linux/drivers/xen/xenbus/xenbus_dev_frontend.c
Dan Carpenter 32ad11127b xen/xenbus: fix return type in xenbus_file_read()
This code tries to store -EFAULT in an unsigned int.  The
xenbus_file_read() function returns type ssize_t so the negative value
is returned as a positive value to the user.

This change forces another change to the min() macro.  Originally, the
min() macro used "unsigned" type which checkpatch complains about.  Also
unsigned type would break if "len" were not capped at MAX_RW_COUNT.  Use
size_t for the min().  (No effect on runtime for the min_t() change).

Fixes: 2fb3683e7b ("xen: Add xenbus device driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Link: https://lore.kernel.org/r/YutxJUaUYRG/VLVc@kili
Signed-off-by: Juergen Gross <jgross@suse.com>
2022-08-12 12:16:39 +02:00

726 lines
17 KiB
C

/*
* Driver giving user-space access to the kernel's xenbus connection
* to xenstore.
*
* Copyright (c) 2005, Christian Limpach
* Copyright (c) 2005, Rusty Russell, IBM Corporation
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* Changes:
* 2008-10-07 Alex Zeffertt Replaced /proc/xen/xenbus with xenfs filesystem
* and /proc/xen compatibility mount point.
* Turned xenfs into a loadable module.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/uio.h>
#include <linux/notifier.h>
#include <linux/wait.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/uaccess.h>
#include <linux/init.h>
#include <linux/namei.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/miscdevice.h>
#include <linux/workqueue.h>
#include <xen/xenbus.h>
#include <xen/xen.h>
#include <asm/xen/hypervisor.h>
#include "xenbus.h"
unsigned int xb_dev_generation_id;
/*
* An element of a list of outstanding transactions, for which we're
* still waiting a reply.
*/
struct xenbus_transaction_holder {
struct list_head list;
struct xenbus_transaction handle;
unsigned int generation_id;
};
/*
* A buffer of data on the queue.
*/
struct read_buffer {
struct list_head list;
unsigned int cons;
unsigned int len;
char msg[];
};
struct xenbus_file_priv {
/*
* msgbuffer_mutex is held while partial requests are built up
* and complete requests are acted on. It therefore protects
* the "transactions" and "watches" lists, and the partial
* request length and buffer.
*
* reply_mutex protects the reply being built up to return to
* usermode. It nests inside msgbuffer_mutex but may be held
* alone during a watch callback.
*/
struct mutex msgbuffer_mutex;
/* In-progress transactions */
struct list_head transactions;
/* Active watches. */
struct list_head watches;
/* Partial request. */
unsigned int len;
union {
struct xsd_sockmsg msg;
char buffer[XENSTORE_PAYLOAD_MAX];
} u;
/* Response queue. */
struct mutex reply_mutex;
struct list_head read_buffers;
wait_queue_head_t read_waitq;
struct kref kref;
struct work_struct wq;
};
/* Read out any raw xenbus messages queued up. */
static ssize_t xenbus_file_read(struct file *filp,
char __user *ubuf,
size_t len, loff_t *ppos)
{
struct xenbus_file_priv *u = filp->private_data;
struct read_buffer *rb;
ssize_t i;
int ret;
mutex_lock(&u->reply_mutex);
again:
while (list_empty(&u->read_buffers)) {
mutex_unlock(&u->reply_mutex);
if (filp->f_flags & O_NONBLOCK)
return -EAGAIN;
ret = wait_event_interruptible(u->read_waitq,
!list_empty(&u->read_buffers));
if (ret)
return ret;
mutex_lock(&u->reply_mutex);
}
rb = list_entry(u->read_buffers.next, struct read_buffer, list);
i = 0;
while (i < len) {
size_t sz = min_t(size_t, len - i, rb->len - rb->cons);
ret = copy_to_user(ubuf + i, &rb->msg[rb->cons], sz);
i += sz - ret;
rb->cons += sz - ret;
if (ret != 0) {
if (i == 0)
i = -EFAULT;
goto out;
}
/* Clear out buffer if it has been consumed */
if (rb->cons == rb->len) {
list_del(&rb->list);
kfree(rb);
if (list_empty(&u->read_buffers))
break;
rb = list_entry(u->read_buffers.next,
struct read_buffer, list);
}
}
if (i == 0)
goto again;
out:
mutex_unlock(&u->reply_mutex);
return i;
}
/*
* Add a buffer to the queue. Caller must hold the appropriate lock
* if the queue is not local. (Commonly the caller will build up
* multiple queued buffers on a temporary local list, and then add it
* to the appropriate list under lock once all the buffers have een
* successfully allocated.)
