![Vitaly Kuznetsov](/assets/img/avatar_default.png)
When Hyper-V host asks us to remove some util driver by closing the appropriate channel there is no easy way to force the current file descriptor holder to hang up but we can start to respond -EBADF to all operations asking it to exit gracefully. As we're setting hvt->mode from two separate contexts now we need to use a proper locking. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
321 lines
7.1 KiB
C
321 lines
7.1 KiB
C
/*
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* Kernel/userspace transport abstraction for Hyper-V util driver.
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*
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* Copyright (C) 2015, Vitaly Kuznetsov <vkuznets@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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*/
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/poll.h>
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#include "hyperv_vmbus.h"
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#include "hv_utils_transport.h"
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static DEFINE_SPINLOCK(hvt_list_lock);
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static struct list_head hvt_list = LIST_HEAD_INIT(hvt_list);
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static void hvt_reset(struct hvutil_transport *hvt)
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{
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kfree(hvt->outmsg);
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hvt->outmsg = NULL;
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hvt->outmsg_len = 0;
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if (hvt->on_reset)
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hvt->on_reset();
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}
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static ssize_t hvt_op_read(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct hvutil_transport *hvt;
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int ret;
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hvt = container_of(file->f_op, struct hvutil_transport, fops);
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if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
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hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
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return -EINTR;
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mutex_lock(&hvt->lock);
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if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
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ret = -EBADF;
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goto out_unlock;
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}
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if (!hvt->outmsg) {
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ret = -EAGAIN;
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goto out_unlock;
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}
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if (count < hvt->outmsg_len) {
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ret = -EINVAL;
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goto out_unlock;
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}
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if (!copy_to_user(buf, hvt->outmsg, hvt->outmsg_len))
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ret = hvt->outmsg_len;
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else
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ret = -EFAULT;
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kfree(hvt->outmsg);
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hvt->outmsg = NULL;
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hvt->outmsg_len = 0;
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out_unlock:
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mutex_unlock(&hvt->lock);
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return ret;
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}
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static ssize_t hvt_op_write(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct hvutil_transport *hvt;
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u8 *inmsg;
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int ret;
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hvt = container_of(file->f_op, struct hvutil_transport, fops);
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inmsg = memdup_user(buf, count);
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if (IS_ERR(inmsg))
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return PTR_ERR(inmsg);
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if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
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ret = -EBADF;
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else
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ret = hvt->on_msg(inmsg, count);
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kfree(inmsg);
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return ret ? ret : count;
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}
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static unsigned int hvt_op_poll(struct file *file, poll_table *wait)
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{
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struct hvutil_transport *hvt;
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hvt = container_of(file->f_op, struct hvutil_transport, fops);
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poll_wait(file, &hvt->outmsg_q, wait);
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if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
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return -EBADF;
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if (hvt->outmsg_len > 0)
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return POLLIN | POLLRDNORM;
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return 0;
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}
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static int hvt_op_open(struct inode *inode, struct file *file)
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{
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struct hvutil_transport *hvt;
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int ret = 0;
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bool issue_reset = false;
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hvt = container_of(file->f_op, struct hvutil_transport, fops);
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mutex_lock(&hvt->lock);
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if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
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ret = -EBADF;
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} else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
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/*
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* Switching to CHARDEV mode. We switch bach to INIT when
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* device gets released.
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*/
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hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
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}
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else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
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/*
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* We're switching from netlink communication to using char
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* device. Issue the reset first.
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*/
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issue_reset = true;
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hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
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} else {
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ret = -EBUSY;
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}
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if (issue_reset)
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hvt_reset(hvt);
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mutex_unlock(&hvt->lock);
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return ret;
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}
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static int hvt_op_release(struct inode *inode, struct file *file)
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{
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struct hvutil_transport *hvt;
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hvt = container_of(file->f_op, struct hvutil_transport, fops);
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mutex_lock(&hvt->lock);
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if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
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hvt->mode = HVUTIL_TRANSPORT_INIT;
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/*
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* Cleanup message buffers to avoid spurious messages when the daemon
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* connects back.
