static int vorbis_decode_packet_rest(vorb *f, int *len, Mode *m, int left_start, int left_end, int right_start, int right_end, int *p_left)
{
   Mapping *map;
   int i,j,k,n,n2;
   int zero_channel[256];
   int really_zero_channel[256];


   n = f->blocksize[m->blockflag];
   map = &f->mapping[m->mapping];

   n2 = n >> 1;

   CHECK(f);

   for (i=0; i < f->channels; ++i) {
      int s = map->chan[i].mux, floor;
      zero_channel[i] = FALSE;
      floor = map->submap_floor[s];
      if (f->floor_types[floor] == 0) {
         return error(f, VORBIS_invalid_stream);
      } else {
         Floor1 *g = &f->floor_config[floor].floor1;
         if (get_bits(f, 1)) {
            short *finalY;
            uint8 step2_flag[256];
            static int range_list[4] = { 256, 128, 86, 64 };
            int range = range_list[g->floor1_multiplier-1];
            int offset = 2;
            finalY = f->finalY[i];
            finalY[0] = get_bits(f, ilog(range)-1);
            finalY[1] = get_bits(f, ilog(range)-1);
            for (j=0; j < g->partitions; ++j) {
               int pclass = g->partition_class_list[j];
               int cdim = g->class_dimensions[pclass];
               int cbits = g->class_subclasses[pclass];
               int csub = (1 << cbits)-1;
               int cval = 0;
               if (cbits) {
                  Codebook *c = f->codebooks + g->class_masterbooks[pclass];
                  DECODE(cval,f,c);
               }
               for (k=0; k < cdim; ++k) {
                  int book = g->subclass_books[pclass][cval & csub];
                  cval = cval >> cbits;
                  if (book >= 0) {
                     int temp;
                     Codebook *c = f->codebooks + book;
                     DECODE(temp,f,c);
                     finalY[offset++] = temp;
                  } else
                     finalY[offset++] = 0;
               }
            }
            if (f->valid_bits == INVALID_BITS) goto error; // behavior according to spec
            step2_flag[0] = step2_flag[1] = 1;
            for (j=2; j < g->values; ++j) {
               int low, high, pred, highroom, lowroom, room, val;
               low = g->neighbors[j][0];
               high = g->neighbors[j][1];
               pred = predict_point(g->Xlist[j], g->Xlist[low], g->Xlist[high], finalY[low], finalY[high]);
               val = finalY[j];
               highroom = range - pred;
               lowroom = pred;
               if (highroom < lowroom)
                  room = highroom * 2;
               else
                  room = lowroom * 2;
               if (val) {
                  step2_flag[low] = step2_flag[high] = 1;
                  step2_flag[j] = 1;
                  if (val >= room)
                     if (highroom > lowroom)
                        finalY[j] = val - lowroom + pred;
                     else
                        finalY[j] = pred - val + highroom - 1;
                  else
                     if (val & 1)
                        finalY[j] = pred - ((val+1)>>1);
                     else
                        finalY[j] = pred + (val>>1);
               } else {
                  step2_flag[j] = 0;
                  finalY[j] = pred;
               }
            }

#ifdef STB_VORBIS_NO_DEFER_FLOOR
            do_floor(f, map, i, n, f->floor_buffers[i], finalY, step2_flag);
#else
            for (j=0; j < g->values; ++j) {
               if (!step2_flag[j])
                  finalY[j] = -1;
            }
#endif
         } else {
           error:
            zero_channel[i] = TRUE;
         }

      }
   }
   CHECK(f);

   if (f->alloc.alloc_buffer)
      assert(f->alloc.alloc_buffer_length_in_bytes == f->temp_offset);

   memcpy(really_zero_channel, zero_channel, sizeof(really_zero_channel[0]) * f->channels);
   for (i=0; i < map->coupling_steps; ++i)
      if (!zero_channel[map->chan[i].magnitude] || !zero_channel[map->chan[i].angle]) {
         zero_channel[map->chan[i].magnitude] = zero_channel[map->chan[i].angle] = FALSE;
      }

