flxdec: Don't unref() parent in the chain function

We don't own the reference here, it is owned by the caller and given to
us for the scope of this function. Leftover mistake from 0.10 porting.

https://bugzilla.gnome.org/show_bug.cgi?id=774897

gst_flxdec_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
{
  GstCaps *caps;
  guint avail;
  GstFlowReturn res = GST_FLOW_OK;

  GstFlxDec *flxdec;
  FlxHeader *flxh;

  g_return_val_if_fail (buf != NULL, GST_FLOW_ERROR);
  flxdec = (GstFlxDec *) parent;
  g_return_val_if_fail (flxdec != NULL, GST_FLOW_ERROR);

  gst_adapter_push (flxdec->adapter, buf);
  avail = gst_adapter_available (flxdec->adapter);

  if (flxdec->state == GST_FLXDEC_READ_HEADER) {
    if (avail >= FlxHeaderSize) {
      const guint8 *data = gst_adapter_map (flxdec->adapter, FlxHeaderSize);
      GstCaps *templ;

      memcpy ((gchar *) & flxdec->hdr, data, FlxHeaderSize);
      FLX_HDR_FIX_ENDIANNESS (&(flxdec->hdr));
      gst_adapter_unmap (flxdec->adapter);
      gst_adapter_flush (flxdec->adapter, FlxHeaderSize);

      flxh = &flxdec->hdr;

      /* check header */
      if (flxh->type != FLX_MAGICHDR_FLI &&
          flxh->type != FLX_MAGICHDR_FLC && flxh->type != FLX_MAGICHDR_FLX)
        goto wrong_type;

      GST_LOG ("size      :  %d", flxh->size);
      GST_LOG ("frames    :  %d", flxh->frames);
      GST_LOG ("width     :  %d", flxh->width);
      GST_LOG ("height    :  %d", flxh->height);
      GST_LOG ("depth     :  %d", flxh->depth);
      GST_LOG ("speed     :  %d", flxh->speed);

      flxdec->next_time = 0;

      if (flxh->type == FLX_MAGICHDR_FLI) {
        flxdec->frame_time = JIFFIE * flxh->speed;
      } else if (flxh->speed == 0) {
        flxdec->frame_time = GST_SECOND / 70;
      } else {
        flxdec->frame_time = flxh->speed * GST_MSECOND;
      }

      flxdec->duration = flxh->frames * flxdec->frame_time;
      GST_LOG ("duration   :  %" GST_TIME_FORMAT,
          GST_TIME_ARGS (flxdec->duration));

      templ = gst_pad_get_pad_template_caps (flxdec->srcpad);
      caps = gst_caps_copy (templ);
      gst_caps_unref (templ);
      gst_caps_set_simple (caps,
          "width", G_TYPE_INT, flxh->width,
          "height", G_TYPE_INT, flxh->height,
          "framerate", GST_TYPE_FRACTION, (gint) GST_MSECOND,
          (gint) flxdec->frame_time / 1000, NULL);

      gst_pad_set_caps (flxdec->srcpad, caps);
      gst_caps_unref (caps);

      if (flxh->depth <= 8)
        flxdec->converter =
            flx_colorspace_converter_new (flxh->width, flxh->height);

      if (flxh->type == FLX_MAGICHDR_FLC || flxh->type == FLX_MAGICHDR_FLX) {
        GST_LOG ("(FLC) aspect_dx :  %d", flxh->aspect_dx);
        GST_LOG ("(FLC) aspect_dy :  %d", flxh->aspect_dy);
        GST_LOG ("(FLC) oframe1   :  0x%08x", flxh->oframe1);
        GST_LOG ("(FLC) oframe2   :  0x%08x", flxh->oframe2);
      }

      flxdec->size = ((guint) flxh->width * (guint) flxh->height);

      /* create delta and output frame */
      flxdec->frame_data = g_malloc (flxdec->size);
      flxdec->delta_data = g_malloc (flxdec->size);

      flxdec->state = GST_FLXDEC_PLAYING;
    }
  } else if (flxdec->state == GST_FLXDEC_PLAYING) {
    GstBuffer *out;

    /* while we have enough data in the adapter */
    while (avail >= FlxFrameChunkSize && res == GST_FLOW_OK) {
      FlxFrameChunk flxfh;
      guchar *chunk;
      const guint8 *data;
      GstMapInfo map;

      chunk = NULL;
      data = gst_adapter_map (flxdec->adapter, FlxFrameChunkSize);
      memcpy (&flxfh, data, FlxFrameChunkSize);
      FLX_FRAME_CHUNK_FIX_ENDIANNESS (&flxfh);
      gst_adapter_unmap (flxdec->adapter);

      switch (flxfh.id) {
        case FLX_FRAME_TYPE:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          /* flush header */
          gst_adapter_flush (flxdec->adapter, FlxFrameChunkSize);

          chunk = gst_adapter_take (flxdec->adapter,
              flxfh.size - FlxFrameChunkSize);
          FLX_FRAME_TYPE_FIX_ENDIANNESS ((FlxFrameType *) chunk);
          if (((FlxFrameType *) chunk)->chunks == 0)
            break;

          /* create 32 bits output frame */
//          res = gst_pad_alloc_buffer_and_set_caps (flxdec->srcpad,
//              GST_BUFFER_OFFSET_NONE,
//              flxdec->size * 4, GST_PAD_CAPS (flxdec->srcpad), &out);
//          if (res != GST_FLOW_OK)
//            break;

          out = gst_buffer_new_and_alloc (flxdec->size * 4);

          /* decode chunks */
          if (!flx_decode_chunks (flxdec,
                  ((FlxFrameType *) chunk)->chunks,
                  chunk + FlxFrameTypeSize, flxdec->frame_data)) {
            GST_ELEMENT_ERROR (flxdec, STREAM, DECODE,
                ("%s", "Could not decode chunk"), NULL);
            return GST_FLOW_ERROR;
          }

          /* save copy of the current frame for possible delta. */
          memcpy (flxdec->delta_data, flxdec->frame_data, flxdec->size);

          gst_buffer_map (out, &map, GST_MAP_WRITE);
          /* convert current frame. */
          flx_colorspace_convert (flxdec->converter, flxdec->frame_data,
              map.data);
          gst_buffer_unmap (out, &map);

