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1/*
2 * CUSE: Character device in Userspace
3 *
4 * Copyright (C) 2008-2009 SUSE Linux Products GmbH
5 * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org>
6 *
7 * This file is released under the GPLv2.
8 *
9 * CUSE enables character devices to be implemented from userland much
10 * like FUSE allows filesystems. On initialization /dev/cuse is
11 * created. By opening the file and replying to the CUSE_INIT request
12 * userland CUSE server can create a character device. After that the
13 * operation is very similar to FUSE.
14 *
15 * A CUSE instance involves the following objects.
16 *
17 * cuse_conn : contains fuse_conn and serves as bonding structure
18 * channel : file handle connected to the userland CUSE server
19 * cdev : the implemented character device
20 * dev : generic device for cdev
21 *
22 * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with
23 * devices, it's called 'channel' to reduce confusion.
24 *
25 * channel determines when the character device dies. When channel is
26 * closed, everything begins to destruct. The cuse_conn is taken off
27 * the lookup table preventing further access from cdev, cdev and
28 * generic device are removed and the base reference of cuse_conn is
29 * put.
30 *
31 * On each open, the matching cuse_conn is looked up and if found an
32 * additional reference is taken which is released when the file is
33 * closed.
34 */
35
36#include <linux/fuse.h>
37#include <linux/cdev.h>
38#include <linux/device.h>
39#include <linux/file.h>
40#include <linux/fs.h>
41#include <linux/kdev_t.h>
42#include <linux/kthread.h>
43#include <linux/list.h>
44#include <linux/magic.h>
45#include <linux/miscdevice.h>
46#include <linux/mutex.h>
47#include <linux/slab.h>
48#include <linux/spinlock.h>
49#include <linux/stat.h>
50#include <linux/module.h>
51
52#include "fuse_i.h"
53
54#define CUSE_CONNTBL_LEN 64
55
56struct cuse_conn {
57 struct list_head list; /* linked on cuse_conntbl */
58 struct fuse_conn fc; /* fuse connection */
59 struct cdev *cdev; /* associated character device */
60 struct device *dev; /* device representing @cdev */
61
62 /* init parameters, set once during initialization */
63 bool unrestricted_ioctl;
64};
65
66static DEFINE_SPINLOCK(cuse_lock); /* protects cuse_conntbl */
67static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
68static struct class *cuse_class;
69
70static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
71{
72 return container_of(fc, struct cuse_conn, fc);
73}
74
75static struct list_head *cuse_conntbl_head(dev_t devt)
76{
77 return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
78}
79
80
81/**************************************************************************
82 * CUSE frontend operations
83 *
84 * These are file operations for the character device.
85 *
86 * On open, CUSE opens a file from the FUSE mnt and stores it to
87 * private_data of the open file. All other ops call FUSE ops on the
88 * FUSE file.
89 */
90
91static ssize_t cuse_read(struct file *file, char __user *buf, size_t count,
92 loff_t *ppos)
93{
94 loff_t pos = 0;
95
96 return fuse_direct_io(file, buf, count, &pos, 0);
97}
98
99static ssize_t cuse_write(struct file *file, const char __user *buf,
100 size_t count, loff_t *ppos)
101{
102 loff_t pos = 0;
103 /*
104 * No locking or generic_write_checks(), the server is
105 * responsible for locking and sanity checks.
106 */
107 return fuse_direct_io(file, buf, count, &pos, 1);
108}
109
110static int cuse_open(struct inode *inode, struct file *file)
111{
112 dev_t devt = inode->i_cdev->dev;
113 struct cuse_conn *cc = NULL, *pos;
114 int rc;
115
116 /* look up and get the connection */
117 spin_lock(&cuse_lock);
118 list_for_each_entry(pos, cuse_conntbl_head(devt), list)
119 if (pos->dev->devt == devt) {
120 fuse_conn_get(&pos->fc);
121 cc = pos;
122 break;
123 }
124 spin_unlock(&cuse_lock);
125
126 /* dead? */
127 if (!cc)
128 return -ENODEV;
129
130 /*
131 * Generic permission check is already done against the chrdev
132 * file, proceed to open.
