1 // SPDX-License-Identifier: MIT
2 /*
3  * VirtualBox Guest Shared Folders support: Virtual File System.
4  *
5  * Module initialization/finalization
6  * File system registration/deregistration
7  * Superblock reading
8  * Few utility functions
9  *
10  * Copyright (C) 2006-2018 Oracle Corporation
11  */
12 
13 #include <linux/idr.h>
14 #include <linux/fs_parser.h>
15 #include <linux/magic.h>
16 #include <linux/module.h>
17 #include <linux/nls.h>
18 #include <linux/statfs.h>
19 #include <linux/vbox_utils.h>
20 #include "vfsmod.h"
21 
22 #define VBOXSF_SUPER_MAGIC 0x786f4256 /* 'VBox' little endian */
23 
24 static const unsigned char VBSF_MOUNT_SIGNATURE[4] = "\000\377\376\375";
25 
26 static int follow_symlinks;
27 module_param(follow_symlinks, int, 0444);
28 MODULE_PARM_DESC(follow_symlinks,
29 		 "Let host resolve symlinks rather than showing them");
30 
31 static DEFINE_IDA(vboxsf_bdi_ida);
32 static DEFINE_MUTEX(vboxsf_setup_mutex);
33 static bool vboxsf_setup_done;
34 static struct super_operations vboxsf_super_ops; /* forward declaration */
35 static struct kmem_cache *vboxsf_inode_cachep;
36 
37 static char * const vboxsf_default_nls = CONFIG_NLS_DEFAULT;
38 
39 enum  { opt_nls, opt_uid, opt_gid, opt_ttl, opt_dmode, opt_fmode,
40 	opt_dmask, opt_fmask };
41 
42 static const struct fs_parameter_spec vboxsf_fs_parameters[] = {
43 	fsparam_string	("nls",		opt_nls),
44 	fsparam_u32	("uid",		opt_uid),
45 	fsparam_u32	("gid",		opt_gid),
46 	fsparam_u32	("ttl",		opt_ttl),
47 	fsparam_u32oct	("dmode",	opt_dmode),
48 	fsparam_u32oct	("fmode",	opt_fmode),
49 	fsparam_u32oct	("dmask",	opt_dmask),
50 	fsparam_u32oct	("fmask",	opt_fmask),
51 	{}
52 };
53 
vboxsf_parse_param(struct fs_context * fc,struct fs_parameter * param)54 static int vboxsf_parse_param(struct fs_context *fc, struct fs_parameter *param)
55 {
56 	struct vboxsf_fs_context *ctx = fc->fs_private;
57 	struct fs_parse_result result;
58 	kuid_t uid;
59 	kgid_t gid;
60 	int opt;
61 
62 	opt = fs_parse(fc, vboxsf_fs_parameters, param, &result);
63 	if (opt < 0)
64 		return opt;
65 
66 	switch (opt) {
67 	case opt_nls:
68 		if (ctx->nls_name || fc->purpose != FS_CONTEXT_FOR_MOUNT) {
69 			vbg_err("vboxsf: Cannot reconfigure nls option\n");
70 			return -EINVAL;
71 		}
72 		ctx->nls_name = param->string;
73 		param->string = NULL;
74 		break;
75 	case opt_uid:
76 		uid = make_kuid(current_user_ns(), result.uint_32);
77 		if (!uid_valid(uid))
78 			return -EINVAL;
79 		ctx->o.uid = uid;
80 		break;
81 	case opt_gid:
82 		gid = make_kgid(current_user_ns(), result.uint_32);
83 		if (!gid_valid(gid))
84 			return -EINVAL;
85 		ctx->o.gid = gid;
86 		break;
87 	case opt_ttl:
88 		ctx->o.ttl = msecs_to_jiffies(result.uint_32);
89 		break;
90 	case opt_dmode:
91 		if (result.uint_32 & ~0777)
92 			return -EINVAL;
93 		ctx->o.dmode = result.uint_32;
94 		ctx->o.dmode_set = true;
95 		break;
96 	case opt_fmode:
97 		if (result.uint_32 & ~0777)
98 			return -EINVAL;
99 		ctx->o.fmode = result.uint_32;
100 		ctx->o.fmode_set = true;
101 		break;
102 	case opt_dmask:
103 		if (result.uint_32 & ~07777)
104 			return -EINVAL;
105 		ctx->o.dmask = result.uint_32;
106 		break;
107 	case opt_fmask:
108 		if (result.uint_32 & ~07777)
109 			return -EINVAL;
110 		ctx->o.fmask = result.uint_32;
111 		break;
112 	default:
113 		return -EINVAL;
114 	}
115 
116 	return 0;
117 }
118 
vboxsf_fill_super(struct super_block * sb,struct fs_context * fc)119 static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
120 {
121 	struct vboxsf_fs_context *ctx = fc->fs_private;
122 	struct shfl_string *folder_name, root_path;
123 	struct vboxsf_sbi *sbi;
124 	struct dentry *droot;
125 	struct inode *iroot;
126 	char *nls_name;
127 	size_t size;
128 	int err;
129 
130 	if (!fc->source)
131 		return -EINVAL;
132 
133 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
134 	if (!sbi)
135 		return -ENOMEM;
136 
137 	sbi->o = ctx->o;
138 	idr_init(&sbi->ino_idr);
