| /* |
| * CUSE: Character device in Userspace |
| * |
| * Copyright (C) 2008-2009 SUSE Linux Products GmbH |
| * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org> |
| * |
| * This file is released under the GPLv2. |
| * |
| * CUSE enables character devices to be implemented from userland much |
| * like FUSE allows filesystems. On initialization /dev/cuse is |
| * created. By opening the file and replying to the CUSE_INIT request |
| * userland CUSE server can create a character device. After that the |
| * operation is very similar to FUSE. |
| * |
| * A CUSE instance involves the following objects. |
| * |
| * cuse_conn : contains fuse_conn and serves as bonding structure |
| * channel : file handle connected to the userland CUSE server |
| * cdev : the implemented character device |
| * dev : generic device for cdev |
| * |
| * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with |
| * devices, it's called 'channel' to reduce confusion. |
| * |
| * channel determines when the character device dies. When channel is |
| * closed, everything begins to destruct. The cuse_conn is taken off |
| * the lookup table preventing further access from cdev, cdev and |
| * generic device are removed and the base reference of cuse_conn is |
| * put. |
| * |
| * On each open, the matching cuse_conn is looked up and if found an |
| * additional reference is taken which is released when the file is |
| * closed. |
| */ |
| |
| #define pr_fmt(fmt) "CUSE: " fmt |
| |
| #include <linux/fuse.h> |
| #include <linux/cdev.h> |
| #include <linux/device.h> |
| #include <linux/file.h> |
| #include <linux/fs.h> |
| #include <linux/kdev_t.h> |
| #include <linux/kthread.h> |
| #include <linux/list.h> |
| #include <linux/magic.h> |
| #include <linux/miscdevice.h> |
| #include <linux/mutex.h> |
| #include <linux/slab.h> |
| #include <linux/stat.h> |
| #include <linux/module.h> |
| #include <linux/uio.h> |
| #include <linux/user_namespace.h> |
| |
| #include "fuse_i.h" |
| |
| #define CUSE_CONNTBL_LEN 64 |
| |
| struct cuse_conn { |
| struct list_head list; /* linked on cuse_conntbl */ |
| struct fuse_conn fc; /* fuse connection */ |
| struct cdev *cdev; /* associated character device */ |
| struct device *dev; /* device representing @cdev */ |
| |
| /* init parameters, set once during initialization */ |
| bool unrestricted_ioctl; |
| }; |
| |
| static DEFINE_MUTEX(cuse_lock); /* protects registration */ |
| static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN]; |
| static struct class *cuse_class; |
| |
| static struct cuse_conn *fc_to_cc(struct fuse_conn *fc) |
| { |
| return container_of(fc, struct cuse_conn, fc); |
| } |
| |
| static struct list_head *cuse_conntbl_head(dev_t devt) |
| { |
| return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN]; |
| } |
| |
| |
| /************************************************************************** |
| * CUSE frontend operations |
| * |
| * These are file operations for the character device. |
| * |
| * On open, CUSE opens a file from the FUSE mnt and stores it to |
| * private_data of the open file. All other ops call FUSE ops on the |
| * FUSE file. |
| */ |
| |
| static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to) |
| { |
| struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb); |
| loff_t pos = 0; |
| |
| return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE); |
| } |
| |
| static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from) |
| { |
| struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb); |
| loff_t pos = 0; |
