JPEG-LS: clip offset based on cur_scan to valid range.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>

libavcodec/jpeglsdec.c

@@ -286,8 +286,8 @@ int ff_jpegls_decode_picture(MJpegDecodeContext *s, int near, int point_transfor
 //    av_log(s->avctx, AV_LOG_DEBUG, "JPEG-LS params: %ix%i NEAR=%i MV=%i T(%i,%i,%i) RESET=%i, LIMIT=%i, qbpp=%i, RANGE=%i\n",s->width,s->height,state->near,state->maxval,state->T1,state->T2,state->T3,state->reset,state->limit,state->qbpp, state->range);
 //    av_log(s->avctx, AV_LOG_DEBUG, "JPEG params: ILV=%i Pt=%i BPP=%i, scan = %i\n", ilv, point_transform, s->bits, s->cur_scan);
     if(ilv == 0) { /* separate planes */
-        off = s->cur_scan - 1;
         stride = (s->nb_components > 1) ? 3 : 1;
+        off = av_clip(s->cur_scan - 1, 0, stride);
         width = s->width * stride;
         cur += off;
         for(i = 0; i < s->height; i++) {