133 */
134 rc = fuse_do_open(&cc->fc, 0, file, 0);
135 if (rc)
136 fuse_conn_put(&cc->fc);
137 return rc;
138}
139
140static int cuse_release(struct inode *inode, struct file *file)
141{
142 struct fuse_file *ff = file->private_data;
143 struct fuse_conn *fc = ff->fc;
144
145 fuse_sync_release(ff, file->f_flags);
146 fuse_conn_put(fc);
147
148 return 0;
149}
150
151static long cuse_file_ioctl(struct file *file, unsigned int cmd,
152 unsigned long arg)
153{
154 struct fuse_file *ff = file->private_data;
155 struct cuse_conn *cc = fc_to_cc(ff->fc);
156 unsigned int flags = 0;
157
158 if (cc->unrestricted_ioctl)
159 flags |= FUSE_IOCTL_UNRESTRICTED;
160
161 return fuse_do_ioctl(file, cmd, arg, flags);
162}
163
164static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
165 unsigned long arg)
166{
167 struct fuse_file *ff = file->private_data;
168 struct cuse_conn *cc = fc_to_cc(ff->fc);
169 unsigned int flags = FUSE_IOCTL_COMPAT;
170
171 if (cc->unrestricted_ioctl)
172 flags |= FUSE_IOCTL_UNRESTRICTED;
173
174 return fuse_do_ioctl(file, cmd, arg, flags);
175}
176
177static const struct file_operations cuse_frontend_fops = {
178 .owner = THIS_MODULE,
179 .read = cuse_read,
180 .write = cuse_write,
181 .open = cuse_open,
182 .release = cuse_release,
183 .unlocked_ioctl = cuse_file_ioctl,
184 .compat_ioctl = cuse_file_compat_ioctl,
185 .poll = fuse_file_poll,
186 .llseek = noop_llseek,
187};
188
189
190/**************************************************************************
191 * CUSE channel initialization and destruction
192 */
193
194struct cuse_devinfo {
195 const char *name;
196};
197
198/**
199 * cuse_parse_one - parse one key=value pair
200 * @pp: i/o parameter for the current position
201 * @end: points to one past the end of the packed string
202 * @keyp: out parameter for key
203 * @valp: out parameter for value
204 *
205 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
206 * at @end - 1. This function parses one pair and set *@keyp to the
207 * start of the key and *@valp to the start of the value. Note that
208 * the original string is modified such that the key string is
209 * terminated with '\0'. *@pp is updated to point to the next string.
210 *
211 * RETURNS:
212 * 1 on successful parse, 0 on EOF, -errno on failure.
213 */
214static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
215{
216 char *p = *pp;
217 char *key, *val;
218
219 while (p < end && *p == '\0')
220 p++;
221 if (p == end)
222 return 0;
223
224 if (end[-1] != '\0') {
225 printk(KERN_ERR "CUSE: info not properly terminated\n");
226 return -EINVAL;
227 }
228
229 key = val = p;
230 p += strlen(p);
231
232 if (valp) {
233 strsep(&val, "=");
234 if (!val)
235 val = key + strlen(key);
236 key = strstrip(key);
237 val = strstrip(val);
238 } else
239 key = strstrip(key);
240
241 if (!strlen(key)) {
242 printk(KERN_ERR "CUSE: zero length info key specified\n");
243 return -EINVAL;
244 }
245
246 *pp = p;
247 *keyp = key;
248 if (valp)
249 *valp = val;
250
251 return 1;
252}
253
254/**
255 * cuse_parse_dev_info - parse device info
256 * @p: device info string
257 * @len: length of device info string
258 * @devinfo: out parameter for parsed device info
259 *
260 * Parse @p to extract device info and store it into @devinfo. String
261 * pointed to by @p is modified by parsing and @devinfo points into
262 * them, so @p shouldn't be freed while @devinfo is in use.
263 *
264 * RETURNS:
265 * 0 on success, -errno on failure.
266 */
267static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
268{
269 char *end = p + len;
270 char *key, *val;
271 int rc;
272
273 while (true) {
274 rc = cuse_parse_one(&p, end, &key, &val);
275 if (rc < 0)
276 return rc;
277 if (!rc)
278 break;
279 if (strcmp(key, "DEVNAME") == 0)
280 devinfo->name = val;
281 else
282 printk(KERN_WARNING "CUSE: unknown device info \"%s\"\n",
283 key);
284 }
285
286 if (!devinfo->name || !strlen(devinfo->name)) {
287 printk(KERN_ERR "CUSE: DEVNAME unspecified\n");
288 return -EINVAL;
289 }
290
291 return 0;
292}
293
294static void cuse_gendev_release(struct device *dev)
295{
296 kfree(dev);
297}
298
299/**
300 * cuse_process_init_reply - finish initializing CUSE channel
301 *
302 * This function creates the character device and sets up all the
303 * required data structures for it. Please read the comment at the
304 * top of this file for high level overview.
