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Subject[PATCH v2 1/2] PCI: hv: Add validation for untrusted Hyper-V values
Date
For additional robustness in the face of Hyper-V errors or malicious
behavior, validate all values that originate from packets that Hyper-V
has sent to the guest in the host-to-guest ring buffer. Ensure that
invalid values cannot cause data being copied out of the bounds of the
source buffer in hv_pci_onchannelcallback().

While at it, remove a redundant validation in hv_pci_generic_compl():
hv_pci_onchannelcallback() already ensures that all processed incoming
packets are "at least as large as [in fact larger than] a response".

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
---
drivers/pci/controller/pci-hyperv.c | 33 +++++++++++++++++++++--------
1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index e439b810f974b..a06e2cf946580 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -981,11 +981,7 @@ static void hv_pci_generic_compl(void *context, struct pci_response *resp,
{
struct hv_pci_compl *comp_pkt = context;

- if (resp_packet_size >= offsetofend(struct pci_response, status))
- comp_pkt->completion_status = resp->status;
- else
- comp_pkt->completion_status = -1;
-
+ comp_pkt->completion_status = resp->status;
complete(&comp_pkt->host_event);
}

@@ -1606,8 +1602,13 @@ static void hv_pci_compose_compl(void *context, struct pci_response *resp,
struct pci_create_int_response *int_resp =
(struct pci_create_int_response *)resp;

+ if (resp_packet_size < sizeof(*int_resp)) {
+ comp_pkt->comp_pkt.completion_status = -1;
+ goto out;
+ }
comp_pkt->comp_pkt.completion_status = resp->status;
comp_pkt->int_desc = int_resp->int_desc;
+out:
complete(&comp_pkt->comp_pkt.host_event);
}

@@ -2291,12 +2292,14 @@ static void q_resource_requirements(void *context, struct pci_response *resp,
struct q_res_req_compl *completion = context;
struct pci_q_res_req_response *q_res_req =
(struct pci_q_res_req_response *)resp;
+ s32 status;
int i;

- if (resp->status < 0) {
+ status = (resp_packet_size < sizeof(*q_res_req)) ? -1 : resp->status;
+ if (status < 0) {
dev_err(&completion->hpdev->hbus->hdev->device,
"query resource requirements failed: %x\n",
- resp->status);
+ status);
} else {
for (i = 0; i < PCI_STD_NUM_BARS; i++) {
completion->hpdev->probed_bar[i] =
@@ -2848,7 +2851,8 @@ static void hv_pci_onchannelcallback(void *context)
case PCI_BUS_RELATIONS:

bus_rel = (struct pci_bus_relations *)buffer;
- if (bytes_recvd <
+ if (bytes_recvd < sizeof(*bus_rel) ||
+ bytes_recvd <
struct_size(bus_rel, func,
bus_rel->device_count)) {
dev_err(&hbus->hdev->device,
@@ -2862,7 +2866,8 @@ static void hv_pci_onchannelcallback(void *context)
case PCI_BUS_RELATIONS2:

bus_rel2 = (struct pci_bus_relations2 *)buffer;
- if (bytes_recvd <
+ if (bytes_recvd < sizeof(*bus_rel2) ||
+ bytes_recvd <
struct_size(bus_rel2, func,
bus_rel2->device_count)) {
dev_err(&hbus->hdev->device,
@@ -2876,6 +2881,11 @@ static void hv_pci_onchannelcallback(void *context)
case PCI_EJECT:

dev_message = (struct pci_dev_incoming *)buffer;
+ if (bytes_recvd < sizeof(*dev_message)) {
+ dev_err(&hbus->hdev->device,
+ "eject message too small\n");
+ break;
+ }
hpdev = get_pcichild_wslot(hbus,
dev_message->wslot.slot);
if (hpdev) {
@@ -2887,6 +2897,11 @@ static void hv_pci_onchannelcallback(void *context)
case PCI_INVALIDATE_BLOCK:

inval = (struct pci_dev_inval_block *)buffer;
+ if (bytes_recvd < sizeof(*inval)) {
+ dev_err(&hbus->hdev->device,
+ "invalidate message too small\n");
+ break;
+ }
hpdev = get_pcichild_wslot(hbus,
inval->wslot.slot);
if (hpdev) {
--
2.25.1
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