6.12-stable review patch. If anyone has any objections, please let me know.
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From: Dipayaan Roy dipayanroy@linux.microsoft.com
[ Upstream commit 9448ccd853368582efa9db05db344f8bb9dffe0f ]
The hv_netvsc driver currently enables NAPI after opening the primary and subchannels. This ordering creates a race: if the Hyper-V host places data in the host -> guest ring buffer and signals the channel before napi_enable() has been called, the channel callback will run but napi_schedule_prep() will return false. As a result, the NAPI poller never gets scheduled, the data in the ring buffer is not consumed, and the receive queue may remain permanently stuck until another interrupt happens to arrive.
Fix this by enabling NAPI and registering it with the RX/TX queues before vmbus channel is opened. This guarantees that any early host signal after open will correctly trigger NAPI scheduling and the ring buffer will be drained.
Fixes: 76bb5db5c749d ("netvsc: fix use after free on module removal") Signed-off-by: Dipayaan Roy dipayanroy@linux.microsoft.com Link: https://patch.msgid.link/20250825115627.GA32189@linuxonhyperv3.guj3yctzbm1et... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/hyperv/netvsc.c | 17 ++++++++--------- drivers/net/hyperv/rndis_filter.c | 23 ++++++++++++++++------- 2 files changed, 24 insertions(+), 16 deletions(-)
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c index 87ac2a5f18091..5f14799b68c53 100644 --- a/drivers/net/hyperv/netvsc.c +++ b/drivers/net/hyperv/netvsc.c @@ -1811,6 +1811,11 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
/* Enable NAPI handler before init callbacks */ netif_napi_add(ndev, &net_device->chan_table[0].napi, netvsc_poll); + napi_enable(&net_device->chan_table[0].napi); + netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_RX, + &net_device->chan_table[0].napi); + netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_TX, + &net_device->chan_table[0].napi);
/* Open the channel */ device->channel->next_request_id_callback = vmbus_next_request_id; @@ -1830,12 +1835,6 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device, /* Channel is opened */ netdev_dbg(ndev, "hv_netvsc channel opened successfully\n");
- napi_enable(&net_device->chan_table[0].napi); - netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_RX, - &net_device->chan_table[0].napi); - netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_TX, - &net_device->chan_table[0].napi); - /* Connect with the NetVsp */ ret = netvsc_connect_vsp(device, net_device, device_info); if (ret != 0) { @@ -1853,14 +1852,14 @@ struct netvsc_device *netvsc_device_add(struct hv_device *device,
close: RCU_INIT_POINTER(net_device_ctx->nvdev, NULL); - netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_TX, NULL); - netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_RX, NULL); - napi_disable(&net_device->chan_table[0].napi);
/* Now, we can close the channel safely */ vmbus_close(device->channel);
cleanup: + netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_TX, NULL); + netif_queue_set_napi(ndev, 0, NETDEV_QUEUE_TYPE_RX, NULL); + napi_disable(&net_device->chan_table[0].napi); netif_napi_del(&net_device->chan_table[0].napi);
cleanup2: diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c index 9b8769a8b77a1..9a92552ee35c2 100644 --- a/drivers/net/hyperv/rndis_filter.c +++ b/drivers/net/hyperv/rndis_filter.c @@ -1252,17 +1252,26 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc) new_sc->rqstor_size = netvsc_rqstor_size(netvsc_ring_bytes); new_sc->max_pkt_size = NETVSC_MAX_PKT_SIZE;
+ /* Enable napi before opening the vmbus channel to avoid races + * as the host placing data on the host->guest ring may be left + * out if napi was not enabled. + */ + napi_enable(&nvchan->napi); + netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_RX, + &nvchan->napi); + netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_TX, + &nvchan->napi); + ret = vmbus_open(new_sc, netvsc_ring_bytes, netvsc_ring_bytes, NULL, 0, netvsc_channel_cb, nvchan); - if (ret == 0) { - napi_enable(&nvchan->napi); - netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_RX, - &nvchan->napi); - netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_TX, - &nvchan->napi); - } else { + if (ret != 0) { netdev_notice(ndev, "sub channel open failed: %d\n", ret); + netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_TX, + NULL); + netif_queue_set_napi(ndev, chn_index, NETDEV_QUEUE_TYPE_RX, + NULL); + napi_disable(&nvchan->napi); }
if (atomic_inc_return(&nvscdev->open_chn) == nvscdev->num_chn)