Currently, pointers to guest memory are passed to Hyper-V as transaction
IDs in hv_pci. In the face of errors or malicious behavior in Hyper-V,
hv_pci should not expose or trust the transaction IDs returned by
Hyper-V to be valid guest memory addresses. Instead, use small integers
generated by vmbus_requestor as request (transaction) IDs.
Suggested-by: Michael Kelley <[email protected]>
Signed-off-by: Andrea Parri (Microsoft) <[email protected]>
---
drivers/pci/controller/pci-hyperv.c | 30 +++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index ae0bc2fee4ca8..9f963a46b8298 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -91,6 +91,9 @@ static enum pci_protocol_version_t pci_protocol_versions[] = {
/* space for 32bit serial number as string */
#define SLOT_NAME_SIZE 11
+/* Size of requestor for VMbus */
+#define HV_PCI_RQSTOR_SIZE 64
+
/*
* Message Types
*/
@@ -1407,7 +1410,7 @@ static void hv_int_desc_free(struct hv_pci_dev *hpdev,
int_pkt->wslot.slot = hpdev->desc.win_slot.slot;
int_pkt->int_desc = *int_desc;
vmbus_sendpacket(hpdev->hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
- (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND, 0);
+ 0, VM_PKT_DATA_INBAND, 0);
kfree(int_desc);
}
@@ -2649,7 +2652,7 @@ static void hv_eject_device_work(struct work_struct *work)
ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
ejct_pkt->wslot.slot = hpdev->desc.win_slot.slot;
vmbus_sendpacket(hbus->hdev->channel, ejct_pkt,
- sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
+ sizeof(*ejct_pkt), 0,
VM_PKT_DATA_INBAND, 0);
/* For the get_pcichild() in hv_pci_eject_device() */
@@ -2696,8 +2699,9 @@ static void hv_pci_onchannelcallback(void *context)
const int packet_size = 0x100;
int ret;
struct hv_pcibus_device *hbus = context;
+ struct vmbus_channel *chan = hbus->hdev->channel;
u32 bytes_recvd;
- u64 req_id;
+ u64 req_id, req_addr;
struct vmpacket_descriptor *desc;
unsigned char *buffer;
int bufferlen = packet_size;
@@ -2743,11 +2747,13 @@ static void hv_pci_onchannelcallback(void *context)
switch (desc->type) {
case VM_PKT_COMP:
- /*
- * The host is trusted, and thus it's safe to interpret
- * this transaction ID as a pointer.
- */
- comp_packet = (struct pci_packet *)req_id;
+ req_addr = chan->request_addr_callback(chan, req_id);
+ if (req_addr == VMBUS_RQST_ERROR) {
+ dev_warn_ratelimited(&hbus->hdev->device,
+ "Invalid request ID\n");
+ break;
+ }
+ comp_packet = (struct pci_packet *)req_addr;
response = (struct pci_response *)buffer;
comp_packet->completion_func(comp_packet->compl_ctxt,
response,
@@ -3419,6 +3425,10 @@ static int hv_pci_probe(struct hv_device *hdev,
goto free_dom;
}
+ hdev->channel->next_request_id_callback = vmbus_next_request_id;
+ hdev->channel->request_addr_callback = vmbus_request_addr;
+ hdev->channel->rqstor_size = HV_PCI_RQSTOR_SIZE;
+
ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
hv_pci_onchannelcallback, hbus);
if (ret)
@@ -3749,6 +3759,10 @@ static int hv_pci_resume(struct hv_device *hdev)
hbus->state = hv_pcibus_init;
+ hdev->channel->next_request_id_callback = vmbus_next_request_id;
+ hdev->channel->request_addr_callback = vmbus_request_addr;
+ hdev->channel->rqstor_size = HV_PCI_RQSTOR_SIZE;
+
ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
hv_pci_onchannelcallback, hbus);
if (ret)
--
2.25.1
From: Andrea Parri (Microsoft) <[email protected]> Sent: Monday, March 28, 2022 7:43 AM
>
> Currently, pointers to guest memory are passed to Hyper-V as transaction
> IDs in hv_pci. In the face of errors or malicious behavior in Hyper-V,
> hv_pci should not expose or trust the transaction IDs returned by
> Hyper-V to be valid guest memory addresses. Instead, use small integers
> generated by vmbus_requestor as request (transaction) IDs.
>
> Suggested-by: Michael Kelley <[email protected]>
> Signed-off-by: Andrea Parri (Microsoft) <[email protected]>
> ---
> drivers/pci/controller/pci-hyperv.c | 30 +++++++++++++++++++++--------
> 1 file changed, 22 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index ae0bc2fee4ca8..9f963a46b8298 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -91,6 +91,9 @@ static enum pci_protocol_version_t pci_protocol_versions[] = {
> /* space for 32bit serial number as string */
> #define SLOT_NAME_SIZE 11
>
> +/* Size of requestor for VMbus */
> +#define HV_PCI_RQSTOR_SIZE 64
Might include a comment about how this value was derived. I *think*
it is an arbitrary value based on the assumption that having more than
one request outstanding is rare, and so 64 should be extremely generous
in ensuring that we don't ever run out.
