jpeg2000dec: move bpno check to a earlier place

This prevents additional integer overflows
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/jpeg2000dec.c

@@ -633,10 +633,16 @@ static int jpeg2000_decode_packet(Jpeg2000DecoderContext *s,
             else if (incl < 0)
                 return incl;
 
-            if (!cblk->npasses)
-                cblk->nonzerobits = expn[bandno] + numgbits - 1 -
+            if (!cblk->npasses) {
+                int v = expn[bandno] + numgbits - 1 -
                                     tag_tree_decode(s, prec->zerobits + cblkno,
                                                     100);
+                if (v < 0) {
+                    av_log(s->avctx, AV_LOG_ERROR, "nonzerobits %d invalid\n", v);
+                    return AVERROR_INVALIDDATA;
+                }
+                cblk->nonzerobits = v;
+            }
             if ((newpasses = getnpasses(s)) < 0)
                 return newpasses;
             if ((llen = getlblockinc(s)) < 0)
@@ -913,10 +919,6 @@ static int decode_cblk(Jpeg2000DecoderContext *s, Jpeg2000CodingStyle *codsty,
     ff_mqc_initdec(&t1->mqc, cblk->data);
 
     while (passno--) {
-        if (bpno < 0) {
-            av_log(s->avctx, AV_LOG_ERROR, "bpno invalid\n");
-            return AVERROR(EINVAL);
-        }
         switch(pass_t) {
         case 0:
             decode_sigpass(t1, width, height, bpno + 1, bandpos,