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Subject[PATCH v7 2/3] scsi: storvsc: Use vmbus_requestor to generate transaction IDs for VMBus hardening
Date
From: Andres Beltran <lkmlabelt@gmail.com>

Currently, pointers to guest memory are passed to Hyper-V as
transaction IDs in storvsc. In the face of errors or malicious
behavior in Hyper-V, storvsc 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 requests
(transaction) IDs.

Signed-off-by: Andres Beltran <lkmlabelt@gmail.com>
Co-developed-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
---
Changes in v7:
- Move the allocation of the request ID after the data has been
copied into the ring buffer (cf. 1/3).
Changes in v2:
- Add casts to unsigned long to fix warnings on 32bit.

drivers/scsi/storvsc_drv.c | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index 8f5f5dc863a4a..0b9090d031fc0 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -399,6 +399,7 @@ static int storvsc_timeout = 180;
static struct scsi_transport_template *fc_transport_template;
#endif

+static struct scsi_host_template scsi_driver;
static void storvsc_on_channel_callback(void *context);

#define STORVSC_MAX_LUNS_PER_TARGET 255
@@ -698,6 +699,12 @@ static void handle_sc_creation(struct vmbus_channel *new_sc)

memset(&props, 0, sizeof(struct vmstorage_channel_properties));

+ /*
+ * The size of vmbus_requestor is an upper bound on the number of requests
+ * that can be in-progress at any one time across all channels.
+ */
+ new_sc->rqstor_size = scsi_driver.can_queue;
+
ret = vmbus_open(new_sc,
storvsc_ringbuffer_size,
storvsc_ringbuffer_size,
@@ -1242,9 +1249,17 @@ static void storvsc_on_channel_callback(void *context)
foreach_vmbus_pkt(desc, channel) {
void *packet = hv_pkt_data(desc);
struct storvsc_cmd_request *request;
+ u64 cmd_rqst;
+
+ cmd_rqst = vmbus_request_addr(&channel->requestor,
+ desc->trans_id);
+ if (cmd_rqst == VMBUS_RQST_ERROR) {
+ dev_err(&device->device,
+ "Incorrect transaction id\n");
+ continue;
+ }

- request = (struct storvsc_cmd_request *)
- ((unsigned long)desc->trans_id);
+ request = (struct storvsc_cmd_request *)(unsigned long)cmd_rqst;

if (request == &stor_device->init_request ||
request == &stor_device->reset_request) {
@@ -1265,6 +1280,12 @@ static int storvsc_connect_to_vsp(struct hv_device *device, u32 ring_size,

memset(&props, 0, sizeof(struct vmstorage_channel_properties));

+ /*
+ * The size of vmbus_requestor is an upper bound on the number of requests
+ * that can be in-progress at any one time across all channels.
+ */
+ device->channel->rqstor_size = scsi_driver.can_queue;
+
ret = vmbus_open(device->channel,
ring_size,
ring_size,
@@ -1572,7 +1593,6 @@ static int storvsc_host_reset_handler(struct scsi_cmnd *scmnd)
struct vstor_packet *vstor_packet;
int ret, t;

-
stor_device = get_out_stor_device(device);
if (!stor_device)
return FAILED;
--
2.25.1
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