The hv_message object is in memory shared with the host. To prevent
an erroneous or a malicious host from 'corrupting' such object, copy
the object into private memory.
Suggested-by: Juan Vazquez <juvazq@xxxxxxxxxxxxx>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
---
drivers/hv/vmbus_drv.c | 26 +++++++++++++++-----------
1 file changed, 15 insertions(+), 11 deletions(-)
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 0e39f1d6182e9..796202aa7f9b4 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1054,14 +1054,24 @@ 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;
- __u8 payload_size = msg->header.payload_size;
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;
+
+ /*
+ * The hv_message object is in memory shared with the host. Prevent an
+ * erroneous or malicious host from 'corrupting' such object by copying
+ * the object to private memory.
+ */
+ memcpy(&msg_copy, msg, sizeof(struct hv_message));
+
+ payload_size = msg_copy.header.payload_size;
+ message_type = msg_copy.header.message_type;
/*
* 'enum vmbus_channel_message_type' is supposed to always be 'u32' as
@@ -1074,13 +1084,7 @@ void vmbus_on_msg_dpc(unsigned long data)
/* no msg */
return;
- /*
- * The hv_message object is in memory shared with the host. The host
- * could erroneously or maliciously modify such object. Make sure to
- * validate its fields and avoid double fetches whenever feasible.
- */
-
- 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);
@@ -1111,7 +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_copy.header) + payload_size);
/*
* The host can generate a rescind message while we
--
2.25.1
