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![Michael Kelley](/assets/img/avatar_default.png)
The VSS driver allocates a VMbus receive buffer significantly larger than sizeof(hv_vss_msg), with no explanation. To help prevent future mistakes, add a #define and comment about why this is done. No functional change. Signed-off-by: Michael Kelley <mikelley@microsoft.com> Link: https://lore.kernel.org/r/1644423070-75125-1-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu <wei.liu@kernel.org>
458 lines
12 KiB
C
458 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* An implementation of host initiated guest snapshot.
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*
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* Copyright (C) 2013, Microsoft, Inc.
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* Author : K. Y. Srinivasan <kys@microsoft.com>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/net.h>
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#include <linux/nls.h>
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#include <linux/connector.h>
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#include <linux/workqueue.h>
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#include <linux/hyperv.h>
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#include <asm/hyperv-tlfs.h>
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#include "hyperv_vmbus.h"
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#include "hv_utils_transport.h"
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#define VSS_MAJOR 5
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#define VSS_MINOR 0
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#define VSS_VERSION (VSS_MAJOR << 16 | VSS_MINOR)
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#define VSS_VER_COUNT 1
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static const int vss_versions[] = {
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VSS_VERSION
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};
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#define FW_VER_COUNT 1
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static const int fw_versions[] = {
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UTIL_FW_VERSION
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};
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/* See comment with struct hv_vss_msg regarding the max VMbus packet size */
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#define VSS_MAX_PKT_SIZE (HV_HYP_PAGE_SIZE * 2)
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/*
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* Timeout values are based on expecations from host
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*/
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#define VSS_FREEZE_TIMEOUT (15 * 60)
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/*
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* Global state maintained for transaction that is being processed. For a class
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* of integration services, including the "VSS service", the specified protocol
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* is a "request/response" protocol which means that there can only be single
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* outstanding transaction from the host at any given point in time. We use
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* this to simplify memory management in this driver - we cache and process
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* only one message at a time.
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*
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* While the request/response protocol is guaranteed by the host, we further
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* ensure this by serializing packet processing in this driver - we do not
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* read additional packets from the VMBUs until the current packet is fully
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* handled.
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*/
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static struct {
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int state; /* hvutil_device_state */
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int recv_len; /* number of bytes received. */
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struct vmbus_channel *recv_channel; /* chn we got the request */
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u64 recv_req_id; /* request ID. */
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struct hv_vss_msg *msg; /* current message */
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} vss_transaction;
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static void vss_respond_to_host(int error);
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/*
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* This state maintains the version number registered by the daemon.
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*/
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static int dm_reg_value;
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static const char vss_devname[] = "vmbus/hv_vss";
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static __u8 *recv_buffer;
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static struct hvutil_transport *hvt;
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static void vss_timeout_func(struct work_struct *dummy);
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static void vss_handle_request(struct work_struct *dummy);
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static DECLARE_DELAYED_WORK(vss_timeout_work, vss_timeout_func);
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static DECLARE_WORK(vss_handle_request_work, vss_handle_request);
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static void vss_poll_wrapper(void *channel)
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{
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/* Transaction is finished, reset the state here to avoid races. */
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vss_transaction.state = HVUTIL_READY;
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tasklet_schedule(&((struct vmbus_channel *)channel)->callback_event);
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}
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/*
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* Callback when data is received from user mode.
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*/
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static void vss_timeout_func(struct work_struct *dummy)
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{
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/*
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* Timeout waiting for userspace component to reply happened.
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*/
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pr_warn("VSS: timeout waiting for daemon to reply\n");
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vss_respond_to_host(HV_E_FAIL);
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hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
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}
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static void vss_register_done(void)
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{
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hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
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pr_debug("VSS: userspace daemon registered\n");
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}
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static int vss_handle_handshake(struct hv_vss_msg *vss_msg)
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{
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u32 our_ver = VSS_OP_REGISTER1;
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switch (vss_msg->vss_hdr.operation) {
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case VSS_OP_REGISTER:
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/* Daemon doesn't expect us to reply */
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dm_reg_value = VSS_OP_REGISTER;
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break;
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case VSS_OP_REGISTER1:
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/* Daemon expects us to reply with our own version */
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if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver),
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vss_register_done))
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return -EFAULT;
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dm_reg_value = VSS_OP_REGISTER1;
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break;
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default:
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return -EINVAL;
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}
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pr_info("VSS: userspace daemon ver. %d connected\n", dm_reg_value);
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return 0;
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}
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static int vss_on_msg(void *msg, int len)
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{
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struct hv_vss_msg *vss_msg = (struct hv_vss_msg *)msg;
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if (len != sizeof(*vss_msg)) {
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pr_debug("VSS: Message size does not match length\n");
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return -EINVAL;
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}
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if (vss_msg->vss_hdr.operation == VSS_OP_REGISTER ||
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vss_msg->vss_hdr.operation == VSS_OP_REGISTER1) {
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/*
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* Don't process registration messages if we're in the middle
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* of a transaction processing.