| /* |
| * No locking or generic_write_checks(), the server is |
| * responsible for locking and sanity checks. |
| */ |
| return fuse_direct_io(&io, from, &pos, |
| FUSE_DIO_WRITE | FUSE_DIO_CUSE); |
| } |
| |
| static int cuse_open(struct inode *inode, struct file *file) |
| { |
| dev_t devt = inode->i_cdev->dev; |
| struct cuse_conn *cc = NULL, *pos; |
| int rc; |
| |
| /* look up and get the connection */ |
| mutex_lock(&cuse_lock); |
| list_for_each_entry(pos, cuse_conntbl_head(devt), list) |
| if (pos->dev->devt == devt) { |
| fuse_conn_get(&pos->fc); |
| cc = pos; |
| break; |
| } |
| mutex_unlock(&cuse_lock); |
| |
| /* dead? */ |
| if (!cc) |
| return -ENODEV; |
| |
| /* |
| * Generic permission check is already done against the chrdev |
| * file, proceed to open. |
| */ |
| rc = fuse_do_open(&cc->fc, 0, file, 0); |
| if (rc) |
| fuse_conn_put(&cc->fc); |
| return rc; |
| } |
| |
| static int cuse_release(struct inode *inode, struct file *file) |
| { |
| struct fuse_inode *fi = get_fuse_inode(inode); |
| struct fuse_file *ff = file->private_data; |
| struct fuse_conn *fc = ff->fc; |
| |
| fuse_sync_release(fi, ff, file->f_flags); |
| fuse_conn_put(fc); |
| |
| return 0; |
| } |
| |
| static long cuse_file_ioctl(struct file *file, unsigned int cmd, |
| unsigned long arg) |
| { |
| struct fuse_file *ff = file->private_data; |
| struct cuse_conn *cc = fc_to_cc(ff->fc); |
| unsigned int flags = 0; |
| |
| if (cc->unrestricted_ioctl) |
| flags |= FUSE_IOCTL_UNRESTRICTED; |
| |
| return fuse_do_ioctl(file, cmd, arg, flags); |
| } |
| |
| static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd, |
| unsigned long arg) |
| { |
| struct fuse_file *ff = file->private_data; |
| struct cuse_conn *cc = fc_to_cc(ff->fc); |
| unsigned int flags = FUSE_IOCTL_COMPAT; |
| |
| if (cc->unrestricted_ioctl) |
| flags |= FUSE_IOCTL_UNRESTRICTED; |
| |
| return fuse_do_ioctl(file, cmd, arg, flags); |
| } |
| |
| static const struct file_operations cuse_frontend_fops = { |
| .owner = THIS_MODULE, |
| .read_iter = cuse_read_iter, |
| .write_iter = cuse_write_iter, |
| .open = cuse_open, |
| .release = cuse_release, |
| .unlocked_ioctl = cuse_file_ioctl, |
| .compat_ioctl = cuse_file_compat_ioctl, |
| .poll = fuse_file_poll, |
| .llseek = noop_llseek, |
| }; |
| |
| |
| /************************************************************************** |
| * CUSE channel initialization and destruction |
| */ |
| |
| struct cuse_devinfo { |
| const char *name; |
| }; |
| |
| /** |
| * cuse_parse_one - parse one key=value pair |
| * @pp: i/o parameter for the current position |
| * @end: points to one past the end of the packed string |
| * @keyp: out parameter for key |
| * @valp: out parameter for value |
| * |
| * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends |
| * at @end - 1. This function parses one pair and set *@keyp to the |
| * start of the key and *@valp to the start of the value. Note that |
| * the original string is modified such that the key string is |
| * terminated with '\0'. *@pp is updated to point to the next string. |
| * |
| * RETURNS: |
| * 1 on successful parse, 0 on EOF, -errno on failure. |
| */ |
| static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp) |
| { |
| char *p = *pp; |
| char *key, *val; |
| |
| while (p < end && *p == '\0') |
| p++; |
| if (p == end) |
| return 0; |
| |
| if (end[-1] != '\0') { |
| pr_err("info not properly terminated\n"); |
| return -EINVAL; |
| } |
| |
| key = val = p; |
| p += strlen(p); |
| |
| if (valp) { |
| strsep(&val, "="); |
| if (!val) |