305 */
306static void cuse_process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
307{
308 struct cuse_conn *cc = fc_to_cc(fc);
309 struct cuse_init_out *arg = req->out.args[0].value;
310 struct page *page = req->pages[0];
311 struct cuse_devinfo devinfo = { };
312 struct device *dev;
313 struct cdev *cdev;
314 dev_t devt;
315 int rc;
316
317 if (req->out.h.error ||
318 arg->major != FUSE_KERNEL_VERSION || arg->minor < 11) {
319 goto err;
320 }
321
322 fc->minor = arg->minor;
323 fc->max_read = max_t(unsigned, arg->max_read, 4096);
324 fc->max_write = max_t(unsigned, arg->max_write, 4096);
325
326 /* parse init reply */
327 cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
328
329 rc = cuse_parse_devinfo(page_address(page), req->out.args[1].size,
330 &devinfo);
331 if (rc)
332 goto err;
333
334 /* determine and reserve devt */
335 devt = MKDEV(arg->dev_major, arg->dev_minor);
336 if (!MAJOR(devt))
337 rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
338 else
339 rc = register_chrdev_region(devt, 1, devinfo.name);
340 if (rc) {
341 printk(KERN_ERR "CUSE: failed to register chrdev region\n");
342 goto err;
343 }
344
345 /* devt determined, create device */
346 rc = -ENOMEM;
347 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
348 if (!dev)
349 goto err_region;
350
351 device_initialize(dev);
352 dev_set_uevent_suppress(dev, 1);
353 dev->class = cuse_class;
354 dev->devt = devt;
355 dev->release = cuse_gendev_release;
356 dev_set_drvdata(dev, cc);
357 dev_set_name(dev, "%s", devinfo.name);
358
359 rc = device_add(dev);
360 if (rc)
361 goto err_device;
362
363 /* register cdev */
364 rc = -ENOMEM;
365 cdev = cdev_alloc();
366 if (!cdev)
367 goto err_device;
368
369 cdev->owner = THIS_MODULE;
370 cdev->ops = &cuse_frontend_fops;
371
372 rc = cdev_add(cdev, devt, 1);
373 if (rc)
374 goto err_cdev;
375
376 cc->dev = dev;
377 cc->cdev = cdev;
378
379 /* make the device available */
380 spin_lock(&cuse_lock);
381 list_add(&cc->list, cuse_conntbl_head(devt));
382 spin_unlock(&cuse_lock);
383
384 /* announce device availability */
385 dev_set_uevent_suppress(dev, 0);
386 kobject_uevent(&dev->kobj, KOBJ_ADD);
387out:
388 kfree(arg);
389 __free_page(page);
390 return;
391
392err_cdev:
393 cdev_del(cdev);
394err_device:
395 put_device(dev);
396err_region:
397 unregister_chrdev_region(devt, 1);
398err:
399 fc->conn_error = 1;
400 goto out;
401}
402
403static int cuse_send_init(struct cuse_conn *cc)
404{
405 int rc;
406 struct fuse_req *req;
407 struct page *page;
408 struct fuse_conn *fc = &cc->fc;
409 struct cuse_init_in *arg;
410 void *outarg;
411
412 BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
413
414 req = fuse_get_req(fc);
415 if (IS_ERR(req)) {
416 rc = PTR_ERR(req);
417 goto err;
418 }
419
420 rc = -ENOMEM;
421 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
422 if (!page)
423 goto err_put_req;
424
425 outarg = kzalloc(sizeof(struct cuse_init_out), GFP_KERNEL);
426 if (!outarg)
427 goto err_free_page;
428
429 arg = &req->misc.cuse_init_in;
430 arg->major = FUSE_KERNEL_VERSION;
431 arg->minor = FUSE_KERNEL_MINOR_VERSION;
432 arg->flags |= CUSE_UNRESTRICTED_IOCTL;
433 req->in.h.opcode = CUSE_INIT;
434 req->in.numargs = 1;
435 req->in.args[0].size = sizeof(struct cuse_init_in);
436 req->in.args[0].value = arg;
437 req->out.numargs = 2;
438 req->out.args[0].size = sizeof(struct cuse_init_out);
439 req->out.args[0].value = outarg;
440 req->out.args[1].size = CUSE_INIT_INFO_MAX;
441 req->out.argvar = 1;
442 req->out.argpages = 1;
443 req->pages[0] = page;
444 req->num_pages = 1;
445 req->end = cuse_process_init_reply;
446 fuse_request_send_background(fc, req);
447
448 return 0;
449
450err_free_page:
451 __free_page(page);
452err_put_req:
453 fuse_put_request(fc, req);
454err:
455 return rc;
456}
457
458static void cuse_fc_release(struct fuse_conn *fc)
459{
460 struct cuse_conn *cc = fc_to_cc(fc);
461 kfree(cc);
462}
463
464/**
465 * cuse_channel_open - open method for /dev/cuse
466 * @inode: inode for /dev/cuse
467 * @file: file struct being opened
468 *
469 * Userland CUSE server can create a CUSE device by opening /dev/cuse
470 * and replying to the initialization request kernel sends. This
471 * function is responsible for handling CUSE device initialization.
472 * Because the fd opened by this function is used during
473 * initialization, this function only creates cuse_conn and sends
474 * init. The rest is delegated to a kthread.
475 *
476 * RETURNS:
477 * 0 on success, -errno on failure.
