[PATCH v4 net] net: hv_netvsc: fix netvsc_send_completion to avoid multiple message length checks

Sonia Sharma
2023-09-07T19:57:14Z

From: Sonia Sharma <sonia.sharma@linux.microsoft.com>

The switch statement in netvsc_send_completion() is incorrectly validating
the length of incoming network packets by falling through to the next case.
Avoid the fallthrough. Instead break after a case match and then process
the complete() call.
The current code has not caused any known failures. But nonetheless, the
code should be corrected as a different ordering of the switch cases might
cause a length check to fail when it should not.

Fixes: 44144185951a0f ("hv_netvsc: Add validation for untrusted Hyper-V values")
Signed-off-by: Sonia Sharma <sonia.sharma@linux.microsoft.com>

---
Changes in v3:
* added return statement in default case as pointed by Michael Kelley.
Changes in v4:
* added fixes tag
* modified commit message to explain the issue fixed by patch.
---
drivers/net/hyperv/netvsc.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 82e9796c8f5e..0f7e4d377776 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -851,7 +851,7 @@ static void netvsc_send_completion(struct net_device *ndev,
msglen);
return;
}
- fallthrough;
+ break;

case NVSP_MSG1_TYPE_SEND_RECV_BUF_COMPLETE:
if (msglen < sizeof(struct nvsp_message_header) +
@@ -860,7 +860,7 @@ static void netvsc_send_completion(struct net_device *ndev,
msglen);
return;
}
- fallthrough;
+ break;

case NVSP_MSG1_TYPE_SEND_SEND_BUF_COMPLETE:
if (msglen < sizeof(struct nvsp_message_header) +
@@ -869,7 +869,7 @@ static void netvsc_send_completion(struct net_device *ndev,
msglen);
return;
}
- fallthrough;
+ break;

case NVSP_MSG5_TYPE_SUBCHANNEL:
if (msglen < sizeof(struct nvsp_message_header) +
@@ -878,10 +878,6 @@ static void netvsc_send_completion(struct net_device *ndev,
msglen);
return;
}
- /* Copy the response back */
- memcpy(&net_device->channel_init_pkt, nvsp_packet,
- sizeof(struct nvsp_message));
- complete(&net_device->channel_init_wait);
break;

case NVSP_MSG1_TYPE_SEND_RNDIS_PKT_COMPLETE:
@@ -904,13 +900,19 @@ static void netvsc_send_completion(struct net_device *ndev,

netvsc_send_tx_complete(ndev, net_device, incoming_channel,
desc, budget);
- break;
+ return;

default:
netdev_err(ndev,
"Unknown send completion type %d received!!\n",
nvsp_packet->hdr.msg_type);
+ return;
}
+
+ /* Copy the response back */
+ memcpy(&net_device->channel_init_pkt, nvsp_packet,
+ sizeof(struct nvsp_message));
+ complete(&net_device->channel_init_wait);
}

static u32 netvsc_get_next_send_section(struct netvsc_device *net_device)
--
2.25.1