| val = key + strlen(key); |
| key = strstrip(key); |
| val = strstrip(val); |
| } else |
| key = strstrip(key); |
| |
| if (!strlen(key)) { |
| pr_err("zero length info key specified\n"); |
| return -EINVAL; |
| } |
| |
| *pp = p; |
| *keyp = key; |
| if (valp) |
| *valp = val; |
| |
| return 1; |
| } |
| |
| /** |
| * cuse_parse_dev_info - parse device info |
| * @p: device info string |
| * @len: length of device info string |
| * @devinfo: out parameter for parsed device info |
| * |
| * Parse @p to extract device info and store it into @devinfo. String |
| * pointed to by @p is modified by parsing and @devinfo points into |
| * them, so @p shouldn't be freed while @devinfo is in use. |
| * |
| * RETURNS: |
| * 0 on success, -errno on failure. |
| */ |
| static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo) |
| { |
| char *end = p + len; |
| char *uninitialized_var(key), *uninitialized_var(val); |
| int rc; |
| |
| while (true) { |
| rc = cuse_parse_one(&p, end, &key, &val); |
| if (rc < 0) |
| return rc; |
| if (!rc) |
| break; |
| if (strcmp(key, "DEVNAME") == 0) |
| devinfo->name = val; |
| else |
| pr_warn("unknown device info \"%s\"\n", key); |
| } |
| |
| if (!devinfo->name || !strlen(devinfo->name)) { |
| pr_err("DEVNAME unspecified\n"); |
| return -EINVAL; |
| } |
| |
| return 0; |
| } |
| |
| static void cuse_gendev_release(struct device *dev) |
| { |
| kfree(dev); |
| } |
| |
| /** |
| * cuse_process_init_reply - finish initializing CUSE channel |
| * |
| * This function creates the character device and sets up all the |
| * required data structures for it. Please read the comment at the |
| * top of this file for high level overview. |
| */ |
| static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req) |
| { |
| struct cuse_conn *cc = fc_to_cc(fc), *pos; |
| struct cuse_init_out *arg = req->out.args[0].value; |
| struct page *page = req->pages[0]; |
| struct cuse_devinfo devinfo = { }; |
| struct device *dev; |
| struct cdev *cdev; |
| dev_t devt; |
| int rc, i; |
| |
| if (req->out.h.error || |
| arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) { |
| goto err; |
| } |
| |
| fc->minor = arg->minor; |
| fc->max_read = max_t(unsigned, arg->max_read, 4096); |
| fc->max_write = max_t(unsigned, arg->max_write, 4096); |
| |
| /* parse init reply */ |
| cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL; |
| |
| rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size, |
| &devinfo); |
| if (rc) |
| goto err; |
| |
| /* determine and reserve devt */ |
| devt = MKDEV(arg->dev_major, arg->dev_minor); |
| if (!MAJOR(devt)) |
| rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name); |
| else |
| rc = register_chrdev_region(devt, 1, devinfo.name); |
| if (rc) { |
| pr_err("failed to register chrdev region\n"); |
| goto err; |
| } |
| |
| /* devt determined, create device */ |
| rc = -ENOMEM; |
| dev = kzalloc(sizeof(*dev), GFP_KERNEL); |
| if (!dev) |
| goto err_region; |
| |
| device_initialize(dev); |
| dev_set_uevent_suppress(dev, 1); |
| dev->class = cuse_class; |
| dev->devt = devt; |
| dev->release = cuse_gendev_release; |
| dev_set_drvdata(dev, cc); |
| dev_set_name(dev, "%s", devinfo.name); |
| |
| mutex_lock(&cuse_lock); |
| |
| /* make sure the device-name is unique */ |
| for (i = 0; i < CUSE_CONNTBL_LEN; ++i) { |
| list_for_each_entry(pos, &cuse_conntbl[i], list) |
| if (!strcmp(dev_name(pos->dev), dev_name(dev))) |
| goto err_unlock; |
| } |
| |
| rc = device_add(dev); |
| if (rc) |
| goto err_unlock; |
| |
| /* register cdev */ |