478 */
479static int cuse_channel_open(struct inode *inode, struct file *file)
480{
481 struct cuse_conn *cc;
482 int rc;
483
484 /* set up cuse_conn */
485 cc = kzalloc(sizeof(*cc), GFP_KERNEL);
486 if (!cc)
487 return -ENOMEM;
488
489 fuse_conn_init(&cc->fc);
490
491 INIT_LIST_HEAD(&cc->list);
492 cc->fc.release = cuse_fc_release;
493
494 cc->fc.connected = 1;
495 cc->fc.blocked = 0;
496 rc = cuse_send_init(cc);
497 if (rc) {
498 fuse_conn_put(&cc->fc);
499 return rc;
500 }
501 file->private_data = &cc->fc; /* channel owns base reference to cc */
502
503 return 0;
504}
505
506/**
507 * cuse_channel_release - release method for /dev/cuse
508 * @inode: inode for /dev/cuse
509 * @file: file struct being closed
510 *
511 * Disconnect the channel, deregister CUSE device and initiate
512 * destruction by putting the default reference.
513 *
514 * RETURNS:
515 * 0 on success, -errno on failure.
516 */
517static int cuse_channel_release(struct inode *inode, struct file *file)
518{
519 struct cuse_conn *cc = fc_to_cc(file->private_data);
520 int rc;
521
522 /* remove from the conntbl, no more access from this point on */
523 spin_lock(&cuse_lock);
524 list_del_init(&cc->list);
525 spin_unlock(&cuse_lock);
526
527 /* remove device */
528 if (cc->dev)
529 device_unregister(cc->dev);
530 if (cc->cdev) {
531 unregister_chrdev_region(cc->cdev->dev, 1);
532 cdev_del(cc->cdev);
533 }
534
535 /* kill connection and shutdown channel */
536 fuse_conn_kill(&cc->fc);
537 rc = fuse_dev_release(inode, file); /* puts the base reference */
538
539 return rc;
540}
541
542static struct file_operations cuse_channel_fops; /* initialized during init */
543
544
545/**************************************************************************
546 * Misc stuff and module initializatiion
547 *
548 * CUSE exports the same set of attributes to sysfs as fusectl.
549 */
550
551static ssize_t cuse_class_waiting_show(struct device *dev,
552 struct device_attribute *attr, char *buf)
553{
554 struct cuse_conn *cc = dev_get_drvdata(dev);
555
556 return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
557}
558
559static ssize_t cuse_class_abort_store(struct device *dev,
560 struct device_attribute *attr,
561 const char *buf, size_t count)
562{
563 struct cuse_conn *cc = dev_get_drvdata(dev);
564
565 fuse_abort_conn(&cc->fc);
566 return count;
567}
568
569static struct device_attribute cuse_class_dev_attrs[] = {
570 __ATTR(waiting, S_IFREG | 0400, cuse_class_waiting_show, NULL),
571 __ATTR(abort, S_IFREG | 0200, NULL, cuse_class_abort_store),
572 { }
573};
574
575static struct miscdevice cuse_miscdev = {
576 .minor = MISC_DYNAMIC_MINOR,
577 .name = "cuse",
578 .fops = &cuse_channel_fops,
579};
580
581static int __init cuse_init(void)
582{
583 int i, rc;
584
585 /* init conntbl */
586 for (i = 0; i < CUSE_CONNTBL_LEN; i++)
587 INIT_LIST_HEAD(&cuse_conntbl[i]);
588
589 /* inherit and extend fuse_dev_operations */
590 cuse_channel_fops = fuse_dev_operations;
591 cuse_channel_fops.owner = THIS_MODULE;
592 cuse_channel_fops.open = cuse_channel_open;
593 cuse_channel_fops.release = cuse_channel_release;
594
595 cuse_class = class_create(THIS_MODULE, "cuse");
596 if (IS_ERR(cuse_class))
597 return PTR_ERR(cuse_class);
598
599 cuse_class->dev_attrs = cuse_class_dev_attrs;
600
601 rc = misc_register(&cuse_miscdev);
602 if (rc) {
603 class_destroy(cuse_class);
604 return rc;
605 }
606
607 return 0;
608}
609
610static void __exit cuse_exit(void)
611{
612 misc_deregister(&cuse_miscdev);
613 class_destroy(cuse_class);
614}
615
616module_init(cuse_init);
617module_exit(cuse_exit);
618
619MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
620MODULE_DESCRIPTION("Character device in Userspace");
621MODULE_LICENSE("GPL");
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * CUSE: Character device in Userspace
4 *
5 * Copyright (C) 2008-2009 SUSE Linux Products GmbH
6 * Copyright (C) 2008-2009 Tejun Heo <tj@kernel.org>
7 *
8 * CUSE enables character devices to be implemented from userland much
9 * like FUSE allows filesystems. On initialization /dev/cuse is
10 * created. By opening the file and replying to the CUSE_INIT request
11 * userland CUSE server can create a character device. After that the
12 * operation is very similar to FUSE.
13 *
14 * A CUSE instance involves the following objects.
15 *
16 * cuse_conn : contains fuse_conn and serves as bonding structure
17 * channel : file handle connected to the userland CUSE server
18 * cdev : the implemented character device
19 * dev : generic device for cdev
20 *
21 * Note that 'channel' is what 'dev' is in FUSE. As CUSE deals with
22 * devices, it's called 'channel' to reduce confusion.
