From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- fs/fuse/cuse.c | 655 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 655 insertions(+) create mode 100644 fs/fuse/cuse.c (limited to 'fs/fuse/cuse.c') diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c new file mode 100644 index 000000000..c7d882a9f --- /dev/null +++ b/fs/fuse/cuse.c @@ -0,0 +1,655 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * CUSE: Character device in Userspace + * + * Copyright (C) 2008-2009 SUSE Linux Products GmbH + * Copyright (C) 2008-2009 Tejun Heo + * + * 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "fuse_i.h" + +#define CUSE_CONNTBL_LEN 64 + +struct cuse_conn { + struct list_head list; /* linked on cuse_conntbl */ + struct fuse_mount fm; /* Dummy mount referencing fc */ + 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->fm, 0, file, 0); + if (rc) + fuse_conn_put(&cc->fc); + return rc; +} + +static int cuse_release(struct inode *inode, struct file *file) +{ + struct fuse_file *ff = file->private_data; + struct fuse_mount *fm = ff->fm; + + fuse_sync_release(NULL, ff, file->f_flags); + fuse_conn_put(fm->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->fm->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->fm->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 *key, *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); +} + +struct cuse_init_args { + struct fuse_args_pages ap; + struct cuse_init_in in; + struct cuse_init_out out; + struct page *page; + struct fuse_page_desc desc; +}; + +/** + * 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_mount *fm, + struct fuse_args *args, int error) +{ + struct fuse_conn *fc = fm->fc; + struct cuse_init_args *ia = container_of(args, typeof(*ia), ap.args); + struct fuse_args_pages *ap = &ia->ap; + struct cuse_conn *cc = fc_to_cc(fc), *pos; + struct cuse_init_out *arg = &ia->out; + struct page *page = ap->pages[0]; + struct cuse_devinfo devinfo = { }; + struct device *dev; + struct cdev *cdev; + dev_t devt; + int rc, i; + + if (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), ap->args.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(ia); + __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 page *page; + struct fuse_mount *fm = &cc->fm; + struct cuse_init_args *ia; + struct fuse_args_pages *ap; + + BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE); + + rc = -ENOMEM; + page = alloc_page(GFP_KERNEL | __GFP_ZERO); + if (!page) + goto err; + + ia = kzalloc(sizeof(*ia), GFP_KERNEL); + if (!ia) + goto err_free_page; + + ap = &ia->ap; + ia->in.major = FUSE_KERNEL_VERSION; + ia->in.minor = FUSE_KERNEL_MINOR_VERSION; + ia->in.flags |= CUSE_UNRESTRICTED_IOCTL; + ap->args.opcode = CUSE_INIT; + ap->args.in_numargs = 1; + ap->args.in_args[0].size = sizeof(ia->in); + ap->args.in_args[0].value = &ia->in; + ap->args.out_numargs = 2; + ap->args.out_args[0].size = sizeof(ia->out); + ap->args.out_args[0].value = &ia->out; + ap->args.out_args[1].size = CUSE_INIT_INFO_MAX; + ap->args.out_argvar = true; + ap->args.out_pages = true; + ap->num_pages = 1; + ap->pages = &ia->page; + ap->descs = &ia->desc; + ia->page = page; + ia->desc.length = ap->args.out_args[1].size; + ap->args.end = cuse_process_init_reply; + + rc = fuse_simple_background(fm, &ap->args, GFP_KERNEL); + if (rc) { + kfree(ia); +err_free_page: + __free_page(page); + } +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, &cc->fm, file->f_cred->user_ns, + &fuse_dev_fiq_ops, NULL); + + cc->fc.release = cuse_fc_release; + fud = fuse_dev_alloc_install(&cc->fc); + fuse_conn_put(&cc->fc); + if (!fud) + return -ENOMEM; + + INIT_LIST_HEAD(&cc->list); + + 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); + } + + 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 is not prepared for FUSE_DEV_IOC_CLONE */ + cuse_channel_fops.unlocked_ioctl = NULL; + + 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 "); +MODULE_DESCRIPTION("Character device in Userspace"); +MODULE_LICENSE("GPL"); -- cgit v1.2.3