Hello Michael S. Tsirkin,
The patch 6c8e5f3c41c8: "virtio_net: rework mergeable buffer
handling" from Mar 6, 2017, leads to the following static checker
warning:
drivers/net/virtio_net.c:1042 virtnet_receive()
error: uninitialized symbol 'ctx'.
drivers/net/virtio_net.c
1030 static int virtnet_receive(struct receive_queue *rq, int budget)
1031 {
1032 struct virtnet_info *vi = rq->vq->vdev->priv;
1033 unsigned int len, received = 0, bytes = 0;
1034 void *buf;
1035 struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
1036
1037 if (vi->mergeable_rx_bufs) {
1038 void *ctx;
^^^
1039
1040 while (received < budget &&
1041 (buf = virtqueue_get_buf_ctx(rq->vq, &len,
&ctx))) {
^^^^
1042 bytes += receive_buf(vi, rq, buf, len, ctx);
^^^
It's possible that this code is correct, but I looked at it and wasn't
immediately convinced. Returning non-NULL buf is not sufficient to
show that "ctx" is initialized, because if it's vq->indirect then "buf"
is still unintialized. Also it's possible that receive_buf() checks
vq->indirect through some side effect way that I didn't see so it
doesn't use the uninitialized value...
I feel like if this is a false positive, that means the rules are too
subtle... :/
1043 received++;
1044 }
1045 } else {
1046 while (received < budget &&
1047 (buf = virtqueue_get_buf(rq->vq, &len)) != NULL)
{
1048 bytes += receive_buf(vi, rq, buf, len, NULL);
1049 received++;
1050 }
1051 }
1052
regards,
dan carpenter
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