23 *
24 * channel determines when the character device dies. When channel is
25 * closed, everything begins to destruct. The cuse_conn is taken off
26 * the lookup table preventing further access from cdev, cdev and
27 * generic device are removed and the base reference of cuse_conn is
28 * put.
29 *
30 * On each open, the matching cuse_conn is looked up and if found an
31 * additional reference is taken which is released when the file is
32 * closed.
33 */
34
35#define pr_fmt(fmt) "CUSE: " fmt
36
37#include <linux/fuse.h>
38#include <linux/cdev.h>
39#include <linux/device.h>
40#include <linux/file.h>
41#include <linux/fs.h>
42#include <linux/kdev_t.h>
43#include <linux/kthread.h>
44#include <linux/list.h>
45#include <linux/magic.h>
46#include <linux/miscdevice.h>
47#include <linux/mutex.h>
48#include <linux/slab.h>
49#include <linux/stat.h>
50#include <linux/module.h>
51#include <linux/uio.h>
52#include <linux/user_namespace.h>
53
54#include "fuse_i.h"
55
56#define CUSE_CONNTBL_LEN 64
57
58struct cuse_conn {
59 struct list_head list; /* linked on cuse_conntbl */
60 struct fuse_mount fm; /* Dummy mount referencing fc */
61 struct fuse_conn fc; /* fuse connection */
62 struct cdev *cdev; /* associated character device */
63 struct device *dev; /* device representing @cdev */
64
65 /* init parameters, set once during initialization */
66 bool unrestricted_ioctl;
67};
68
69static DEFINE_MUTEX(cuse_lock); /* protects registration */
70static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
71static struct class *cuse_class;
72
73static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
74{
75 return container_of(fc, struct cuse_conn, fc);
76}
77
78static struct list_head *cuse_conntbl_head(dev_t devt)
79{
80 return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
81}
82
83
84/**************************************************************************
85 * CUSE frontend operations
86 *
87 * These are file operations for the character device.
88 *
89 * On open, CUSE opens a file from the FUSE mnt and stores it to
90 * private_data of the open file. All other ops call FUSE ops on the
91 * FUSE file.
92 */
93
94static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
95{
96 struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb);
97 loff_t pos = 0;
98
99 return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE);
100}
101
102static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from)
103{
104 struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb);
105 loff_t pos = 0;
106 /*
107 * No locking or generic_write_checks(), the server is
108 * responsible for locking and sanity checks.
109 */
110 return fuse_direct_io(&io, from, &pos,
111 FUSE_DIO_WRITE | FUSE_DIO_CUSE);
112}
113
114static int cuse_open(struct inode *inode, struct file *file)
115{
116 dev_t devt = inode->i_cdev->dev;
117 struct cuse_conn *cc = NULL, *pos;
118 int rc;
119
120 /* look up and get the connection */
121 mutex_lock(&cuse_lock);
122 list_for_each_entry(pos, cuse_conntbl_head(devt), list)
123 if (pos->dev->devt == devt) {
124 fuse_conn_get(&pos->fc);
125 cc = pos;
126 break;
127 }
128 mutex_unlock(&cuse_lock);
129
130 /* dead? */
131 if (!cc)
132 return -ENODEV;
133
134 /*
135 * Generic permission check is already done against the chrdev
136 * file, proceed to open.
137 */
138 rc = fuse_do_open(&cc->fm, 0, file, 0);
139 if (rc)
140 fuse_conn_put(&cc->fc);
141 return rc;
142}
143
144static int cuse_release(struct inode *inode, struct file *file)
145{
146 struct fuse_file *ff = file->private_data;
147 struct fuse_mount *fm = ff->fm;
148
149 fuse_sync_release(NULL, ff, file->f_flags);
150 fuse_conn_put(fm->fc);
151
152 return 0;
153}
154
155static long cuse_file_ioctl(struct file *file, unsigned int cmd,
156 unsigned long arg)
157{
158 struct fuse_file *ff = file->private_data;
159 struct cuse_conn *cc = fc_to_cc(ff->fm->fc);
160 unsigned int flags = 0;
161
162 if (cc->unrestricted_ioctl)
163 flags |= FUSE_IOCTL_UNRESTRICTED;
164
165 return fuse_do_ioctl(file, cmd, arg, flags);
166}
167
168static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
169 unsigned long arg)
170{
171 struct fuse_file *ff = file->private_data;
172 struct cuse_conn *cc = fc_to_cc(ff->fm->fc);
173 unsigned int flags = FUSE_IOCTL_COMPAT;
174
175 if (cc->unrestricted_ioctl)
176 flags |= FUSE_IOCTL_UNRESTRICTED;
177
178 return fuse_do_ioctl(file, cmd, arg, flags);
179}
180
181static const struct file_operations cuse_frontend_fops = {
182 .owner = THIS_MODULE,
183 .read_iter = cuse_read_iter,
184 .write_iter = cuse_write_iter,
185 .open = cuse_open,
186 .release = cuse_release,
187 .unlocked_ioctl = cuse_file_ioctl,
188 .compat_ioctl = cuse_file_compat_ioctl,
189 .poll = fuse_file_poll,
190 .llseek = noop_llseek,
191};
192
193
194/**************************************************************************
195 * CUSE channel initialization and destruction
196 */
197
198struct cuse_devinfo {
199 const char *name;
200};
201
202/**
203 * cuse_parse_one - parse one key=value pair
204 * @pp: i/o parameter for the current position
205 * @end: points to one past the end of the packed string
206 * @keyp: out parameter for key
207 * @valp: out parameter for value
208 *
209 * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
210 * at @end - 1. This function parses one pair and set *@keyp to the
211 * start of the key and *@valp to the start of the value. Note that
212 * the original string is modified such that the key string is
213 * terminated with '\0'. *@pp is updated to point to the next string.