          GST_BUFFER_TIMESTAMP (out) = flxdec->next_time;
          flxdec->next_time += flxdec->frame_time;

          res = gst_pad_push (flxdec->srcpad, out);
          break;
        default:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          gst_adapter_flush (flxdec->adapter, flxfh.size);
          break;
      }

      g_free (chunk);

      avail = gst_adapter_available (flxdec->adapter);
    }
  }
need_more_data:
  return res;

  /* ERRORS */
wrong_type:
  {
    GST_ELEMENT_ERROR (flxdec, STREAM, WRONG_TYPE, (NULL),
        ("not a flx file (type %x)", flxh->type));
    gst_object_unref (flxdec);
    return GST_FLOW_ERROR;
  }
}

The gst_decode_chain_free_internal function in the flxdex decoder in gst-plugins-good in GStreamer before 1.10.2 allows remote attackers to cause a denial of service (invalid memory read and crash) via an invalid file, which triggers an incorrect unref call.


gst_flxdec_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
{
  GstCaps *caps;
  guint avail;
  GstFlowReturn res = GST_FLOW_OK;

  GstFlxDec *flxdec;
  FlxHeader *flxh;

  g_return_val_if_fail (buf != NULL, GST_FLOW_ERROR);
  flxdec = (GstFlxDec *) parent;
  g_return_val_if_fail (flxdec != NULL, GST_FLOW_ERROR);

  gst_adapter_push (flxdec->adapter, buf);
  avail = gst_adapter_available (flxdec->adapter);

  if (flxdec->state == GST_FLXDEC_READ_HEADER) {
    if (avail >= FlxHeaderSize) {
      const guint8 *data = gst_adapter_map (flxdec->adapter, FlxHeaderSize);
      GstCaps *templ;

      memcpy ((gchar *) & flxdec->hdr, data, FlxHeaderSize);
      FLX_HDR_FIX_ENDIANNESS (&(flxdec->hdr));
      gst_adapter_unmap (flxdec->adapter);
      gst_adapter_flush (flxdec->adapter, FlxHeaderSize);

      flxh = &flxdec->hdr;

      /* check header */
      if (flxh->type != FLX_MAGICHDR_FLI &&
          flxh->type != FLX_MAGICHDR_FLC && flxh->type != FLX_MAGICHDR_FLX)
        goto wrong_type;

      GST_LOG ("size      :  %d", flxh->size);
      GST_LOG ("frames    :  %d", flxh->frames);
      GST_LOG ("width     :  %d", flxh->width);
      GST_LOG ("height    :  %d", flxh->height);
      GST_LOG ("depth     :  %d", flxh->depth);
      GST_LOG ("speed     :  %d", flxh->speed);

      flxdec->next_time = 0;

      if (flxh->type == FLX_MAGICHDR_FLI) {
        flxdec->frame_time = JIFFIE * flxh->speed;
      } else if (flxh->speed == 0) {
        flxdec->frame_time = GST_SECOND / 70;
      } else {
        flxdec->frame_time = flxh->speed * GST_MSECOND;
      }

      flxdec->duration = flxh->frames * flxdec->frame_time;
      GST_LOG ("duration   :  %" GST_TIME_FORMAT,
          GST_TIME_ARGS (flxdec->duration));

      templ = gst_pad_get_pad_template_caps (flxdec->srcpad);
      caps = gst_caps_copy (templ);
      gst_caps_unref (templ);
      gst_caps_set_simple (caps,
          "width", G_TYPE_INT, flxh->width,
          "height", G_TYPE_INT, flxh->height,
          "framerate", GST_TYPE_FRACTION, (gint) GST_MSECOND,
          (gint) flxdec->frame_time / 1000, NULL);

      gst_pad_set_caps (flxdec->srcpad, caps);
      gst_caps_unref (caps);

      if (flxh->depth <= 8)
        flxdec->converter =
            flx_colorspace_converter_new (flxh->width, flxh->height);

      if (flxh->type == FLX_MAGICHDR_FLC || flxh->type == FLX_MAGICHDR_FLX) {
        GST_LOG ("(FLC) aspect_dx :  %d", flxh->aspect_dx);
        GST_LOG ("(FLC) aspect_dy :  %d", flxh->aspect_dy);
        GST_LOG ("(FLC) oframe1   :  0x%08x", flxh->oframe1);
        GST_LOG ("(FLC) oframe2   :  0x%08x", flxh->oframe2);
      }

      flxdec->size = ((guint) flxh->width * (guint) flxh->height);

      /* create delta and output frame */
      flxdec->frame_data = g_malloc (flxdec->size);
      flxdec->delta_data = g_malloc (flxdec->size);

      flxdec->state = GST_FLXDEC_PLAYING;
    }
  } else if (flxdec->state == GST_FLXDEC_PLAYING) {
    GstBuffer *out;

    /* while we have enough data in the adapter */
    while (avail >= FlxFrameChunkSize && res == GST_FLOW_OK) {
      FlxFrameChunk flxfh;
      guchar *chunk;
      const guint8 *data;
      GstMapInfo map;

      chunk = NULL;
      data = gst_adapter_map (flxdec->adapter, FlxFrameChunkSize);
      memcpy (&flxfh, data, FlxFrameChunkSize);
      FLX_FRAME_CHUNK_FIX_ENDIANNESS (&flxfh);
      gst_adapter_unmap (flxdec->adapter);

      switch (flxfh.id) {
        case FLX_FRAME_TYPE:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          /* flush header */
          gst_adapter_flush (flxdec->adapter, FlxFrameChunkSize);

          chunk = gst_adapter_take (flxdec->adapter,
              flxfh.size - FlxFrameChunkSize);
          FLX_FRAME_TYPE_FIX_ENDIANNESS ((FlxFrameType *) chunk);
          if (((FlxFrameType *) chunk)->chunks == 0)
            break;

          /* create 32 bits output frame */
//          res = gst_pad_alloc_buffer_and_set_caps (flxdec->srcpad,
//              GST_BUFFER_OFFSET_NONE,
//              flxdec->size * 4, GST_PAD_CAPS (flxdec->srcpad), &out);
//          if (res != GST_FLOW_OK)
//            break;

          out = gst_buffer_new_and_alloc (flxdec->size * 4);