*/
static int queue_reply(struct list_head *queue, const void *data, size_t len)
{
struct read_buffer *rb;
if (len == 0)
return 0;
if (len > XENSTORE_PAYLOAD_MAX)
return -EINVAL;
rb = kmalloc(sizeof(*rb) + len, GFP_KERNEL);
if (rb == NULL)
return -ENOMEM;
rb->cons = 0;
rb->len = len;
memcpy(rb->msg, data, len);
list_add_tail(&rb->list, queue);
return 0;
}
/*
* Free all the read_buffer s on a list.
* Caller must have sole reference to list.
*/
static void queue_cleanup(struct list_head *list)
{
struct read_buffer *rb;
while (!list_empty(list)) {
rb = list_entry(list->next, struct read_buffer, list);
list_del(list->next);
kfree(rb);
}
}
struct watch_adapter {
struct list_head list;
struct xenbus_watch watch;
struct xenbus_file_priv *dev_data;
char *token;
};
static void free_watch_adapter(struct watch_adapter *watch)
{
kfree(watch->watch.node);
kfree(watch->token);
kfree(watch);
}
static struct watch_adapter *alloc_watch_adapter(const char *path,
const char *token)
{
struct watch_adapter *watch;
watch = kzalloc(sizeof(*watch), GFP_KERNEL);
if (watch == NULL)
goto out_fail;
watch->watch.node = kstrdup(path, GFP_KERNEL);
if (watch->watch.node == NULL)
goto out_free;
watch->token = kstrdup(token, GFP_KERNEL);
if (watch->token == NULL)
goto out_free;
return watch;
out_free:
free_watch_adapter(watch);
out_fail:
return NULL;
}
static void watch_fired(struct xenbus_watch *watch,
const char *path,
const char *token)
{
struct watch_adapter *adap;
struct xsd_sockmsg hdr;
const char *token_caller;
int path_len, tok_len, body_len;
int ret;
LIST_HEAD(staging_q);
adap = container_of(watch, struct watch_adapter, watch);
token_caller = adap->token;
path_len = strlen(path) + 1;
tok_len = strlen(token_caller) + 1;
body_len = path_len + tok_len;
hdr.type = XS_WATCH_EVENT;
hdr.len = body_len;
mutex_lock(&adap->dev_data->reply_mutex);
ret = queue_reply(&staging_q, &hdr, sizeof(hdr));
if (!ret)
ret = queue_reply(&staging_q, path, path_len);
if (!ret)
ret = queue_reply(&staging_q, token_caller, tok_len);
if (!ret) {
/* success: pass reply list onto watcher */
list_splice_tail(&staging_q, &adap->dev_data->read_buffers);
wake_up(&adap->dev_data->read_waitq);
} else
queue_cleanup(&staging_q);
mutex_unlock(&adap->dev_data->reply_mutex);
}
static void xenbus_worker(struct work_struct *wq)
{
struct xenbus_file_priv *u;
struct xenbus_transaction_holder *trans, *tmp;
struct watch_adapter *watch, *tmp_watch;
struct read_buffer *rb, *tmp_rb;
u = container_of(wq, struct xenbus_file_priv, wq);
/*
* No need for locking here because there are no other users,
* by definition.
*/
list_for_each_entry_safe(trans, tmp, &u->transactions, list) {
xenbus_transaction_end(trans->handle, 1);
list_del(&trans->list);
kfree(trans);
}
list_for_each_entry_safe(watch, tmp_watch, &u->watches, list) {
unregister_xenbus_watch(&watch->watch);
list_del(&watch->list);
free_watch_adapter(watch);
}
list_for_each_entry_safe(rb, tmp_rb, &u->read_buffers, list) {
list_del(&rb->list);
kfree(rb);
}
kfree(u);
}
static void xenbus_file_free(struct kref *kref)
{
struct xenbus_file_priv *u;
/*
* We might be called in xenbus_thread().
* Use workqueue to avoid deadlock.