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*/
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hvt_reset(hvt);
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mutex_unlock(&hvt->lock);
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return 0;
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}
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static void hvt_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
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{
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struct hvutil_transport *hvt, *hvt_found = NULL;
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spin_lock(&hvt_list_lock);
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list_for_each_entry(hvt, &hvt_list, list) {
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if (hvt->cn_id.idx == msg->id.idx &&
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hvt->cn_id.val == msg->id.val) {
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hvt_found = hvt;
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break;
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}
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}
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spin_unlock(&hvt_list_lock);
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if (!hvt_found) {
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pr_warn("hvt_cn_callback: spurious message received!\n");
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return;
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}
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/*
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* Switching to NETLINK mode. Switching to CHARDEV happens when someone
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* opens the device.
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*/
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mutex_lock(&hvt->lock);
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if (hvt->mode == HVUTIL_TRANSPORT_INIT)
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hvt->mode = HVUTIL_TRANSPORT_NETLINK;
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if (hvt->mode == HVUTIL_TRANSPORT_NETLINK)
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hvt_found->on_msg(msg->data, msg->len);
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else
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pr_warn("hvt_cn_callback: unexpected netlink message!\n");
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mutex_unlock(&hvt->lock);
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}
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int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
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{
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struct cn_msg *cn_msg;
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int ret = 0;
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if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
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hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
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return -EINVAL;
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} else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
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cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
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if (!cn_msg)
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return -ENOMEM;
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cn_msg->id.idx = hvt->cn_id.idx;
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cn_msg->id.val = hvt->cn_id.val;
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cn_msg->len = len;
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memcpy(cn_msg->data, msg, len);
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ret = cn_netlink_send(cn_msg, 0, 0, GFP_ATOMIC);
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kfree(cn_msg);
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return ret;
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}
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/* HVUTIL_TRANSPORT_CHARDEV */
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mutex_lock(&hvt->lock);
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if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
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ret = -EINVAL;
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goto out_unlock;
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}
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if (hvt->outmsg) {
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/* Previous message wasn't received */
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ret = -EFAULT;
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goto out_unlock;
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}
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hvt->outmsg = kzalloc(len, GFP_KERNEL);
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if (hvt->outmsg) {
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memcpy(hvt->outmsg, msg, len);
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hvt->outmsg_len = len;
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wake_up_interruptible(&hvt->outmsg_q);
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} else
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ret = -ENOMEM;
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out_unlock:
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mutex_unlock(&hvt->lock);
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return ret;
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}
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struct hvutil_transport *hvutil_transport_init(const char *name,
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u32 cn_idx, u32 cn_val,
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int (*on_msg)(void *, int),
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void (*on_reset)(void))
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{
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struct hvutil_transport *hvt;
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hvt = kzalloc(sizeof(*hvt), GFP_KERNEL);
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if (!hvt)
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return NULL;
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hvt->cn_id.idx = cn_idx;
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hvt->cn_id.val = cn_val;
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hvt->mdev.minor = MISC_DYNAMIC_MINOR;
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hvt->mdev.name = name;
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hvt->fops.owner = THIS_MODULE;
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hvt->fops.read = hvt_op_read;
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hvt->fops.write = hvt_op_write;
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hvt->fops.poll = hvt_op_poll;
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hvt->fops.open = hvt_op_open;
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hvt->fops.release = hvt_op_release;
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hvt->mdev.fops = &hvt->fops;
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init_waitqueue_head(&hvt->outmsg_q);
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mutex_init(&hvt->lock);
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spin_lock(&hvt_list_lock);
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list_add(&hvt->list, &hvt_list);
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spin_unlock(&hvt_list_lock);
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hvt->on_msg = on_msg;
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hvt->on_reset = on_reset;
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if (misc_register(&hvt->mdev))
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goto err_free_hvt;
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/* Use cn_id.idx/cn_id.val to determine if we need to setup netlink */
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if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0 &&
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cn_add_callback(&hvt->cn_id, name, hvt_cn_callback))
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goto err_free_hvt;
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return hvt;
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err_free_hvt:
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kfree(hvt);
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return NULL;
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}
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void hvutil_transport_destroy(struct hvutil_transport *hvt)
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{
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mutex_lock(&hvt->lock);
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hvt->mode = HVUTIL_TRANSPORT_DESTROY;
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wake_up_interruptible(&hvt->outmsg_q);
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mutex_unlock(&hvt->lock);
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spin_lock(&hvt_list_lock);
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list_del(&hvt->list);
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spin_unlock(&hvt_list_lock);
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if (hvt->cn_id.idx > 0 && hvt->cn_id.val > 0)
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cn_del_callback(&hvt->cn_id);
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misc_deregister(&hvt->mdev);
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kfree(hvt->outmsg);
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kfree(hvt);
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}
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