| rc = -ENOMEM; |
| cdev = cdev_alloc(); |
| if (!cdev) |
| goto err_unlock; |
| |
| cdev->owner = THIS_MODULE; |
| cdev->ops = &cuse_frontend_fops; |
| |
| rc = cdev_add(cdev, devt, 1); |
| if (rc) |
| goto err_cdev; |
| |
| cc->dev = dev; |
| cc->cdev = cdev; |
| |
| /* make the device available */ |
| list_add(&cc->list, cuse_conntbl_head(devt)); |
| mutex_unlock(&cuse_lock); |
| |
| /* announce device availability */ |
| dev_set_uevent_suppress(dev, 0); |
| kobject_uevent(&dev->kobj, KOBJ_ADD); |
| out: |
| kfree(arg); |
| __free_page(page); |
| return; |
| |
| err_cdev: |
| cdev_del(cdev); |
| err_unlock: |
| mutex_unlock(&cuse_lock); |
| put_device(dev); |
| err_region: |
| unregister_chrdev_region(devt, 1); |
| err: |
| fuse_abort_conn(fc); |
| goto out; |
| } |
| |
| static int cuse_send_init(struct cuse_conn *cc) |
| { |
| int rc; |
| struct fuse_req *req; |
| struct page *page; |
| struct fuse_conn *fc = &cc->fc; |
| struct cuse_init_in *arg; |
| void *outarg; |
| |
| BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE); |
| |
| req = fuse_get_req_for_background(fc, 1); |
| if (IS_ERR(req)) { |
| rc = PTR_ERR(req); |
| goto err; |
| } |
| |
| rc = -ENOMEM; |
| page = alloc_page(GFP_KERNEL | __GFP_ZERO); |
| if (!page) |
| goto err_put_req; |
| |
| outarg = kzalloc(sizeof(struct cuse_init_out), GFP_KERNEL); |
| if (!outarg) |
| goto err_free_page; |
| |
| arg = &req->misc.cuse_init_in; |
| arg->major = FUSE_KERNEL_VERSION; |
| arg->minor = FUSE_KERNEL_MINOR_VERSION; |
| arg->flags |= CUSE_UNRESTRICTED_IOCTL; |
| req->in.h.opcode = CUSE_INIT; |
| req->in.numargs = 1; |
| req->in.args[0].size = sizeof(struct cuse_init_in); |
| req->in.args[0].value = arg; |
| req->out.numargs = 2; |
| req->out.args[0].size = sizeof(struct cuse_init_out); |
| req->out.args[0].value = outarg; |
| req->out.args[1].size = CUSE_INIT_INFO_MAX; |
| req->out.argvar = 1; |
| req->out.argpages = 1; |
| req->pages[0] = page; |
| req->page_descs[0].length = req->out.args[1].size; |
| req->num_pages = 1; |
| req->end = cuse_process_init_reply; |
| fuse_request_send_background(fc, req); |
| |
| return 0; |
| |
| err_free_page: |
| __free_page(page); |
| err_put_req: |
| fuse_put_request(fc, req); |
| err: |
| return rc; |
| } |
| |
| static void cuse_fc_release(struct fuse_conn *fc) |
| { |
| struct cuse_conn *cc = fc_to_cc(fc); |
| kfree_rcu(cc, fc.rcu); |
| } |
| |
| /** |
| * cuse_channel_open - open method for /dev/cuse |
| * @inode: inode for /dev/cuse |
| * @file: file struct being opened |
| * |
| * Userland CUSE server can create a CUSE device by opening /dev/cuse |
| * and replying to the initialization request kernel sends. This |
| * function is responsible for handling CUSE device initialization. |
| * Because the fd opened by this function is used during |
| * initialization, this function only creates cuse_conn and sends |
| * init. The rest is delegated to a kthread. |
| * |
| * RETURNS: |
| * 0 on success, -errno on failure. |
| */ |
| static int cuse_channel_open(struct inode *inode, struct file *file) |
| { |
| struct fuse_dev *fud; |
| struct cuse_conn *cc; |
| int rc; |
| |
| /* set up cuse_conn */ |
| cc = kzalloc(sizeof(*cc), GFP_KERNEL); |
| if (!cc) |
| return -ENOMEM; |
| |
| /* |
| * Limit the cuse channel to requests that can |
| * be represented in file->f_cred->user_ns. |
| */ |
| fuse_conn_init(&cc->fc, file->f_cred->user_ns); |
| |
| fud = fuse_dev_alloc(&cc->fc); |
| if (!fud) { |
| kfree(cc); |
| return -ENOMEM; |
| } |
| |
| INIT_LIST_HEAD(&cc->list); |
| cc->fc.release = cuse_fc_release; |