*/
u = container_of(kref, struct xenbus_file_priv, kref);
schedule_work(&u->wq);
}
static struct xenbus_transaction_holder *xenbus_get_transaction(
struct xenbus_file_priv *u, uint32_t tx_id)
{
struct xenbus_transaction_holder *trans;
list_for_each_entry(trans, &u->transactions, list)
if (trans->handle.id == tx_id)
return trans;
return NULL;
}
void xenbus_dev_queue_reply(struct xb_req_data *req)
{
struct xenbus_file_priv *u = req->par;
struct xenbus_transaction_holder *trans = NULL;
int rc;
LIST_HEAD(staging_q);
xs_request_exit(req);
mutex_lock(&u->msgbuffer_mutex);
if (req->type == XS_TRANSACTION_START) {
trans = xenbus_get_transaction(u, 0);
if (WARN_ON(!trans))
goto out;
if (req->msg.type == XS_ERROR) {
list_del(&trans->list);
kfree(trans);
} else {
rc = kstrtou32(req->body, 10, &trans->handle.id);
if (WARN_ON(rc))
goto out;
}
} else if (req->type == XS_TRANSACTION_END) {
trans = xenbus_get_transaction(u, req->msg.tx_id);
if (WARN_ON(!trans))
goto out;
list_del(&trans->list);
kfree(trans);
}
mutex_unlock(&u->msgbuffer_mutex);
mutex_lock(&u->reply_mutex);
rc = queue_reply(&staging_q, &req->msg, sizeof(req->msg));
if (!rc)
rc = queue_reply(&staging_q, req->body, req->msg.len);
if (!rc) {
list_splice_tail(&staging_q, &u->read_buffers);
wake_up(&u->read_waitq);
} else {
queue_cleanup(&staging_q);
}
mutex_unlock(&u->reply_mutex);
kfree(req->body);
kfree(req);
kref_put(&u->kref, xenbus_file_free);
return;
out:
mutex_unlock(&u->msgbuffer_mutex);
}
static int xenbus_command_reply(struct xenbus_file_priv *u,
unsigned int msg_type, const char *reply)
{
struct {
struct xsd_sockmsg hdr;
char body[16];
} msg;
int rc;
msg.hdr = u->u.msg;
msg.hdr.type = msg_type;
msg.hdr.len = strlen(reply) + 1;
if (msg.hdr.len > sizeof(msg.body))
return -E2BIG;
memcpy(&msg.body, reply, msg.hdr.len);
mutex_lock(&u->reply_mutex);
rc = queue_reply(&u->read_buffers, &msg, sizeof(msg.hdr) + msg.hdr.len);
wake_up(&u->read_waitq);
mutex_unlock(&u->reply_mutex);
if (!rc)
kref_put(&u->kref, xenbus_file_free);
return rc;
}
static int xenbus_write_transaction(unsigned msg_type,
struct xenbus_file_priv *u)
{
int rc;
struct xenbus_transaction_holder *trans = NULL;
struct {
struct xsd_sockmsg hdr;
char body[];
} *msg = (void *)u->u.buffer;
if (msg_type == XS_TRANSACTION_START) {
trans = kzalloc(sizeof(*trans), GFP_KERNEL);
if (!trans) {
rc = -ENOMEM;
goto out;
}
trans->generation_id = xb_dev_generation_id;
list_add(&trans->list, &u->transactions);
} else if (msg->hdr.tx_id != 0 &&
!xenbus_get_transaction(u, msg->hdr.tx_id))
return xenbus_command_reply(u, XS_ERROR, "ENOENT");
else if (msg_type == XS_TRANSACTION_END &&
!(msg->hdr.len == 2 &&
(!strcmp(msg->body, "T") || !strcmp(msg->body, "F"))))
return xenbus_command_reply(u, XS_ERROR, "EINVAL");
else if (msg_type == XS_TRANSACTION_END) {
trans = xenbus_get_transaction(u, msg->hdr.tx_id);
if (trans && trans->generation_id != xb_dev_generation_id) {
list_del(&trans->list);
kfree(trans);
if (!strcmp(msg->body, "T"))
return xenbus_command_reply(u, XS_ERROR,
"EAGAIN");
else
return xenbus_command_reply(u,
XS_TRANSACTION_END,
"OK");
}
}
rc = xenbus_dev_request_and_reply(&msg->hdr, u);
if (rc && trans) {
list_del(&trans->list);
kfree(trans);
}
out:
return rc;
}
static int xenbus_write_watch(unsigned msg_type, struct xenbus_file_priv *u)
{
struct watch_adapter *watch;
char *path, *token;
int err, rc;
path = u->u.buffer + sizeof(u->u.msg);
token = memchr(path, 0, u->u.msg.len);
if (token == NULL) {
rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
goto out;
}
token++;
if (memchr(token, 0, u->u.msg.len - (token - path)) == NULL) {
rc = xenbus_command_reply(u, XS_ERROR, "EINVAL");
goto out;
}
if (msg_type == XS_WATCH) {
watch = alloc_watch_adapter(path, token);
if (watch == NULL) {
rc = -ENOMEM;
goto out;
}
watch->watch.callback = watch_fired;
watch->dev_data = u;
err = register_xenbus_watch(&watch->watch);
if (err) {
free_watch_adapter(watch);
rc = err;
goto out;
}
list_add(&watch->list, &u->watches);
} else {
list_for_each_entry(watch, &u->watches, list) {
if (!strcmp(watch->token, token) &&
!strcmp(watch->watch.node, path)) {
unregister_xenbus_watch(&watch->watch);
list_del(&watch->list);
free_watch_adapter(watch);
break;
}
}
}
/* Success. Synthesize a reply to say all is OK. */
rc = xenbus_command_reply(u, msg_type, "OK");
out:
return rc;
}
static ssize_t xenbus_file_write(struct file *filp,
const char __user *ubuf,
size_t len, loff_t *ppos)
{
struct xenbus_file_priv *u = filp->private_data;
uint32_t msg_type;
int rc = len;
int ret;
/*
* We're expecting usermode to be writing properly formed
* xenbus messages. If they write an incomplete message we
* buffer it up. Once it is complete, we act on it.