139 	spin_lock_init(&sbi->ino_idr_lock);
140 	sbi->next_generation = 1;
141 	sbi->bdi_id = -1;
142 
143 	/* Load nls if not utf8 */
144 	nls_name = ctx->nls_name ? ctx->nls_name : vboxsf_default_nls;
145 	if (strcmp(nls_name, "utf8") != 0) {
146 		if (nls_name == vboxsf_default_nls)
147 			sbi->nls = load_nls_default();
148 		else
149 			sbi->nls = load_nls(nls_name);
150 
151 		if (!sbi->nls) {
152 			vbg_err("vboxsf: Count not load '%s' nls\n", nls_name);
153 			err = -EINVAL;
154 			goto fail_free;
155 		}
156 	}
157 
158 	sbi->bdi_id = ida_simple_get(&vboxsf_bdi_ida, 0, 0, GFP_KERNEL);
159 	if (sbi->bdi_id < 0) {
160 		err = sbi->bdi_id;
161 		goto fail_free;
162 	}
163 
164 	err = super_setup_bdi_name(sb, "vboxsf-%d", sbi->bdi_id);
165 	if (err)
166 		goto fail_free;
167 	sb->s_bdi->ra_pages = 0;
168 	sb->s_bdi->io_pages = 0;
169 
170 	/* Turn source into a shfl_string and map the folder */
171 	size = strlen(fc->source) + 1;
172 	folder_name = kmalloc(SHFLSTRING_HEADER_SIZE + size, GFP_KERNEL);
173 	if (!folder_name) {
174 		err = -ENOMEM;
175 		goto fail_free;
176 	}
177 	folder_name->size = size;
178 	folder_name->length = size - 1;
179 	strlcpy(folder_name->string.utf8, fc->source, size);
180 	err = vboxsf_map_folder(folder_name, &sbi->root);
181 	kfree(folder_name);
182 	if (err) {
183 		vbg_err("vboxsf: Host rejected mount of '%s' with error %d\n",
184 			fc->source, err);
185 		goto fail_free;
186 	}
187 
188 	root_path.length = 1;
189 	root_path.size = 2;
190 	root_path.string.utf8[0] = '/';
191 	root_path.string.utf8[1] = 0;
192 	err = vboxsf_stat(sbi, &root_path, &sbi->root_info);
193 	if (err)
194 		goto fail_unmap;
195 
196 	sb->s_magic = VBOXSF_SUPER_MAGIC;
197 	sb->s_blocksize = 1024;
198 	sb->s_maxbytes = MAX_LFS_FILESIZE;
199 	sb->s_op = &vboxsf_super_ops;
200 	sb->s_d_op = &vboxsf_dentry_ops;
201 
202 	iroot = iget_locked(sb, 0);
203 	if (!iroot) {
204 		err = -ENOMEM;
205 		goto fail_unmap;
206 	}
207 	vboxsf_init_inode(sbi, iroot, &sbi->root_info, false);
208 	unlock_new_inode(iroot);
209 
210 	droot = d_make_root(iroot);
211 	if (!droot) {
212 		err = -ENOMEM;
213 		goto fail_unmap;
214 	}
215 
216 	sb->s_root = droot;
217 	sb->s_fs_info = sbi;
218 	return 0;
219 
220 fail_unmap:
221 	vboxsf_unmap_folder(sbi->root);
222 fail_free:
223 	if (sbi->bdi_id >= 0)
224 		ida_simple_remove(&vboxsf_bdi_ida, sbi->bdi_id);
225 	if (sbi->nls)
226 		unload_nls(sbi->nls);
227 	idr_destroy(&sbi->ino_idr);
228 	kfree(sbi);
229 	return err;
230 }
231 
vboxsf_inode_init_once(void * data)232 static void vboxsf_inode_init_once(void *data)
233 {
234 	struct vboxsf_inode *sf_i = data;
235 
236 	mutex_init(&sf_i->handle_list_mutex);
237 	inode_init_once(&sf_i->vfs_inode);
238 }
239 
vboxsf_alloc_inode(struct super_block * sb)240 static struct inode *vboxsf_alloc_inode(struct super_block *sb)
241 {
242 	struct vboxsf_inode *sf_i;
243 
244 	sf_i = alloc_inode_sb(sb, vboxsf_inode_cachep, GFP_NOFS);
245 	if (!sf_i)
246 		return NULL;
247 
248 	sf_i->force_restat = 0;
249 	INIT_LIST_HEAD(&sf_i->handle_list);
250 
251 	return &sf_i->vfs_inode;
252 }
253 
vboxsf_free_inode(struct inode * inode)254 static void vboxsf_free_inode(struct inode *inode)
255 {
256 	struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
257 	unsigned long flags;
258 
259 	spin_lock_irqsave(&sbi->ino_idr_lock, flags);
260 	idr_remove(&sbi->ino_idr, inode->i_ino);
261 	spin_unlock_irqrestore(&sbi->ino_idr_lock, flags);
262 	kmem_cache_free(vboxsf_inode_cachep, VBOXSF_I(inode));
263 }
264 
vboxsf_put_super(struct super_block * sb)265 static void vboxsf_put_super(struct super_block *sb)
266 {
267 	struct vboxsf_sbi *sbi = VBOXSF_SBI(sb);
268 
269 	vboxsf_unmap_folder(sbi->root);
270 	if (sbi->bdi_id >= 0)
271 		ida_simple_remove(&vboxsf_bdi_ida, sbi->bdi_id);
272 	if (sbi->nls)
273 		unload_nls(sbi->nls);
274 
275 	/*
276 	 * vboxsf_free_inode uses the idr, make sure all delayed rcu free
277 	 * inodes are flushed.