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*/
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if (vss_transaction.state > HVUTIL_READY) {
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pr_debug("VSS: Got unexpected registration request\n");
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return -EINVAL;
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}
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return vss_handle_handshake(vss_msg);
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} else if (vss_transaction.state == HVUTIL_USERSPACE_REQ) {
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vss_transaction.state = HVUTIL_USERSPACE_RECV;
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if (vss_msg->vss_hdr.operation == VSS_OP_HOT_BACKUP)
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vss_transaction.msg->vss_cf.flags =
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VSS_HBU_NO_AUTO_RECOVERY;
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if (cancel_delayed_work_sync(&vss_timeout_work)) {
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vss_respond_to_host(vss_msg->error);
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/* Transaction is finished, reset the state. */
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hv_poll_channel(vss_transaction.recv_channel,
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vss_poll_wrapper);
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}
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} else {
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/* This is a spurious call! */
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pr_debug("VSS: Transaction not active\n");
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return -EINVAL;
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}
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return 0;
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}
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static void vss_send_op(void)
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{
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int op = vss_transaction.msg->vss_hdr.operation;
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int rc;
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struct hv_vss_msg *vss_msg;
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/* The transaction state is wrong. */
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if (vss_transaction.state != HVUTIL_HOSTMSG_RECEIVED) {
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pr_debug("VSS: Unexpected attempt to send to daemon\n");
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return;
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}
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vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
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if (!vss_msg)
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return;
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vss_msg->vss_hdr.operation = op;
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vss_transaction.state = HVUTIL_USERSPACE_REQ;
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schedule_delayed_work(&vss_timeout_work, op == VSS_OP_FREEZE ?
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VSS_FREEZE_TIMEOUT * HZ : HV_UTIL_TIMEOUT * HZ);
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rc = hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
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if (rc) {
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pr_warn("VSS: failed to communicate to the daemon: %d\n", rc);
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if (cancel_delayed_work_sync(&vss_timeout_work)) {
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vss_respond_to_host(HV_E_FAIL);
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vss_transaction.state = HVUTIL_READY;
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}
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}
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kfree(vss_msg);
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}
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static void vss_handle_request(struct work_struct *dummy)
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{
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switch (vss_transaction.msg->vss_hdr.operation) {
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/*
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* Initiate a "freeze/thaw" operation in the guest.
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* We respond to the host once the operation is complete.
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*
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* We send the message to the user space daemon and the operation is
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* performed in the daemon.
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*/
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case VSS_OP_THAW:
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case VSS_OP_FREEZE:
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case VSS_OP_HOT_BACKUP:
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if (vss_transaction.state < HVUTIL_READY) {
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/* Userspace is not registered yet */
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pr_debug("VSS: Not ready for request.\n");
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vss_respond_to_host(HV_E_FAIL);
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return;
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}
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pr_debug("VSS: Received request for op code: %d\n",
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vss_transaction.msg->vss_hdr.operation);
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vss_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
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vss_send_op();
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return;
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case VSS_OP_GET_DM_INFO:
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vss_transaction.msg->dm_info.flags = 0;
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break;
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default:
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break;
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}
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vss_respond_to_host(0);
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hv_poll_channel(vss_transaction.recv_channel, vss_poll_wrapper);
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}
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/*
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* Send a response back to the host.
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*/
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static void
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vss_respond_to_host(int error)
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{
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struct icmsg_hdr *icmsghdrp;
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u32 buf_len;
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struct vmbus_channel *channel;
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u64 req_id;
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/*
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* Copy the global state for completing the transaction. Note that
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* only one transaction can be active at a time.
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*/
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buf_len = vss_transaction.recv_len;
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channel = vss_transaction.recv_channel;
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req_id = vss_transaction.recv_req_id;
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icmsghdrp = (struct icmsg_hdr *)
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&recv_buffer[sizeof(struct vmbuspipe_hdr)];
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if (channel->onchannel_callback == NULL)
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/*
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* We have raced with util driver being unloaded;
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* silently return.
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*/
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return;
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icmsghdrp->status = error;
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icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
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vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
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VM_PKT_DATA_INBAND, 0);
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}
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/*
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* This callback is invoked when we get a VSS message from the host.
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* The host ensures that only one VSS transaction can be active at a time.