   CHECK(f);
   for (i=0; i < map->submaps; ++i) {
      float *residue_buffers[STB_VORBIS_MAX_CHANNELS];
      int r;
      uint8 do_not_decode[256];
      int ch = 0;
      for (j=0; j < f->channels; ++j) {
         if (map->chan[j].mux == i) {
            if (zero_channel[j]) {
               do_not_decode[ch] = TRUE;
               residue_buffers[ch] = NULL;
            } else {
               do_not_decode[ch] = FALSE;
               residue_buffers[ch] = f->channel_buffers[j];
            }
            ++ch;
         }
      }
      r = map->submap_residue[i];
      decode_residue(f, residue_buffers, ch, n2, r, do_not_decode);
   }

   if (f->alloc.alloc_buffer)
      assert(f->alloc.alloc_buffer_length_in_bytes == f->temp_offset);
   CHECK(f);

   for (i = map->coupling_steps-1; i >= 0; --i) {
      int n2 = n >> 1;
      float *m = f->channel_buffers[map->chan[i].magnitude];
      float *a = f->channel_buffers[map->chan[i].angle    ];
      for (j=0; j < n2; ++j) {
         float a2,m2;
         if (m[j] > 0)
            if (a[j] > 0)
               m2 = m[j], a2 = m[j] - a[j];
            else
               a2 = m[j], m2 = m[j] + a[j];
         else
            if (a[j] > 0)
               m2 = m[j], a2 = m[j] + a[j];
            else
               a2 = m[j], m2 = m[j] - a[j];
         m[j] = m2;
         a[j] = a2;
      }
   }
   CHECK(f);

#ifndef STB_VORBIS_NO_DEFER_FLOOR
   for (i=0; i < f->channels; ++i) {
      if (really_zero_channel[i]) {
         memset(f->channel_buffers[i], 0, sizeof(*f->channel_buffers[i]) * n2);
      } else {
         do_floor(f, map, i, n, f->channel_buffers[i], f->finalY[i], NULL);
      }
   }
#else
   for (i=0; i < f->channels; ++i) {
      if (really_zero_channel[i]) {
         memset(f->channel_buffers[i], 0, sizeof(*f->channel_buffers[i]) * n2);
      } else {
         for (j=0; j < n2; ++j)
            f->channel_buffers[i][j] *= f->floor_buffers[i][j];
      }
   }
#endif

   CHECK(f);
   for (i=0; i < f->channels; ++i)
      inverse_mdct(f->channel_buffers[i], n, f, m->blockflag);
   CHECK(f);

   flush_packet(f);

   if (f->first_decode) {
      f->current_loc = -n2; // start of first frame is positioned for discard
      f->discard_samples_deferred = n - right_end;
      f->current_loc_valid = TRUE;
      f->first_decode = FALSE;
   } else if (f->discard_samples_deferred) {
      if (f->discard_samples_deferred >= right_start - left_start) {
         f->discard_samples_deferred -= (right_start - left_start);
         left_start = right_start;
         *p_left = left_start;
      } else {
         left_start += f->discard_samples_deferred;
         *p_left = left_start;
         f->discard_samples_deferred = 0;
      }
   } else if (f->previous_length == 0 && f->current_loc_valid) {
   }

   if (f->last_seg_which == f->end_seg_with_known_loc) {
      if (f->current_loc_valid && (f->page_flag & PAGEFLAG_last_page)) {
         uint32 current_end = f->known_loc_for_packet;
         if (current_end < f->current_loc + (right_end-left_start)) {
            if (current_end < f->current_loc) {
               *len = 0;
            } else {
               *len = current_end - f->current_loc;
            }
            *len += left_start; // this doesn't seem right, but has no ill effect on my test files
            if (*len > right_end) *len = right_end; // this should never happen
            f->current_loc += *len;
            return TRUE;
         }
      }
      f->current_loc = f->known_loc_for_packet - (n2-left_start);
      f->current_loc_valid = TRUE;
   }
   if (f->current_loc_valid)
      f->current_loc += (right_start - left_start);

   if (f->alloc.alloc_buffer)
      assert(f->alloc.alloc_buffer_length_in_bytes == f->temp_offset);
   *len = right_end;  // ignore samples after the window goes to 0
   CHECK(f);

   return TRUE;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.