278 	 */
279 	rcu_barrier();
280 	idr_destroy(&sbi->ino_idr);
281 	kfree(sbi);
282 }
283 
vboxsf_statfs(struct dentry * dentry,struct kstatfs * stat)284 static int vboxsf_statfs(struct dentry *dentry, struct kstatfs *stat)
285 {
286 	struct super_block *sb = dentry->d_sb;
287 	struct shfl_volinfo shfl_volinfo;
288 	struct vboxsf_sbi *sbi;
289 	u32 buf_len;
290 	int err;
291 
292 	sbi = VBOXSF_SBI(sb);
293 	buf_len = sizeof(shfl_volinfo);
294 	err = vboxsf_fsinfo(sbi->root, 0, SHFL_INFO_GET | SHFL_INFO_VOLUME,
295 			    &buf_len, &shfl_volinfo);
296 	if (err)
297 		return err;
298 
299 	stat->f_type = VBOXSF_SUPER_MAGIC;
300 	stat->f_bsize = shfl_volinfo.bytes_per_allocation_unit;
301 
302 	do_div(shfl_volinfo.total_allocation_bytes,
303 	       shfl_volinfo.bytes_per_allocation_unit);
304 	stat->f_blocks = shfl_volinfo.total_allocation_bytes;
305 
306 	do_div(shfl_volinfo.available_allocation_bytes,
307 	       shfl_volinfo.bytes_per_allocation_unit);
308 	stat->f_bfree  = shfl_volinfo.available_allocation_bytes;
309 	stat->f_bavail = shfl_volinfo.available_allocation_bytes;
310 
311 	stat->f_files = 1000;
312 	/*
313 	 * Don't return 0 here since the guest may then think that it is not
314 	 * possible to create any more files.
315 	 */
316 	stat->f_ffree = 1000000;
317 	stat->f_fsid.val[0] = 0;
318 	stat->f_fsid.val[1] = 0;
319 	stat->f_namelen = 255;
320 	return 0;
321 }
322 
323 static struct super_operations vboxsf_super_ops = {
324 	.alloc_inode	= vboxsf_alloc_inode,
325 	.free_inode	= vboxsf_free_inode,
326 	.put_super	= vboxsf_put_super,
327 	.statfs		= vboxsf_statfs,
328 };
329 
vboxsf_setup(void)330 static int vboxsf_setup(void)
331 {
332 	int err;
333 
334 	mutex_lock(&vboxsf_setup_mutex);
335 
336 	if (vboxsf_setup_done)
337 		goto success;
338 
339 	vboxsf_inode_cachep =
340 		kmem_cache_create("vboxsf_inode_cache",
341 				  sizeof(struct vboxsf_inode), 0,
342 				  (SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
343 				   SLAB_ACCOUNT),
344 				  vboxsf_inode_init_once);
345 	if (!vboxsf_inode_cachep) {
346 		err = -ENOMEM;
347 		goto fail_nomem;
348 	}
349 
350 	err = vboxsf_connect();
351 	if (err) {
352 		vbg_err("vboxsf: err %d connecting to guest PCI-device\n", err);
353 		vbg_err("vboxsf: make sure you are inside a VirtualBox VM\n");
354 		vbg_err("vboxsf: and check dmesg for vboxguest errors\n");
355 		goto fail_free_cache;
356 	}
357 
358 	err = vboxsf_set_utf8();
359 	if (err) {
360 		vbg_err("vboxsf_setutf8 error %d\n", err);
361 		goto fail_disconnect;
362 	}
363 
364 	if (!follow_symlinks) {
365 		err = vboxsf_set_symlinks();
366 		if (err)
367 			vbg_warn("vboxsf: Unable to show symlinks: %d\n", err);
368 	}
369 
370 	vboxsf_setup_done = true;
371 success:
372 	mutex_unlock(&vboxsf_setup_mutex);
373 	return 0;
374 
375 fail_disconnect:
376 	vboxsf_disconnect();
377 fail_free_cache:
378 	kmem_cache_destroy(vboxsf_inode_cachep);
379 fail_nomem:
380 	mutex_unlock(&vboxsf_setup_mutex);
381 	return err;
382 }
383 
