Since the message is in memory shared with the host, an erroneous or a
malicious Hyper-V could 'corrupt' the message while vmbus_on_msg_dpc()
or individual message handlers are executing. To prevent it, copy the
message into private memory.
Reported-by: Juan Vazquez <juvazq@xxxxxxxxxxxxx>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
---
Changes since v2:
- Revisit commit message and inline comment
drivers/hv/vmbus_drv.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 44bcf9ccdaf5f..b1c5a89d75f9d 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1054,14 +1054,14 @@ void vmbus_on_msg_dpc(unsigned long data)
{
struct hv_per_cpu_context *hv_cpu = (void *)data;
void *page_addr = hv_cpu->synic_message_page;
- struct hv_message *msg = (struct hv_message *)page_addr +
+ struct hv_message msg_copy, *msg = (struct hv_message *)page_addr +
VMBUS_MESSAGE_SINT;
struct vmbus_channel_message_header *hdr;
enum vmbus_channel_message_type msgtype;
const struct vmbus_channel_message_table_entry *entry;
struct onmessage_work_context *ctx;
- u32 message_type = msg->header.message_type;
__u8 payload_size;
+ u32 message_type;
/*
* 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
@@ -1070,11 +1070,20 @@ void vmbus_on_msg_dpc(unsigned long data)
*/
BUILD_BUG_ON(sizeof(enum vmbus_channel_message_type) != sizeof(u32));
+ /*
+ * Since the message is in memory shared with the host, an erroneous or
+ * malicious Hyper-V could modify the message while vmbus_on_msg_dpc()
+ * or individual message handlers are executing; to prevent this, copy
+ * the message into private memory.
+ */
+ memcpy(&msg_copy, msg, sizeof(struct hv_message));
+
+ message_type = msg_copy.header.message_type;
if (message_type == HVMSG_NONE)
/* no msg */
return;
- hdr = (struct vmbus_channel_message_header *)msg->u.payload;
+ hdr = (struct vmbus_channel_message_header *)msg_copy.u.payload;
msgtype = hdr->msgtype;
trace_vmbus_on_msg_dpc(hdr);
@@ -1084,7 +1093,7 @@ void vmbus_on_msg_dpc(unsigned long data)
goto msg_handled;
}
- payload_size = msg->header.payload_size;
+ payload_size = msg_copy.header.payload_size;
if (payload_size > HV_MESSAGE_PAYLOAD_BYTE_COUNT) {
WARN_ONCE(1, "payload size is too large (%d)\n", payload_size);
goto msg_handled;
@@ -1106,7 +1115,7 @@ void vmbus_on_msg_dpc(unsigned long data)
return;
INIT_WORK(&ctx->work, vmbus_onmessage_work);
- memcpy(&ctx->msg, msg, sizeof(msg->header) + payload_size);
+ memcpy(&ctx->msg, &msg_copy, sizeof(msg->header) + payload_size);
/*
* The host can generate a rescind message while we
--
2.25.1