          /* decode chunks */
          if (!flx_decode_chunks (flxdec,
                  ((FlxFrameType *) chunk)->chunks,
                  chunk + FlxFrameTypeSize, flxdec->frame_data)) {
            GST_ELEMENT_ERROR (flxdec, STREAM, DECODE,
                ("%s", "Could not decode chunk"), NULL);
            return GST_FLOW_ERROR;
          }

          /* save copy of the current frame for possible delta. */
          memcpy (flxdec->delta_data, flxdec->frame_data, flxdec->size);

          gst_buffer_map (out, &map, GST_MAP_WRITE);
          /* convert current frame. */
          flx_colorspace_convert (flxdec->converter, flxdec->frame_data,
              map.data);
          gst_buffer_unmap (out, &map);

          GST_BUFFER_TIMESTAMP (out) = flxdec->next_time;
          flxdec->next_time += flxdec->frame_time;

          res = gst_pad_push (flxdec->srcpad, out);
          break;
        default:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          gst_adapter_flush (flxdec->adapter, flxfh.size);
          break;
      }

      g_free (chunk);

      avail = gst_adapter_available (flxdec->adapter);
    }
  }
need_more_data:
  return res;

  /* ERRORS */
wrong_type:
  {
    GST_ELEMENT_ERROR (flxdec, STREAM, WRONG_TYPE, (NULL),
        ("not a flx file (type %x)", flxh->type));
    return GST_FLOW_ERROR;
  }
}


cgroup-v1: Require capabilities to set release_agent

The cgroup release_agent is called with call_usermodehelper.  The function
call_usermodehelper starts the release_agent with a full set fo capabilities.
Therefore require capabilities when setting the release_agaent.

Reported-by: Tabitha Sable <tabitha.c.sable@gmail.com>
Tested-by: Tabitha Sable <tabitha.c.sable@gmail.com>
Fixes: 81a6a5cdd2c5 ("Task Control Groups: automatic userspace notification of idle cgroups")
Cc: stable@vger.kernel.org # v2.6.24+
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
					  char *buf, size_t nbytes, loff_t off)
{
	struct cgroup *cgrp;

	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);

	cgrp = cgroup_kn_lock_live(of->kn, false);
	if (!cgrp)
		return -ENODEV;
	spin_lock(&release_agent_path_lock);
	strlcpy(cgrp->root->release_agent_path, strstrip(buf),
		sizeof(cgrp->root->release_agent_path));
	spin_unlock(&release_agent_path_lock);
	cgroup_kn_unlock(of->kn);
	return nbytes;
}

A vulnerability was found in the Linux kernel’s cgroup_release_agent_write in the kernel/cgroup/cgroup-v1.c function. This flaw, under certain circumstances, allows the use of the cgroups v1 release_agent feature to escalate privileges and bypass the namespace isolation unexpectedly.


static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
					  char *buf, size_t nbytes, loff_t off)
{
	struct cgroup *cgrp;

	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);

	/*
	 * Release agent gets called with all capabilities,
	 * require capabilities to set release agent.
	 */
	if ((of->file->f_cred->user_ns != &init_user_ns) ||
	    !capable(CAP_SYS_ADMIN))
		return -EPERM;

	cgrp = cgroup_kn_lock_live(of->kn, false);
	if (!cgrp)
		return -ENODEV;
	spin_lock(&release_agent_path_lock);
	strlcpy(cgrp->root->release_agent_path, strstrip(buf),
		sizeof(cgrp->root->release_agent_path));
	spin_unlock(&release_agent_path_lock);
	cgroup_kn_unlock(of->kn);
	return nbytes;
}


SERVER-59071 Treat '$sample' as unsharded when connecting directly to shards

(cherry picked from commit f3604b901d688c194de5e430c7fbab060c9dc8e0)

createRandomCursorExecutor(const CollectionPtr& coll,
                           const boost::intrusive_ptr<ExpressionContext>& expCtx,
                           long long sampleSize,
                           long long numRecords,
                           boost::optional<BucketUnpacker> bucketUnpacker) {
    OperationContext* opCtx = expCtx->opCtx;

    // Verify that we are already under a collection lock. We avoid taking locks ourselves in this
    // function because double-locking forces any PlanExecutor we create to adopt a NO_YIELD policy.
    invariant(opCtx->lockState()->isCollectionLockedForMode(coll->ns(), MODE_IS));

    static const double kMaxSampleRatioForRandCursor = 0.05;
    if (!expCtx->ns.isTimeseriesBucketsCollection()) {
        if (sampleSize > numRecords * kMaxSampleRatioForRandCursor || numRecords <= 100) {
            return std::pair{nullptr, false};
        }
    } else {
        // Suppose that a time-series bucket collection is observed to contain 200 buckets, and the
        // 'gTimeseriesBucketMaxCount' parameter is set to 1000. If all buckets are full, then the
        // maximum possible measurment count would be 200 * 1000 = 200,000. While the
        // 'SampleFromTimeseriesBucket' plan is more efficient when the sample size is small
        // relative to the total number of measurements in the time-series collection, for larger
        // sample sizes the top-k sort based sample is faster. Experiments have approximated that
        // the tipping point is roughly when the requested sample size is greater than 1% of the
        // maximum possible number of measurements in the collection (i.e. numBuckets *
        // maxMeasurementsPerBucket).
        static const double kCoefficient = 0.01;
        if (sampleSize > kCoefficient * numRecords * gTimeseriesBucketMaxCount) {
            return std::pair{nullptr, false};
        }
    }

    // Attempt to get a random cursor from the RecordStore.
    auto rsRandCursor = coll->getRecordStore()->getRandomCursor(opCtx);
    if (!rsRandCursor) {
        // The storage engine has no random cursor support.
        return std::pair{nullptr, false};
    }

    // Build a MultiIteratorStage and pass it the random-sampling RecordCursor.
    auto ws = std::make_unique<WorkingSet>();
    std::unique_ptr<PlanStage> root =
        std::make_unique<MultiIteratorStage>(expCtx.get(), ws.get(), coll);
    static_cast<MultiIteratorStage*>(root.get())->addIterator(std::move(rsRandCursor));

    // If the incoming operation is sharded, use the CSS to infer the filtering metadata for the
    // collection, otherwise treat it as unsharded
    auto collectionFilter =
        CollectionShardingState::get(opCtx, coll->ns())
            ->getOwnershipFilter(
                opCtx, CollectionShardingState::OrphanCleanupPolicy::kDisallowOrphanCleanup);