214 *
215 * RETURNS:
216 * 1 on successful parse, 0 on EOF, -errno on failure.
217 */
218static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
219{
220 char *p = *pp;
221 char *key, *val;
222
223 while (p < end && *p == '\0')
224 p++;
225 if (p == end)
226 return 0;
227
228 if (end[-1] != '\0') {
229 pr_err("info not properly terminated\n");
230 return -EINVAL;
231 }
232
233 key = val = p;
234 p += strlen(p);
235
236 if (valp) {
237 strsep(&val, "=");
238 if (!val)
239 val = key + strlen(key);
240 key = strstrip(key);
241 val = strstrip(val);
242 } else
243 key = strstrip(key);
244
245 if (!strlen(key)) {
246 pr_err("zero length info key specified\n");
247 return -EINVAL;
248 }
249
250 *pp = p;
251 *keyp = key;
252 if (valp)
253 *valp = val;
254
255 return 1;
256}
257
258/**
259 * cuse_parse_devinfo - parse device info
260 * @p: device info string
261 * @len: length of device info string
262 * @devinfo: out parameter for parsed device info
263 *
264 * Parse @p to extract device info and store it into @devinfo. String
265 * pointed to by @p is modified by parsing and @devinfo points into
266 * them, so @p shouldn't be freed while @devinfo is in use.
267 *
268 * RETURNS:
269 * 0 on success, -errno on failure.
270 */
271static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
272{
273 char *end = p + len;
274 char *key, *val;
275 int rc;
276
277 while (true) {
278 rc = cuse_parse_one(&p, end, &key, &val);
279 if (rc < 0)
280 return rc;
281 if (!rc)
282 break;
283 if (strcmp(key, "DEVNAME") == 0)
284 devinfo->name = val;
285 else
286 pr_warn("unknown device info \"%s\"\n", key);
287 }
288
289 if (!devinfo->name || !strlen(devinfo->name)) {
290 pr_err("DEVNAME unspecified\n");
291 return -EINVAL;
292 }
293
294 return 0;
295}
296
297static void cuse_gendev_release(struct device *dev)
298{
299 kfree(dev);
300}
301
302struct cuse_init_args {
303 struct fuse_args_pages ap;
304 struct cuse_init_in in;
305 struct cuse_init_out out;
306 struct folio *folio;
307 struct fuse_folio_desc desc;
308};
309
310/**
311 * cuse_process_init_reply - finish initializing CUSE channel
312 *
313 * @fm: The fuse mount information containing the CUSE connection.
314 * @args: The arguments passed to the init reply.
315 * @error: The error code signifying if any error occurred during the process.
316 *
317 * This function creates the character device and sets up all the
318 * required data structures for it. Please read the comment at the
319 * top of this file for high level overview.
