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    Subject[RFC PATCH 2/4] PCI: hv: Use vmbus_requestor to generate transaction IDs for VMbus hardening
    Date
    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 <mikelley@microsoft.com>
    Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
    ---
    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
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