    TrialStage* trialStage = nullptr;

    // Because 'numRecords' includes orphan documents, our initial decision to optimize the $sample
    // cursor may have been mistaken. For sharded collections, build a TRIAL plan that will switch
    // to a collection scan if the ratio of orphaned to owned documents encountered over the first
    // 100 works() is such that we would have chosen not to optimize.
    static const size_t kMaxPresampleSize = 100;
    if (collectionFilter.isSharded() && !expCtx->ns.isTimeseriesBucketsCollection()) {
        // The ratio of owned to orphaned documents must be at least equal to the ratio between the
        // requested sampleSize and the maximum permitted sampleSize for the original constraints to
        // be satisfied. For instance, if there are 200 documents and the sampleSize is 5, then at
        // least (5 / (200*0.05)) = (5/10) = 50% of those documents must be owned. If less than 5%
        // of the documents in the collection are owned, we default to the backup plan.
        const auto minAdvancedToWorkRatio = std::max(
            sampleSize / (numRecords * kMaxSampleRatioForRandCursor), kMaxSampleRatioForRandCursor);
        // The trial plan is SHARDING_FILTER-MULTI_ITERATOR.
        auto randomCursorPlan = std::make_unique<ShardFilterStage>(
            expCtx.get(), collectionFilter, ws.get(), std::move(root));
        // The backup plan is SHARDING_FILTER-COLLSCAN.
        std::unique_ptr<PlanStage> collScanPlan = std::make_unique<CollectionScan>(
            expCtx.get(), coll, CollectionScanParams{}, ws.get(), nullptr);
        collScanPlan = std::make_unique<ShardFilterStage>(
            expCtx.get(), collectionFilter, ws.get(), std::move(collScanPlan));
        // Place a TRIAL stage at the root of the plan tree, and pass it the trial and backup plans.
        root = std::make_unique<TrialStage>(expCtx.get(),
                                            ws.get(),
                                            std::move(randomCursorPlan),
                                            std::move(collScanPlan),
                                            kMaxPresampleSize,
                                            minAdvancedToWorkRatio);
        trialStage = static_cast<TrialStage*>(root.get());
    } else if (expCtx->ns.isTimeseriesBucketsCollection()) {
        // Use a 'TrialStage' to run a trial between 'SampleFromTimeseriesBucket' and
        // 'UnpackTimeseriesBucket' with $sample left in the pipeline in-place. If the buckets are
        // not sufficiently full, or the 'SampleFromTimeseriesBucket' plan draws too many
        // duplicates, then we will fall back to the 'TrialStage' backup plan. This backup plan uses
        // the top-k sort sampling approach.
        //
        // Suppose the 'gTimeseriesBucketMaxCount' is 1000, but each bucket only contains 500
        // documents on average. The observed trial advanced/work ratio approximates the average
        // bucket fullness, noted here as "abf". In this example, abf = 500 / 1000 = 0.5.
        // Experiments have shown that the optimized 'SampleFromTimeseriesBucket' algorithm performs
        // better than backup plan when
        //
        //     sampleSize < 0.02 * abf * numRecords * gTimeseriesBucketMaxCount
        //
        //  This inequality can be rewritten as
        //
        //     abf > sampleSize / (0.02 * numRecords * gTimeseriesBucketMaxCount)
        //
        // Therefore, if the advanced/work ratio exceeds this threshold, we will use the
        // 'SampleFromTimeseriesBucket' plan. Note that as the sample size requested by the user
        // becomes larger with respect to the number of buckets, we require a higher advanced/work
        // ratio in order to justify using 'SampleFromTimeseriesBucket'.
        //
        // Additionally, we require the 'TrialStage' to approximate the abf as at least 0.25. When
        // buckets are mostly empty, the 'SampleFromTimeseriesBucket' will be inefficient due to a
        // lot of sampling "misses".
        static const auto kCoefficient = 0.02;
        static const auto kMinBucketFullness = 0.25;
        const auto minAdvancedToWorkRatio = std::max(
            std::min(sampleSize / (kCoefficient * numRecords * gTimeseriesBucketMaxCount), 1.0),
            kMinBucketFullness);

        auto arhashPlan = std::make_unique<SampleFromTimeseriesBucket>(
            expCtx.get(),
            ws.get(),
            std::move(root),
            *bucketUnpacker,
            // By using a quantity slightly higher than 'kMaxPresampleSize', we ensure that the
            // 'SampleFromTimeseriesBucket' stage won't fail due to too many consecutive sampling
            // attempts during the 'TrialStage's trial period.
            kMaxPresampleSize + 5,
            sampleSize,
            gTimeseriesBucketMaxCount);

        std::unique_ptr<PlanStage> collScanPlan = std::make_unique<CollectionScan>(
            expCtx.get(), coll, CollectionScanParams{}, ws.get(), nullptr);

        auto topkSortPlan = std::make_unique<UnpackTimeseriesBucket>(
            expCtx.get(), ws.get(), std::move(collScanPlan), *bucketUnpacker);

        root = std::make_unique<TrialStage>(expCtx.get(),
                                            ws.get(),
                                            std::move(arhashPlan),
                                            std::move(topkSortPlan),
                                            kMaxPresampleSize,
                                            minAdvancedToWorkRatio);
        trialStage = static_cast<TrialStage*>(root.get());
    }

    auto execStatus = plan_executor_factory::make(expCtx,
                                                  std::move(ws),
                                                  std::move(root),
                                                  &coll,
                                                  opCtx->inMultiDocumentTransaction()
                                                      ? PlanYieldPolicy::YieldPolicy::INTERRUPT_ONLY
                                                      : PlanYieldPolicy::YieldPolicy::YIELD_AUTO,
                                                  QueryPlannerParams::RETURN_OWNED_DATA);
    if (!execStatus.isOK()) {
        return execStatus.getStatus();
    }

    // For sharded collections, the root of the plan tree is a TrialStage that may have chosen
    // either a random-sampling cursor trial plan or a COLLSCAN backup plan. We can only optimize
    // the $sample aggregation stage if the trial plan was chosen.
    return std::pair{std::move(execStatus.getValue()),
                     !trialStage || !trialStage->pickedBackupPlan()};
}