320 */
321static void cuse_process_init_reply(struct fuse_mount *fm,
322 struct fuse_args *args, int error)
323{
324 struct fuse_conn *fc = fm->fc;
325 struct cuse_init_args *ia = container_of(args, typeof(*ia), ap.args);
326 struct fuse_args_pages *ap = &ia->ap;
327 struct cuse_conn *cc = fc_to_cc(fc), *pos;
328 struct cuse_init_out *arg = &ia->out;
329 struct folio *folio = ap->folios[0];
330 struct cuse_devinfo devinfo = { };
331 struct device *dev;
332 struct cdev *cdev;
333 dev_t devt;
334 int rc, i;
335
336 if (error || arg->major != FUSE_KERNEL_VERSION || arg->minor < 11)
337 goto err;
338
339 fc->minor = arg->minor;
340 fc->max_read = max_t(unsigned, arg->max_read, 4096);
341 fc->max_write = max_t(unsigned, arg->max_write, 4096);
342
343 /* parse init reply */
344 cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
345
346 rc = cuse_parse_devinfo(folio_address(folio), ap->args.out_args[1].size,
347 &devinfo);
348 if (rc)
349 goto err;
350
351 /* determine and reserve devt */
352 devt = MKDEV(arg->dev_major, arg->dev_minor);
353 if (!MAJOR(devt))
354 rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
355 else
356 rc = register_chrdev_region(devt, 1, devinfo.name);
357 if (rc) {
358 pr_err("failed to register chrdev region\n");
359 goto err;
360 }
361
362 /* devt determined, create device */
363 rc = -ENOMEM;
364 dev = kzalloc(sizeof(*dev), GFP_KERNEL);
365 if (!dev)
366 goto err_region;
367
368 device_initialize(dev);
369 dev_set_uevent_suppress(dev, 1);
370 dev->class = cuse_class;
371 dev->devt = devt;
372 dev->release = cuse_gendev_release;
373 dev_set_drvdata(dev, cc);
374 dev_set_name(dev, "%s", devinfo.name);
375
376 mutex_lock(&cuse_lock);
377
378 /* make sure the device-name is unique */
379 for (i = 0; i < CUSE_CONNTBL_LEN; ++i) {
380 list_for_each_entry(pos, &cuse_conntbl[i], list)
381 if (!strcmp(dev_name(pos->dev), dev_name(dev)))
382 goto err_unlock;
383 }
384
385 rc = device_add(dev);
386 if (rc)
387 goto err_unlock;
388
389 /* register cdev */
390 rc = -ENOMEM;
391 cdev = cdev_alloc();
392 if (!cdev)
393 goto err_unlock;
394
395 cdev->owner = THIS_MODULE;
396 cdev->ops = &cuse_frontend_fops;
397
398 rc = cdev_add(cdev, devt, 1);
399 if (rc)
400 goto err_cdev;
401
402 cc->dev = dev;
403 cc->cdev = cdev;
404
405 /* make the device available */
406 list_add(&cc->list, cuse_conntbl_head(devt));
407 mutex_unlock(&cuse_lock);
408
409 /* announce device availability */
410 dev_set_uevent_suppress(dev, 0);
411 kobject_uevent(&dev->kobj, KOBJ_ADD);
412out:
413 kfree(ia);
414 folio_put(folio);
415 return;
416
417err_cdev:
418 cdev_del(cdev);
419err_unlock:
420 mutex_unlock(&cuse_lock);
421 put_device(dev);
422err_region:
423 unregister_chrdev_region(devt, 1);
424err:
425 fuse_abort_conn(fc);
426 goto out;
427}
428
429static int cuse_send_init(struct cuse_conn *cc)
430{
431 int rc;
432 struct folio *folio;
433 struct fuse_mount *fm = &cc->fm;
434 struct cuse_init_args *ia;
435 struct fuse_args_pages *ap;
436
437 BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
438
439 rc = -ENOMEM;
440
441 folio = folio_alloc(GFP_KERNEL | __GFP_ZERO, 0);
442 if (!folio)
443 goto err;
444
445 ia = kzalloc(sizeof(*ia), GFP_KERNEL);
446 if (!ia)
447 goto err_free_folio;
448
449 ap = &ia->ap;
450 ia->in.major = FUSE_KERNEL_VERSION;
451 ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
452 ia->in.flags |= CUSE_UNRESTRICTED_IOCTL;
453 ap->args.opcode = CUSE_INIT;
454 ap->args.in_numargs = 1;
455 ap->args.in_args[0].size = sizeof(ia->in);
456 ap->args.in_args[0].value = &ia->in;
457 ap->args.out_numargs = 2;
458 ap->args.out_args[0].size = sizeof(ia->out);
459 ap->args.out_args[0].value = &ia->out;
460 ap->args.out_args[1].size = CUSE_INIT_INFO_MAX;
461 ap->args.out_argvar = true;
462 ap->args.out_pages = true;
463 ap->num_folios = 1;
464 ap->folios = &ia->folio;
465 ap->descs = &ia->desc;
466 ia->folio = folio;
467 ia->desc.length = ap->args.out_args[1].size;
468 ap->args.end = cuse_process_init_reply;
469
470 rc = fuse_simple_background(fm, &ap->args, GFP_KERNEL);
471 if (rc) {
472 kfree(ia);
473err_free_folio:
474 folio_put(folio);
475 }
476err:
477 return rc;
478}
479
480static void cuse_fc_release(struct fuse_conn *fc)
481{
482 kfree(fc_to_cc(fc));
483}
484
485/**
486 * cuse_channel_open - open method for /dev/cuse
487 * @inode: inode for /dev/cuse
488 * @file: file struct being opened
489 *
490 * Userland CUSE server can create a CUSE device by opening /dev/cuse
491 * and replying to the initialization request kernel sends. This
492 * function is responsible for handling CUSE device initialization.
493 * Because the fd opened by this function is used during
494 * initialization, this function only creates cuse_conn and sends
495 * init. The rest is delegated to a kthread.
496 *
497 * RETURNS:
498 * 0 on success, -errno on failure.