| |
| cc->fc.initialized = 1; |
| rc = cuse_send_init(cc); |
| if (rc) { |
| fuse_dev_free(fud); |
| return rc; |
| } |
| file->private_data = fud; |
| |
| return 0; |
| } |
| |
| /** |
| * cuse_channel_release - release method for /dev/cuse |
| * @inode: inode for /dev/cuse |
| * @file: file struct being closed |
| * |
| * Disconnect the channel, deregister CUSE device and initiate |
| * destruction by putting the default reference. |
| * |
| * RETURNS: |
| * 0 on success, -errno on failure. |
| */ |
| static int cuse_channel_release(struct inode *inode, struct file *file) |
| { |
| struct fuse_dev *fud = file->private_data; |
| struct cuse_conn *cc = fc_to_cc(fud->fc); |
| int rc; |
| |
| /* remove from the conntbl, no more access from this point on */ |
| mutex_lock(&cuse_lock); |
| list_del_init(&cc->list); |
| mutex_unlock(&cuse_lock); |
| |
| /* remove device */ |
| if (cc->dev) |
| device_unregister(cc->dev); |
| if (cc->cdev) { |
| unregister_chrdev_region(cc->cdev->dev, 1); |
| cdev_del(cc->cdev); |
| } |
| /* Base reference is now owned by "fud" */ |
| fuse_conn_put(&cc->fc); |
| |
| rc = fuse_dev_release(inode, file); /* puts the base reference */ |
| |
| return rc; |
| } |
| |
| static struct file_operations cuse_channel_fops; /* initialized during init */ |
| |
| |
| /************************************************************************** |
| * Misc stuff and module initializatiion |
| * |
| * CUSE exports the same set of attributes to sysfs as fusectl. |
| */ |
| |
| static ssize_t cuse_class_waiting_show(struct device *dev, |
| struct device_attribute *attr, char *buf) |
| { |
| struct cuse_conn *cc = dev_get_drvdata(dev); |
| |
| return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting)); |
| } |
| static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL); |
| |
| static ssize_t cuse_class_abort_store(struct device *dev, |
| struct device_attribute *attr, |
| const char *buf, size_t count) |
| { |
| struct cuse_conn *cc = dev_get_drvdata(dev); |
| |
| fuse_abort_conn(&cc->fc); |
| return count; |
| } |
| static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store); |
| |
| static struct attribute *cuse_class_dev_attrs[] = { |
| &dev_attr_waiting.attr, |
| &dev_attr_abort.attr, |
| NULL, |
| }; |
| ATTRIBUTE_GROUPS(cuse_class_dev); |
| |
| static struct miscdevice cuse_miscdev = { |
| .minor = CUSE_MINOR, |
| .name = "cuse", |
| .fops = &cuse_channel_fops, |
| }; |
| |
| MODULE_ALIAS_MISCDEV(CUSE_MINOR); |
| MODULE_ALIAS("devname:cuse"); |
| |
| static int __init cuse_init(void) |
| { |
| int i, rc; |
| |
| /* init conntbl */ |
| for (i = 0; i < CUSE_CONNTBL_LEN; i++) |
| INIT_LIST_HEAD(&cuse_conntbl[i]); |
| |
| /* inherit and extend fuse_dev_operations */ |
| cuse_channel_fops = fuse_dev_operations; |
| cuse_channel_fops.owner = THIS_MODULE; |
| cuse_channel_fops.open = cuse_channel_open; |
| cuse_channel_fops.release = cuse_channel_release; |
| |
| cuse_class = class_create(THIS_MODULE, "cuse"); |
| if (IS_ERR(cuse_class)) |
| return PTR_ERR(cuse_class); |
| |
| cuse_class->dev_groups = cuse_class_dev_groups; |
| |
| rc = misc_register(&cuse_miscdev); |
| if (rc) { |
| class_destroy(cuse_class); |
| return rc; |
| } |
| |
| return 0; |
| } |
| |
| static void __exit cuse_exit(void) |
| { |
| misc_deregister(&cuse_miscdev); |
| class_destroy(cuse_class); |
| } |
| |
| module_init(cuse_init); |
| module_exit(cuse_exit); |
| |
| MODULE_AUTHOR("Tejun Heo <tj@kernel.org>"); |
| MODULE_DESCRIPTION("Character device in Userspace"); |
| MODULE_LICENSE("GPL"); |