An authorized user may trigger an invariant which may result in denial of service or server exit if a relevant aggregation request is sent to a shard. Usually, the requests are sent via mongos and special privileges are required in order to know the address of the shards and to log in to the shards of an auth enabled environment.


createRandomCursorExecutor(const CollectionPtr& coll,
                           const boost::intrusive_ptr<ExpressionContext>& expCtx,
                           long long sampleSize,
                           long long numRecords,
                           boost::optional<BucketUnpacker> bucketUnpacker) {
    OperationContext* opCtx = expCtx->opCtx;

    // Verify that we are already under a collection lock. We avoid taking locks ourselves in this
    // function because double-locking forces any PlanExecutor we create to adopt a NO_YIELD policy.
    invariant(opCtx->lockState()->isCollectionLockedForMode(coll->ns(), MODE_IS));

    static const double kMaxSampleRatioForRandCursor = 0.05;
    if (!expCtx->ns.isTimeseriesBucketsCollection()) {
        if (sampleSize > numRecords * kMaxSampleRatioForRandCursor || numRecords <= 100) {
            return std::pair{nullptr, false};
        }
    } else {
        // Suppose that a time-series bucket collection is observed to contain 200 buckets, and the
        // 'gTimeseriesBucketMaxCount' parameter is set to 1000. If all buckets are full, then the
        // maximum possible measurment count would be 200 * 1000 = 200,000. While the
        // 'SampleFromTimeseriesBucket' plan is more efficient when the sample size is small
        // relative to the total number of measurements in the time-series collection, for larger
        // sample sizes the top-k sort based sample is faster. Experiments have approximated that
        // the tipping point is roughly when the requested sample size is greater than 1% of the
        // maximum possible number of measurements in the collection (i.e. numBuckets *
        // maxMeasurementsPerBucket).
        static const double kCoefficient = 0.01;
        if (sampleSize > kCoefficient * numRecords * gTimeseriesBucketMaxCount) {
            return std::pair{nullptr, false};
        }
    }

    // Attempt to get a random cursor from the RecordStore.
    auto rsRandCursor = coll->getRecordStore()->getRandomCursor(opCtx);
    if (!rsRandCursor) {
        // The storage engine has no random cursor support.
        return std::pair{nullptr, false};
    }

    // Build a MultiIteratorStage and pass it the random-sampling RecordCursor.
    auto ws = std::make_unique<WorkingSet>();
    std::unique_ptr<PlanStage> root =
        std::make_unique<MultiIteratorStage>(expCtx.get(), ws.get(), coll);
    static_cast<MultiIteratorStage*>(root.get())->addIterator(std::move(rsRandCursor));

    TrialStage* trialStage = nullptr;

    // Because 'numRecords' includes orphan documents, our initial decision to optimize the $sample
    // cursor may have been mistaken. For sharded collections, build a TRIAL plan that will switch
    // to a collection scan if the ratio of orphaned to owned documents encountered over the first
    // 100 works() is such that we would have chosen not to optimize.
    static const size_t kMaxPresampleSize = 100;
    if (auto css = CollectionShardingState::get(opCtx, coll->ns());
        css->getCollectionDescription(opCtx).isSharded() &&
        !expCtx->ns.isTimeseriesBucketsCollection()) {
        // The ratio of owned to orphaned documents must be at least equal to the ratio between the
        // requested sampleSize and the maximum permitted sampleSize for the original constraints to
        // be satisfied. For instance, if there are 200 documents and the sampleSize is 5, then at
        // least (5 / (200*0.05)) = (5/10) = 50% of those documents must be owned. If less than 5%
        // of the documents in the collection are owned, we default to the backup plan.
        const auto minAdvancedToWorkRatio = std::max(
            sampleSize / (numRecords * kMaxSampleRatioForRandCursor), kMaxSampleRatioForRandCursor);
        // Since the incoming operation is sharded, use the CSS to infer the filtering metadata for
        // the collection. We get the shard ownership filter after checking to see if the collection
        // is sharded to avoid an invariant from being fired in this call.
        auto collectionFilter = css->getOwnershipFilter(
            opCtx, CollectionShardingState::OrphanCleanupPolicy::kDisallowOrphanCleanup);
        // The trial plan is SHARDING_FILTER-MULTI_ITERATOR.
        auto randomCursorPlan = std::make_unique<ShardFilterStage>(
            expCtx.get(), collectionFilter, ws.get(), std::move(root));
        // The backup plan is SHARDING_FILTER-COLLSCAN.
        std::unique_ptr<PlanStage> collScanPlan = std::make_unique<CollectionScan>(
            expCtx.get(), coll, CollectionScanParams{}, ws.get(), nullptr);
        collScanPlan = std::make_unique<ShardFilterStage>(
            expCtx.get(), collectionFilter, ws.get(), std::move(collScanPlan));
        // Place a TRIAL stage at the root of the plan tree, and pass it the trial and backup plans.
        root = std::make_unique<TrialStage>(expCtx.get(),
                                            ws.get(),
                                            std::move(randomCursorPlan),
                                            std::move(collScanPlan),
                                            kMaxPresampleSize,
                                            minAdvancedToWorkRatio);
        trialStage = static_cast<TrialStage*>(root.get());
    } else if (expCtx->ns.isTimeseriesBucketsCollection()) {
        // Use a 'TrialStage' to run a trial between 'SampleFromTimeseriesBucket' and
        // 'UnpackTimeseriesBucket' with $sample left in the pipeline in-place. If the buckets are
        // not sufficiently full, or the 'SampleFromTimeseriesBucket' plan draws too many
        // duplicates, then we will fall back to the 'TrialStage' backup plan. This backup plan uses
        // the top-k sort sampling approach.
        //
        // Suppose the 'gTimeseriesBucketMaxCount' is 1000, but each bucket only contains 500
        // documents on average. The observed trial advanced/work ratio approximates the average
        // bucket fullness, noted here as "abf". In this example, abf = 500 / 1000 = 0.5.
        // Experiments have shown that the optimized 'SampleFromTimeseriesBucket' algorithm performs
        // better than backup plan when
        //
        //     sampleSize < 0.02 * abf * numRecords * gTimeseriesBucketMaxCount
        //
        //  This inequality can be rewritten as
        //
        //     abf > sampleSize / (0.02 * numRecords * gTimeseriesBucketMaxCount)
        //
        // Therefore, if the advanced/work ratio exceeds this threshold, we will use the
        // 'SampleFromTimeseriesBucket' plan. Note that as the sample size requested by the user
        // becomes larger with respect to the number of buckets, we require a higher advanced/work
        // ratio in order to justify using 'SampleFromTimeseriesBucket'.
        //
        // Additionally, we require the 'TrialStage' to approximate the abf as at least 0.25. When
        // buckets are mostly empty, the 'SampleFromTimeseriesBucket' will be inefficient due to a
        // lot of sampling "misses".
        static const auto kCoefficient = 0.02;
        static const auto kMinBucketFullness = 0.25;
        const auto minAdvancedToWorkRatio = std::max(
            std::min(sampleSize / (kCoefficient * numRecords * gTimeseriesBucketMaxCount), 1.0),
            kMinBucketFullness);

