On Mon, 1 Dec 2025 11:41:07 +0800 Edward Adam Davis wrote: > On Fri, 28 Nov 2025 09:39:46 -0800, Jakub Kicinski wrote: > > > In zerocopy_fill_skb_from_iter(), if two copy operations are performed > > > and the first one succeeds while the second one fails, it returns a > > > failure but the count in iterator has already been decremented due to > > > the first successful copy. This ultimately affects the local variable > > > rest_len in virtio_transport_send_pkt_info(), causing the remaining > > > count in rest_len to be greater than the actual iterator count. As a > > > result, packet sending operations continue even when the iterator count > > > is zero, which further leads to skb->len being 0 and triggers the warning > > > reported by syzbot [1]. > > > > Please follow the subsystem guidelines for posting patches: > > https://www.kernel.org/doc/html/next/process/maintainer-netdev.html > > Your patch breaks zerocopy tests. > I see that they all timed out. I'm not familiar with this test, how can > I get more details about it?
IIRC its was the packetdrill tests: tools/testing/selftests/net/packetdrill/tcp_fastopen_server_basic-zero-payload.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_basic.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_batch.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_client.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_closed.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_epoll_edge.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_epoll_exclusive.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_epoll_oneshot.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_fastopen-client.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_fastopen-server.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_maxfrags.pkt tools/testing/selftests/net/packetdrill/tcp_zerocopy_small.pkt If you have the packetdrill command installed those _should_ be relatively easy to run via standard kselftest commands