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*/
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void hv_vss_onchannelcallback(void *context)
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{
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struct vmbus_channel *channel = context;
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u32 recvlen;
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u64 requestid;
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struct hv_vss_msg *vss_msg;
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int vss_srv_version;
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struct icmsg_hdr *icmsghdrp;
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if (vss_transaction.state > HVUTIL_READY)
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return;
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if (vmbus_recvpacket(channel, recv_buffer, VSS_MAX_PKT_SIZE, &recvlen, &requestid)) {
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pr_err_ratelimited("VSS request received. Could not read into recv buf\n");
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return;
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}
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if (!recvlen)
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return;
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/* Ensure recvlen is big enough to read header data */
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if (recvlen < ICMSG_HDR) {
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pr_err_ratelimited("VSS request received. Packet length too small: %d\n",
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recvlen);
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return;
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}
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icmsghdrp = (struct icmsg_hdr *)&recv_buffer[sizeof(struct vmbuspipe_hdr)];
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if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
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if (vmbus_prep_negotiate_resp(icmsghdrp,
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recv_buffer, recvlen,
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fw_versions, FW_VER_COUNT,
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vss_versions, VSS_VER_COUNT,
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NULL, &vss_srv_version)) {
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pr_info("VSS IC version %d.%d\n",
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vss_srv_version >> 16,
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vss_srv_version & 0xFFFF);
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}
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} else if (icmsghdrp->icmsgtype == ICMSGTYPE_VSS) {
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/* Ensure recvlen is big enough to contain hv_vss_msg */
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if (recvlen < ICMSG_HDR + sizeof(struct hv_vss_msg)) {
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pr_err_ratelimited("Invalid VSS msg. Packet length too small: %u\n",
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recvlen);
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return;
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}
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vss_msg = (struct hv_vss_msg *)&recv_buffer[ICMSG_HDR];
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/*
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* Stash away this global state for completing the
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* transaction; note transactions are serialized.
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*/
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vss_transaction.recv_len = recvlen;
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vss_transaction.recv_req_id = requestid;
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vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
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schedule_work(&vss_handle_request_work);
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return;
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} else {
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pr_err_ratelimited("VSS request received. Invalid msg type: %d\n",
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icmsghdrp->icmsgtype);
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return;
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}
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icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION |
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ICMSGHDRFLAG_RESPONSE;
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vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
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VM_PKT_DATA_INBAND, 0);
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}
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static void vss_on_reset(void)
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{
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if (cancel_delayed_work_sync(&vss_timeout_work))
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vss_respond_to_host(HV_E_FAIL);
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vss_transaction.state = HVUTIL_DEVICE_INIT;
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}
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int
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hv_vss_init(struct hv_util_service *srv)
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{
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if (vmbus_proto_version < VERSION_WIN8_1) {
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pr_warn("Integration service 'Backup (volume snapshot)'"
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" not supported on this host version.\n");
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return -ENOTSUPP;
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}
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recv_buffer = srv->recv_buffer;
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vss_transaction.recv_channel = srv->channel;
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vss_transaction.recv_channel->max_pkt_size = VSS_MAX_PKT_SIZE;
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/*
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* When this driver loads, the user level daemon that
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* processes the host requests may not yet be running.
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* Defer processing channel callbacks until the daemon
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* has registered.
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*/
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vss_transaction.state = HVUTIL_DEVICE_INIT;
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hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL,
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vss_on_msg, vss_on_reset);
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if (!hvt) {
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pr_warn("VSS: Failed to initialize transport\n");
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return -EFAULT;
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}
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return 0;
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}
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static void hv_vss_cancel_work(void)
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{
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cancel_delayed_work_sync(&vss_timeout_work);
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cancel_work_sync(&vss_handle_request_work);
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}
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int hv_vss_pre_suspend(void)
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{
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struct vmbus_channel *channel = vss_transaction.recv_channel;
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struct hv_vss_msg *vss_msg;
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/*
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* Fake a THAW message for the user space daemon in case the daemon
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* has frozen the file systems. It doesn't matter if there is already
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* a message pending to be delivered to the user space since we force
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* vss_transaction.state to be HVUTIL_READY, so the user space daemon's
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* write() will fail with EINVAL (see vss_on_msg()), and the daemon
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* will reset the device by closing and re-opening it.
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*/
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vss_msg = kzalloc(sizeof(*vss_msg), GFP_KERNEL);
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if (!vss_msg)
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return -ENOMEM;
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tasklet_disable(&channel->callback_event);
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vss_msg->vss_hdr.operation = VSS_OP_THAW;
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/* Cancel any possible pending work. */
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hv_vss_cancel_work();
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/* We don't care about the return value. */
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hvutil_transport_send(hvt, vss_msg, sizeof(*vss_msg), NULL);
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kfree(vss_msg);
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vss_transaction.state = HVUTIL_READY;
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/* tasklet_enable() will be called in hv_vss_pre_resume(). */
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return 0;
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}
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int hv_vss_pre_resume(void)
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{
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struct vmbus_channel *channel = vss_transaction.recv_channel;
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tasklet_enable(&channel->callback_event);
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return 0;
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}
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void hv_vss_deinit(void)
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{
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vss_transaction.state = HVUTIL_DEVICE_DYING;
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hv_vss_cancel_work();
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hvutil_transport_destroy(hvt);
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}
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