        auto arhashPlan = std::make_unique<SampleFromTimeseriesBucket>(
            expCtx.get(),
            ws.get(),
            std::move(root),
            *bucketUnpacker,
            // By using a quantity slightly higher than 'kMaxPresampleSize', we ensure that the
            // 'SampleFromTimeseriesBucket' stage won't fail due to too many consecutive sampling
            // attempts during the 'TrialStage's trial period.
            kMaxPresampleSize + 5,
            sampleSize,
            gTimeseriesBucketMaxCount);

        std::unique_ptr<PlanStage> collScanPlan = std::make_unique<CollectionScan>(
            expCtx.get(), coll, CollectionScanParams{}, ws.get(), nullptr);

        auto topkSortPlan = std::make_unique<UnpackTimeseriesBucket>(
            expCtx.get(), ws.get(), std::move(collScanPlan), *bucketUnpacker);

        root = std::make_unique<TrialStage>(expCtx.get(),
                                            ws.get(),
                                            std::move(arhashPlan),
                                            std::move(topkSortPlan),
                                            kMaxPresampleSize,
                                            minAdvancedToWorkRatio);
        trialStage = static_cast<TrialStage*>(root.get());
    }

    auto execStatus = plan_executor_factory::make(expCtx,
                                                  std::move(ws),
                                                  std::move(root),
                                                  &coll,
                                                  opCtx->inMultiDocumentTransaction()
                                                      ? PlanYieldPolicy::YieldPolicy::INTERRUPT_ONLY
                                                      : PlanYieldPolicy::YieldPolicy::YIELD_AUTO,
                                                  QueryPlannerParams::RETURN_OWNED_DATA);
    if (!execStatus.isOK()) {
        return execStatus.getStatus();
    }

    // For sharded collections, the root of the plan tree is a TrialStage that may have chosen
    // either a random-sampling cursor trial plan or a COLLSCAN backup plan. We can only optimize
    // the $sample aggregation stage if the trial plan was chosen.
    return std::pair{std::move(execStatus.getValue()),
                     !trialStage || !trialStage->pickedBackupPlan()};
}


fix(plugin): Add default limits for chunks and message size

Based on a reported DoS vulnerability reported by Team82 (Claroty
Research).

setup_secureChannel(void) {
    TestingPolicy(&dummyPolicy, dummyCertificate, &fCalled, &keySizes);
    UA_SecureChannel_init(&testChannel, &UA_ConnectionConfig_default);
    UA_SecureChannel_setSecurityPolicy(&testChannel, &dummyPolicy, &dummyCertificate);

    testingConnection = createDummyConnection(65535, &sentData);
    UA_Connection_attachSecureChannel(&testingConnection, &testChannel);
    testChannel.connection = &testingConnection;

    testChannel.state = UA_SECURECHANNELSTATE_OPEN;
}

The package open62541/open62541 before 1.2.5, from 1.3-rc1 and before 1.3.1 are vulnerable to Denial of Service (DoS) due to a missing limitation on the number of received chunks - per single session or in total for all concurrent sessions. An attacker can exploit this vulnerability by sending an unlimited number of huge chunks (e.g. 2GB each) without sending the Final closing chunk.


setup_secureChannel(void) {
    TestingPolicy(&dummyPolicy, dummyCertificate, &fCalled, &keySizes);
    UA_SecureChannel_init(&testChannel, &UA_ConnectionConfig_default);
    UA_SecureChannel_setSecurityPolicy(&testChannel, &dummyPolicy, &dummyCertificate);

    testingConnection =
        createDummyConnection(UA_ConnectionConfig_default.sendBufferSize, &sentData);
    UA_Connection_attachSecureChannel(&testingConnection, &testChannel);
    testChannel.connection = &testingConnection;

    testChannel.state = UA_SECURECHANNELSTATE_OPEN;
}


void mobi_buffer_move(MOBIBuffer *buf, const int offset, const size_t len) {
    size_t aoffset = (size_t) abs(offset);
    unsigned char *source = buf->data + buf->offset;
    if (offset >= 0) {
        if (buf->offset + aoffset + len > buf->maxlen) {
            debug_print("%s", "End of buffer\n");
            buf->error = MOBI_BUFFER_END;
            return;
        }
        source += aoffset;
    } else {
        if (buf->offset < aoffset) {
            debug_print("%s", "End of buffer\n");
            buf->error = MOBI_BUFFER_END;
            return;
        }
        source -= aoffset;
    }
    memmove(buf->data + buf->offset, source, len);
    buf->offset += len;
}

libmobi is vulnerable to Out-of-bounds Write


void mobi_buffer_move(MOBIBuffer *buf, const int offset, const size_t len) {
    size_t aoffset = (size_t) abs(offset);
    unsigned char *source = buf->data + buf->offset;
    if (offset >= 0) {
        if (buf->offset + aoffset + len > buf->maxlen) {
            debug_print("%s", "End of buffer\n");
            buf->error = MOBI_BUFFER_END;
            return;
        }
        source += aoffset;
    } else {
        if ( (buf->offset < aoffset) || (buf->offset + len > buf->maxlen) ) {
            debug_print("%s", "Beyond start/end of buffer\n");
            buf->error = MOBI_BUFFER_END;
            return;
        }
        source -= aoffset;
    }
    memmove(buf->data + buf->offset, source, len);
    buf->offset += len;
}


cadence_gem: switch to use qemu_receive_packet() for loopback

This patch switches to use qemu_receive_packet() which can detect
reentrancy and return early.