vboxsf_parse_monolithic(struct fs_context * fc,void * data)384 static int vboxsf_parse_monolithic(struct fs_context *fc, void *data)
385 {
386 	if (data && !memcmp(data, VBSF_MOUNT_SIGNATURE, 4)) {
387 		vbg_err("vboxsf: Old binary mount data not supported, remove obsolete mount.vboxsf and/or update your VBoxService.\n");
388 		return -EINVAL;
389 	}
390 
391 	return generic_parse_monolithic(fc, data);
392 }
393 
vboxsf_get_tree(struct fs_context * fc)394 static int vboxsf_get_tree(struct fs_context *fc)
395 {
396 	int err;
397 
398 	err = vboxsf_setup();
399 	if (err)
400 		return err;
401 
402 	return get_tree_nodev(fc, vboxsf_fill_super);
403 }
404 
vboxsf_reconfigure(struct fs_context * fc)405 static int vboxsf_reconfigure(struct fs_context *fc)
406 {
407 	struct vboxsf_sbi *sbi = VBOXSF_SBI(fc->root->d_sb);
408 	struct vboxsf_fs_context *ctx = fc->fs_private;
409 	struct inode *iroot = fc->root->d_sb->s_root->d_inode;
410 
411 	/* Apply changed options to the root inode */
412 	sbi->o = ctx->o;
413 	vboxsf_init_inode(sbi, iroot, &sbi->root_info, true);
414 
415 	return 0;
416 }
417 
vboxsf_free_fc(struct fs_context * fc)418 static void vboxsf_free_fc(struct fs_context *fc)
419 {
420 	struct vboxsf_fs_context *ctx = fc->fs_private;
421 
422 	kfree(ctx->nls_name);
423 	kfree(ctx);
424 }
425 
426 static const struct fs_context_operations vboxsf_context_ops = {
427 	.free			= vboxsf_free_fc,
428 	.parse_param		= vboxsf_parse_param,
429 	.parse_monolithic	= vboxsf_parse_monolithic,
430 	.get_tree		= vboxsf_get_tree,
431 	.reconfigure		= vboxsf_reconfigure,
432 };
433 
vboxsf_init_fs_context(struct fs_context * fc)434 static int vboxsf_init_fs_context(struct fs_context *fc)
435 {
436 	struct vboxsf_fs_context *ctx;
437 
438 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
439 	if (!ctx)
440 		return -ENOMEM;
441 
442 	current_uid_gid(&ctx->o.uid, &ctx->o.gid);
443 
444 	fc->fs_private = ctx;
445 	fc->ops = &vboxsf_context_ops;
446 	return 0;
447 }
448 
449 static struct file_system_type vboxsf_fs_type = {
450 	.owner			= THIS_MODULE,
451 	.name			= "vboxsf",
452 	.init_fs_context	= vboxsf_init_fs_context,
453 	.kill_sb		= kill_anon_super
454 };
455 
456 /* Module initialization/finalization handlers */
vboxsf_init(void)457 static int __init vboxsf_init(void)
458 {
459 	return register_filesystem(&vboxsf_fs_type);
460 }
461 
vboxsf_fini(void)462 static void __exit vboxsf_fini(void)
463 {
464 	unregister_filesystem(&vboxsf_fs_type);
465 
466 	mutex_lock(&vboxsf_setup_mutex);
467 	if (vboxsf_setup_done) {
468 		vboxsf_disconnect();
469 		/*
470 		 * Make sure all delayed rcu free inodes are flushed
471 		 * before we destroy the cache.
472 		 */
473 		rcu_barrier();
474 		kmem_cache_destroy(vboxsf_inode_cachep);
475 	}
476 	mutex_unlock(&vboxsf_setup_mutex);
477 }
478 
479 module_init(vboxsf_init);
480 module_exit(vboxsf_fini);
481 
482 MODULE_DESCRIPTION("Oracle VM VirtualBox Module for Host File System Access");
483 MODULE_AUTHOR("Oracle Corporation");
484 MODULE_LICENSE("GPL v2");
485 MODULE_ALIAS_FS("vboxsf");
486