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 <[email protected]> Signed-off-by: Andrea Parri (Microsoft) <[email protected]> --- 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