This is intended to address CVE-2021-3416.

Cc: Prasad J Pandit <ppandit@redhat.com>
Cc: qemu-stable@nongnu.org
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Jason Wang <jasowang@redhat.com>

static void gem_transmit(CadenceGEMState *s)
{
    uint32_t desc[DESC_MAX_NUM_WORDS];
    hwaddr packet_desc_addr;
    uint8_t     *p;
    unsigned    total_bytes;
    int q = 0;

    /* Do nothing if transmit is not enabled. */
    if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_TXENA)) {
        return;
    }

    DB_PRINT("\n");

    /* The packet we will hand off to QEMU.
     * Packets scattered across multiple descriptors are gathered to this
     * one contiguous buffer first.
     */
    p = s->tx_packet;
    total_bytes = 0;

    for (q = s->num_priority_queues - 1; q >= 0; q--) {
        /* read current descriptor */
        packet_desc_addr = gem_get_tx_desc_addr(s, q);

        DB_PRINT("read descriptor 0x%" HWADDR_PRIx "\n", packet_desc_addr);
        address_space_read(&s->dma_as, packet_desc_addr,
                           MEMTXATTRS_UNSPECIFIED, desc,
                           sizeof(uint32_t) * gem_get_desc_len(s, false));
        /* Handle all descriptors owned by hardware */
        while (tx_desc_get_used(desc) == 0) {

            /* Do nothing if transmit is not enabled. */
            if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_TXENA)) {
                return;
            }
            print_gem_tx_desc(desc, q);

            /* The real hardware would eat this (and possibly crash).
             * For QEMU let's lend a helping hand.
             */
            if ((tx_desc_get_buffer(s, desc) == 0) ||
                (tx_desc_get_length(desc) == 0)) {
                DB_PRINT("Invalid TX descriptor @ 0x%" HWADDR_PRIx "\n",
                         packet_desc_addr);
                break;
            }

            if (tx_desc_get_length(desc) > gem_get_max_buf_len(s, true) -
                                               (p - s->tx_packet)) {
                qemu_log_mask(LOG_GUEST_ERROR, "TX descriptor @ 0x%" \
                         HWADDR_PRIx " too large: size 0x%x space 0x%zx\n",
                         packet_desc_addr, tx_desc_get_length(desc),
                         gem_get_max_buf_len(s, true) - (p - s->tx_packet));
                gem_set_isr(s, q, GEM_INT_AMBA_ERR);
                break;
            }

            /* Gather this fragment of the packet from "dma memory" to our
             * contig buffer.
             */
            address_space_read(&s->dma_as, tx_desc_get_buffer(s, desc),
                               MEMTXATTRS_UNSPECIFIED,
                               p, tx_desc_get_length(desc));
            p += tx_desc_get_length(desc);
            total_bytes += tx_desc_get_length(desc);

            /* Last descriptor for this packet; hand the whole thing off */
            if (tx_desc_get_last(desc)) {
                uint32_t desc_first[DESC_MAX_NUM_WORDS];
                hwaddr desc_addr = gem_get_tx_desc_addr(s, q);

                /* Modify the 1st descriptor of this packet to be owned by
                 * the processor.
                 */
                address_space_read(&s->dma_as, desc_addr,
                                   MEMTXATTRS_UNSPECIFIED, desc_first,
                                   sizeof(desc_first));
                tx_desc_set_used(desc_first);
                address_space_write(&s->dma_as, desc_addr,
                                    MEMTXATTRS_UNSPECIFIED, desc_first,
                                    sizeof(desc_first));
                /* Advance the hardware current descriptor past this packet */
                if (tx_desc_get_wrap(desc)) {
                    s->tx_desc_addr[q] = gem_get_tx_queue_base_addr(s, q);
                } else {
                    s->tx_desc_addr[q] = packet_desc_addr +
                                         4 * gem_get_desc_len(s, false);
                }
                DB_PRINT("TX descriptor next: 0x%08x\n", s->tx_desc_addr[q]);

                s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_TXCMPL;
                gem_set_isr(s, q, GEM_INT_TXCMPL);

                /* Handle interrupt consequences */
                gem_update_int_status(s);

                /* Is checksum offload enabled? */
                if (s->regs[GEM_DMACFG] & GEM_DMACFG_TXCSUM_OFFL) {
                    net_checksum_calculate(s->tx_packet, total_bytes, CSUM_ALL);
                }

                /* Update MAC statistics */
                gem_transmit_updatestats(s, s->tx_packet, total_bytes);

                /* Send the packet somewhere */
                if (s->phy_loop || (s->regs[GEM_NWCTRL] &
                                    GEM_NWCTRL_LOCALLOOP)) {
                    gem_receive(qemu_get_queue(s->nic), s->tx_packet,
                                total_bytes);
                } else {
                    qemu_send_packet(qemu_get_queue(s->nic), s->tx_packet,
                                     total_bytes);
                }

                /* Prepare for next packet */
                p = s->tx_packet;
                total_bytes = 0;
            }

            /* read next descriptor */
            if (tx_desc_get_wrap(desc)) {

                if (s->regs[GEM_DMACFG] & GEM_DMACFG_ADDR_64B) {
                    packet_desc_addr = s->regs[GEM_TBQPH];
                    packet_desc_addr <<= 32;
                } else {
                    packet_desc_addr = 0;
                }
                packet_desc_addr |= gem_get_tx_queue_base_addr(s, q);
            } else {
                packet_desc_addr += 4 * gem_get_desc_len(s, false);
            }
            DB_PRINT("read descriptor 0x%" HWADDR_PRIx "\n", packet_desc_addr);
            address_space_read(&s->dma_as, packet_desc_addr,
                               MEMTXATTRS_UNSPECIFIED, desc,
                               sizeof(uint32_t) * gem_get_desc_len(s, false));
        }

        if (tx_desc_get_used(desc)) {
            s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_USED;
            /* IRQ TXUSED is defined only for queue 0 */
            if (q == 0) {
                gem_set_isr(s, 0, GEM_INT_TXUSED);
            }
            gem_update_int_status(s);
        }
    }
}