499 */
500static int cuse_channel_open(struct inode *inode, struct file *file)
501{
502 struct fuse_dev *fud;
503 struct cuse_conn *cc;
504 int rc;
505
506 /* set up cuse_conn */
507 cc = kzalloc(sizeof(*cc), GFP_KERNEL);
508 if (!cc)
509 return -ENOMEM;
510
511 /*
512 * Limit the cuse channel to requests that can
513 * be represented in file->f_cred->user_ns.
514 */
515 fuse_conn_init(&cc->fc, &cc->fm, file->f_cred->user_ns,
516 &fuse_dev_fiq_ops, NULL);
517
518 cc->fc.release = cuse_fc_release;
519 fud = fuse_dev_alloc_install(&cc->fc);
520 fuse_conn_put(&cc->fc);
521 if (!fud)
522 return -ENOMEM;
523
524 INIT_LIST_HEAD(&cc->list);
525
526 cc->fc.initialized = 1;
527 rc = cuse_send_init(cc);
528 if (rc) {
529 fuse_dev_free(fud);
530 return rc;
531 }
532 file->private_data = fud;
533
534 return 0;
535}
536
537/**
538 * cuse_channel_release - release method for /dev/cuse
539 * @inode: inode for /dev/cuse
540 * @file: file struct being closed
541 *
542 * Disconnect the channel, deregister CUSE device and initiate
543 * destruction by putting the default reference.
544 *
545 * RETURNS:
546 * 0 on success, -errno on failure.
547 */
548static int cuse_channel_release(struct inode *inode, struct file *file)
549{
550 struct fuse_dev *fud = file->private_data;
551 struct cuse_conn *cc = fc_to_cc(fud->fc);
552
553 /* remove from the conntbl, no more access from this point on */
554 mutex_lock(&cuse_lock);
555 list_del_init(&cc->list);
556 mutex_unlock(&cuse_lock);
557
558 /* remove device */
559 if (cc->dev)
560 device_unregister(cc->dev);
561 if (cc->cdev) {
562 unregister_chrdev_region(cc->cdev->dev, 1);
563 cdev_del(cc->cdev);
564 }
565
566 return fuse_dev_release(inode, file);
567}
568
569static struct file_operations cuse_channel_fops; /* initialized during init */
570
571
572/**************************************************************************
573 * Misc stuff and module initializatiion
574 *
575 * CUSE exports the same set of attributes to sysfs as fusectl.
576 */
577
578static ssize_t cuse_class_waiting_show(struct device *dev,
579 struct device_attribute *attr, char *buf)
580{
581 struct cuse_conn *cc = dev_get_drvdata(dev);
582
583 return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
584}
585static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL);
586
587static ssize_t cuse_class_abort_store(struct device *dev,
588 struct device_attribute *attr,
589 const char *buf, size_t count)
590{
591 struct cuse_conn *cc = dev_get_drvdata(dev);
592
593 fuse_abort_conn(&cc->fc);
594 return count;
595}
596static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);
597
598static struct attribute *cuse_class_dev_attrs[] = {
599 &dev_attr_waiting.attr,
600 &dev_attr_abort.attr,
601 NULL,
602};
603ATTRIBUTE_GROUPS(cuse_class_dev);
604
605static struct miscdevice cuse_miscdev = {
606 .minor = CUSE_MINOR,
607 .name = "cuse",
608 .fops = &cuse_channel_fops,
609};
610
611MODULE_ALIAS_MISCDEV(CUSE_MINOR);
612MODULE_ALIAS("devname:cuse");
613
614static int __init cuse_init(void)
615{
616 int i, rc;
617
618 /* init conntbl */
619 for (i = 0; i < CUSE_CONNTBL_LEN; i++)
620 INIT_LIST_HEAD(&cuse_conntbl[i]);
621
622 /* inherit and extend fuse_dev_operations */
623 cuse_channel_fops = fuse_dev_operations;
624 cuse_channel_fops.owner = THIS_MODULE;
625 cuse_channel_fops.open = cuse_channel_open;
626 cuse_channel_fops.release = cuse_channel_release;
627 /* CUSE is not prepared for FUSE_DEV_IOC_CLONE */
628 cuse_channel_fops.unlocked_ioctl = NULL;
629
630 cuse_class = class_create("cuse");
631 if (IS_ERR(cuse_class))
632 return PTR_ERR(cuse_class);
633
634 cuse_class->dev_groups = cuse_class_dev_groups;
635
636 rc = misc_register(&cuse_miscdev);
637 if (rc) {
638 class_destroy(cuse_class);
639 return rc;
640 }
641
642 return 0;
643}
644
645static void __exit cuse_exit(void)
646{
647 misc_deregister(&cuse_miscdev);
648 class_destroy(cuse_class);
649}
650
651module_init(cuse_init);
652module_exit(cuse_exit);
653
654MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
655MODULE_DESCRIPTION("Character device in Userspace");
656MODULE_LICENSE("GPL");