*/
/*
* Make sure concurrent writers can't stomp all over each
* other's messages and make a mess of our partial message
* buffer. We don't make any attemppt to stop multiple
* writers from making a mess of each other's incomplete
* messages; we're just trying to guarantee our own internal
* consistency and make sure that single writes are handled
* atomically.
*/
mutex_lock(&u->msgbuffer_mutex);
/* Get this out of the way early to avoid confusion */
if (len == 0)
goto out;
/* Can't write a xenbus message larger we can buffer */
if (len > sizeof(u->u.buffer) - u->len) {
/* On error, dump existing buffer */
u->len = 0;
rc = -EINVAL;
goto out;
}
ret = copy_from_user(u->u.buffer + u->len, ubuf, len);
if (ret != 0) {
rc = -EFAULT;
goto out;
}
/* Deal with a partial copy. */
len -= ret;
rc = len;
u->len += len;
/* Return if we haven't got a full message yet */
if (u->len < sizeof(u->u.msg))
goto out; /* not even the header yet */
/* If we're expecting a message that's larger than we can
possibly send, dump what we have and return an error. */
if ((sizeof(u->u.msg) + u->u.msg.len) > sizeof(u->u.buffer)) {
rc = -E2BIG;
u->len = 0;
goto out;
}
if (u->len < (sizeof(u->u.msg) + u->u.msg.len))
goto out; /* incomplete data portion */
/*
* OK, now we have a complete message. Do something with it.
*/
kref_get(&u->kref);
msg_type = u->u.msg.type;
switch (msg_type) {
case XS_WATCH:
case XS_UNWATCH:
/* (Un)Ask for some path to be watched for changes */
ret = xenbus_write_watch(msg_type, u);
break;
default:
/* Send out a transaction */
ret = xenbus_write_transaction(msg_type, u);
break;
}
if (ret != 0) {
rc = ret;
kref_put(&u->kref, xenbus_file_free);
}
/* Buffered message consumed */
u->len = 0;
out:
mutex_unlock(&u->msgbuffer_mutex);
return rc;
}
static int xenbus_file_open(struct inode *inode, struct file *filp)
{
struct xenbus_file_priv *u;
if (xen_store_evtchn == 0)
return -ENOENT;
stream_open(inode, filp);
u = kzalloc(sizeof(*u), GFP_KERNEL);
if (u == NULL)
return -ENOMEM;
kref_init(&u->kref);
INIT_LIST_HEAD(&u->transactions);
INIT_LIST_HEAD(&u->watches);
INIT_LIST_HEAD(&u->read_buffers);
init_waitqueue_head(&u->read_waitq);
INIT_WORK(&u->wq, xenbus_worker);
mutex_init(&u->reply_mutex);
mutex_init(&u->msgbuffer_mutex);
filp->private_data = u;
return 0;
}
static int xenbus_file_release(struct inode *inode, struct file *filp)
{
struct xenbus_file_priv *u = filp->private_data;
kref_put(&u->kref, xenbus_file_free);
return 0;
}
static __poll_t xenbus_file_poll(struct file *file, poll_table *wait)
{
struct xenbus_file_priv *u = file->private_data;
poll_wait(file, &u->read_waitq, wait);
if (!list_empty(&u->read_buffers))
return EPOLLIN | EPOLLRDNORM;
return 0;
}
const struct file_operations xen_xenbus_fops = {
.read = xenbus_file_read,
.write = xenbus_file_write,
.open = xenbus_file_open,
.release = xenbus_file_release,
.poll = xenbus_file_poll,
.llseek = no_llseek,
};
EXPORT_SYMBOL_GPL(xen_xenbus_fops);
static struct miscdevice xenbus_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "xen/xenbus",
.fops = &xen_xenbus_fops,
};
static int __init xenbus_init(void)
{
int err;
if (!xen_domain())
return -ENODEV;
err = misc_register(&xenbus_dev);
if (err)
pr_err("Could not register xenbus frontend device\n");
return err;
}
device_initcall(xenbus_init);