A potential stack overflow via infinite loop issue was found in various NIC emulators of QEMU in versions up to and including 5.2.0. The issue occurs in loopback mode of a NIC wherein reentrant DMA checks get bypassed. A guest user/process may use this flaw to consume CPU cycles or crash the QEMU process on the host resulting in DoS scenario.


static void gem_transmit(CadenceGEMState *s)
{
    uint32_t desc[DESC_MAX_NUM_WORDS];
    hwaddr packet_desc_addr;
    uint8_t     *p;
    unsigned    total_bytes;
    int q = 0;

    /* Do nothing if transmit is not enabled. */
    if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_TXENA)) {
        return;
    }

    DB_PRINT("\n");

    /* The packet we will hand off to QEMU.
     * Packets scattered across multiple descriptors are gathered to this
     * one contiguous buffer first.
     */
    p = s->tx_packet;
    total_bytes = 0;

    for (q = s->num_priority_queues - 1; q >= 0; q--) {
        /* read current descriptor */
        packet_desc_addr = gem_get_tx_desc_addr(s, q);

        DB_PRINT("read descriptor 0x%" HWADDR_PRIx "\n", packet_desc_addr);
        address_space_read(&s->dma_as, packet_desc_addr,
                           MEMTXATTRS_UNSPECIFIED, desc,
                           sizeof(uint32_t) * gem_get_desc_len(s, false));
        /* Handle all descriptors owned by hardware */
        while (tx_desc_get_used(desc) == 0) {

            /* Do nothing if transmit is not enabled. */
            if (!(s->regs[GEM_NWCTRL] & GEM_NWCTRL_TXENA)) {
                return;
            }
            print_gem_tx_desc(desc, q);

            /* The real hardware would eat this (and possibly crash).
             * For QEMU let's lend a helping hand.
             */
            if ((tx_desc_get_buffer(s, desc) == 0) ||
                (tx_desc_get_length(desc) == 0)) {
                DB_PRINT("Invalid TX descriptor @ 0x%" HWADDR_PRIx "\n",
                         packet_desc_addr);
                break;
            }

            if (tx_desc_get_length(desc) > gem_get_max_buf_len(s, true) -
                                               (p - s->tx_packet)) {
                qemu_log_mask(LOG_GUEST_ERROR, "TX descriptor @ 0x%" \
                         HWADDR_PRIx " too large: size 0x%x space 0x%zx\n",
                         packet_desc_addr, tx_desc_get_length(desc),
                         gem_get_max_buf_len(s, true) - (p - s->tx_packet));
                gem_set_isr(s, q, GEM_INT_AMBA_ERR);
                break;
            }

            /* Gather this fragment of the packet from "dma memory" to our
             * contig buffer.
             */
            address_space_read(&s->dma_as, tx_desc_get_buffer(s, desc),
                               MEMTXATTRS_UNSPECIFIED,
                               p, tx_desc_get_length(desc));
            p += tx_desc_get_length(desc);
            total_bytes += tx_desc_get_length(desc);

            /* Last descriptor for this packet; hand the whole thing off */
            if (tx_desc_get_last(desc)) {
                uint32_t desc_first[DESC_MAX_NUM_WORDS];
                hwaddr desc_addr = gem_get_tx_desc_addr(s, q);

                /* Modify the 1st descriptor of this packet to be owned by
                 * the processor.
                 */
                address_space_read(&s->dma_as, desc_addr,
                                   MEMTXATTRS_UNSPECIFIED, desc_first,
                                   sizeof(desc_first));
                tx_desc_set_used(desc_first);
                address_space_write(&s->dma_as, desc_addr,
                                    MEMTXATTRS_UNSPECIFIED, desc_first,
                                    sizeof(desc_first));
                /* Advance the hardware current descriptor past this packet */
                if (tx_desc_get_wrap(desc)) {
                    s->tx_desc_addr[q] = gem_get_tx_queue_base_addr(s, q);
                } else {
                    s->tx_desc_addr[q] = packet_desc_addr +
                                         4 * gem_get_desc_len(s, false);
                }
                DB_PRINT("TX descriptor next: 0x%08x\n", s->tx_desc_addr[q]);

                s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_TXCMPL;
                gem_set_isr(s, q, GEM_INT_TXCMPL);

                /* Handle interrupt consequences */
                gem_update_int_status(s);

                /* Is checksum offload enabled? */
                if (s->regs[GEM_DMACFG] & GEM_DMACFG_TXCSUM_OFFL) {
                    net_checksum_calculate(s->tx_packet, total_bytes, CSUM_ALL);
                }

                /* Update MAC statistics */
                gem_transmit_updatestats(s, s->tx_packet, total_bytes);

                /* Send the packet somewhere */
                if (s->phy_loop || (s->regs[GEM_NWCTRL] &
                                    GEM_NWCTRL_LOCALLOOP)) {
                    qemu_receive_packet(qemu_get_queue(s->nic), s->tx_packet,
                                        total_bytes);
                } else {
                    qemu_send_packet(qemu_get_queue(s->nic), s->tx_packet,
                                     total_bytes);
                }

                /* Prepare for next packet */
                p = s->tx_packet;
                total_bytes = 0;
            }

            /* read next descriptor */
            if (tx_desc_get_wrap(desc)) {

                if (s->regs[GEM_DMACFG] & GEM_DMACFG_ADDR_64B) {
                    packet_desc_addr = s->regs[GEM_TBQPH];
                    packet_desc_addr <<= 32;
                } else {
                    packet_desc_addr = 0;
                }
                packet_desc_addr |= gem_get_tx_queue_base_addr(s, q);
            } else {
                packet_desc_addr += 4 * gem_get_desc_len(s, false);
            }
            DB_PRINT("read descriptor 0x%" HWADDR_PRIx "\n", packet_desc_addr);
            address_space_read(&s->dma_as, packet_desc_addr,
                               MEMTXATTRS_UNSPECIFIED, desc,
                               sizeof(uint32_t) * gem_get_desc_len(s, false));
        }

        if (tx_desc_get_used(desc)) {
            s->regs[GEM_TXSTATUS] |= GEM_TXSTATUS_USED;
            /* IRQ TXUSED is defined only for queue 0 */
            if (q == 0) {
                gem_set_isr(s, 0, GEM_INT_TXUSED);
            }
            gem_update_int_status(s);
        }
    }
}