> +
> /*
> * Message Types
> */
> @@ -1407,7 +1410,7 @@ static void hv_int_desc_free(struct hv_pci_dev *hpdev,
> int_pkt->wslot.slot = hpdev->desc.win_slot.slot;
> int_pkt->int_desc = *int_desc;
> vmbus_sendpacket(hpdev->hbus->hdev->channel, int_pkt, sizeof(*int_pkt),
> - (unsigned long)&ctxt.pkt, VM_PKT_DATA_INBAND, 0);
> + 0, VM_PKT_DATA_INBAND, 0);
> kfree(int_desc);
> }
>
> @@ -2649,7 +2652,7 @@ static void hv_eject_device_work(struct work_struct *work)
> ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
> ejct_pkt->wslot.slot = hpdev->desc.win_slot.slot;
> vmbus_sendpacket(hbus->hdev->channel, ejct_pkt,
> - sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
> + sizeof(*ejct_pkt), 0,
> VM_PKT_DATA_INBAND, 0);
>
> /* For the get_pcichild() in hv_pci_eject_device() */
> @@ -2696,8 +2699,9 @@ static void hv_pci_onchannelcallback(void *context)
> const int packet_size = 0x100;
> int ret;
> struct hv_pcibus_device *hbus = context;
> + struct vmbus_channel *chan = hbus->hdev->channel;
Having gotten the channel as a local variable, could also use the local as
the first argument to vmbus_recvpacket_raw().
> u32 bytes_recvd;
> - u64 req_id;
> + u64 req_id, req_addr;
> struct vmpacket_descriptor *desc;
> unsigned char *buffer;
> int bufferlen = packet_size;
> @@ -2743,11 +2747,13 @@ static void hv_pci_onchannelcallback(void *context)
> switch (desc->type) {
> case VM_PKT_COMP:
>
> - /*
> - * The host is trusted, and thus it's safe to interpret
> - * this transaction ID as a pointer.
> - */
> - comp_packet = (struct pci_packet *)req_id;
> + req_addr = chan->request_addr_callback(chan, req_id);
> + if (req_addr == VMBUS_RQST_ERROR) {
> + dev_warn_ratelimited(&hbus->hdev->device,
> + "Invalid request ID\n");
Could you include the req_id value in the error message that is output? I
was recently debugging a problem in the storvsc driver where having that
value would have been handy.
> + break;
> + }
> + comp_packet = (struct pci_packet *)req_addr;
> response = (struct pci_response *)buffer;
> comp_packet->completion_func(comp_packet->compl_ctxt,
> response,
> @@ -3419,6 +3425,10 @@ static int hv_pci_probe(struct hv_device *hdev,
> goto free_dom;
> }
>
> + hdev->channel->next_request_id_callback = vmbus_next_request_id;
> + hdev->channel->request_addr_callback = vmbus_request_addr;
> + hdev->channel->rqstor_size = HV_PCI_RQSTOR_SIZE;
> +
> ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
> hv_pci_onchannelcallback, hbus);
> if (ret)
> @@ -3749,6 +3759,10 @@ static int hv_pci_resume(struct hv_device *hdev)
>
> hbus->state = hv_pcibus_init;
>
> + hdev->channel->next_request_id_callback = vmbus_next_request_id;
> + hdev->channel->request_addr_callback = vmbus_request_addr;
> + hdev->channel->rqstor_size = HV_PCI_RQSTOR_SIZE;
> +
> ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
> hv_pci_onchannelcallback, hbus);
> if (ret)
> --
> 2.25.1
> > @@ -91,6 +91,9 @@ static enum pci_protocol_version_t pci_protocol_versions[] = {
> > /* space for 32bit serial number as string */
> > #define SLOT_NAME_SIZE 11
> >
> > +/* Size of requestor for VMbus */
> > +#define HV_PCI_RQSTOR_SIZE 64
>
> Might include a comment about how this value was derived. I *think*
> it is an arbitrary value based on the assumption that having more than
> one request outstanding is rare, and so 64 should be extremely generous
> in ensuring that we don't ever run out.
Right, I've added a comment to that effect.
> > @@ -2696,8 +2699,9 @@ static void hv_pci_onchannelcallback(void *context)
> > const int packet_size = 0x100;
> > int ret;
> > struct hv_pcibus_device *hbus = context;
> > + struct vmbus_channel *chan = hbus->hdev->channel;
>
> Having gotten the channel as a local variable, could also use the local as
> the first argument to vmbus_recvpacket_raw().
Applied.
> > @@ -2743,11 +2747,13 @@ static void hv_pci_onchannelcallback(void *context)
> > switch (desc->type) {
> > case VM_PKT_COMP:
> >
> > - /*
> > - * The host is trusted, and thus it's safe to interpret
> > - * this transaction ID as a pointer.
> > - */
> > - comp_packet = (struct pci_packet *)req_id;
> > + req_addr = chan->request_addr_callback(chan, req_id);
> > + if (req_addr == VMBUS_RQST_ERROR) {
> > + dev_warn_ratelimited(&hbus->hdev->device,
> > + "Invalid request ID\n");
>
> Could you include the req_id value in the error message that is output? I
> was recently debugging a problem in the storvsc driver where having that
> value would have been handy.
Sure.
Thanks,
Andrea