1 /*
2 FUSE: Filesystem in Userspace
3 Copyright (C) 2001-2008 Miklos Szeredi <miklos@szeredi.hu>
4
5 This program can be distributed under the terms of the GNU GPL.
6 See the file COPYING.
7 */
8
9 #include "fuse_i.h"
10
11 #include <linux/init.h>
12 #include <linux/module.h>
13 #include <linux/fs_context.h>
14
15 #define FUSE_CTL_SUPER_MAGIC 0x65735543
16
17 /*
18 * This is non-NULL when the single instance of the control filesystem
19 * exists. Protected by fuse_mutex
20 */
21 static struct super_block *fuse_control_sb;
22
fuse_ctl_file_conn_get(struct file * file)23 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
24 {
25 struct fuse_conn *fc;
26 mutex_lock(&fuse_mutex);
27 fc = file_inode(file)->i_private;
28 if (fc)
29 fc = fuse_conn_get(fc);
30 mutex_unlock(&fuse_mutex);
31 return fc;
32 }
33
fuse_conn_abort_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)34 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
35 size_t count, loff_t *ppos)
36 {
37 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
38 if (fc) {
39 if (fc->abort_err)
40 fc->aborted = true;
41 fuse_abort_conn(fc);
42 fuse_conn_put(fc);
43 }
44 return count;
45 }
46
fuse_conn_waiting_read(struct file * file,char __user * buf,size_t len,loff_t * ppos)47 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
48 size_t len, loff_t *ppos)
49 {
50 char tmp[32];
51 size_t size;
52
53 if (!*ppos) {
54 long value;
55 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
56 if (!fc)
57 return 0;
58
59 value = atomic_read(&fc->num_waiting);
60 file->private_data = (void *)value;
61 fuse_conn_put(fc);
62 }
63 size = sprintf(tmp, "%ld\n", (long)file->private_data);
64 return simple_read_from_buffer(buf, len, ppos, tmp, size);
65 }
66
fuse_conn_limit_read(struct file * file,char __user * buf,size_t len,loff_t * ppos,unsigned val)67 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
68 size_t len, loff_t *ppos, unsigned val)
69 {
70 char tmp[32];
71 size_t size = sprintf(tmp, "%u\n", val);
72
73 return simple_read_from_buffer(buf, len, ppos, tmp, size);
74 }
75
fuse_conn_limit_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos,unsigned * val,unsigned global_limit)76 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
77 size_t count, loff_t *ppos, unsigned *val,
78 unsigned global_limit)
79 {
80 unsigned long t;
81 unsigned limit = (1 << 16) - 1;
82 int err;
83
84 if (*ppos)
85 return -EINVAL;
86
87 err = kstrtoul_from_user(buf, count, 0, &t);
88 if (err)
89 return err;
90
91 if (!capable(CAP_SYS_ADMIN))
92 limit = min(limit, global_limit);
93
94 if (t > limit)
95 return -EINVAL;
96
97 *val = t;
98
99 return count;
100 }
101
fuse_conn_max_background_read(struct file * file,char __user * buf,size_t len,loff_t * ppos)102 static ssize_t fuse_conn_max_background_read(struct file *file,
103 char __user *buf, size_t len,
104 loff_t *ppos)
105 {
106 struct fuse_conn *fc;
107 unsigned val;
108
109 fc = fuse_ctl_file_conn_get(file);
110 if (!fc)
111 return 0;
112
113 val = READ_ONCE(fc->max_background);
114 fuse_conn_put(fc);
115
116 return fuse_conn_limit_read(file, buf, len, ppos, val);
117 }
118
fuse_conn_max_background_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)119 static ssize_t fuse_conn_max_background_write(struct file *file,
120 const char __user *buf,
121 size_t count, loff_t *ppos)
122 {
123 unsigned val;
124 ssize_t ret;
125
126 ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
127 max_user_bgreq);
128 if (ret > 0) {
129 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
130 if (fc) {
131 spin_lock(&fc->bg_lock);
132 fc->max_background = val;
133 fc->blocked = fc->num_background >= fc->max_background;
134 if (!fc->blocked)
135 wake_up(&fc->blocked_waitq);
136 spin_unlock(&fc->bg_lock);
137 fuse_conn_put(fc);
138 }
139 }
140
141 return ret;
142 }
143
fuse_conn_congestion_threshold_read(struct file * file,char __user * buf,size_t len,loff_t * ppos)144 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
145 char __user *buf, size_t len,
146 loff_t *ppos)
147 {
148 struct fuse_conn *fc;
149 unsigned val;
150
151 fc = fuse_ctl_file_conn_get(file);
152 if (!fc)
153 return 0;
154
155 val = READ_ONCE(fc->congestion_threshold);
156 fuse_conn_put(fc);
157
158 return fuse_conn_limit_read(file, buf, len, ppos, val);
159 }
160
fuse_conn_congestion_threshold_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)161 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
162 const char __user *buf,
163 size_t count, loff_t *ppos)
164 {
165 unsigned val;
166 struct fuse_conn *fc;
167 ssize_t ret;
168
169 ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
170 max_user_congthresh);
171 if (ret <= 0)
172 goto out;
173 fc = fuse_ctl_file_conn_get(file);
174 if (!fc)
175 goto out;
176
177 down_read(&fc->killsb);
178 spin_lock(&fc->bg_lock);
179 fc->congestion_threshold = val;
180 spin_unlock(&fc->bg_lock);
181 up_read(&fc->killsb);
182 fuse_conn_put(fc);
183 out:
184 return ret;
185 }
186
187 static const struct file_operations fuse_ctl_abort_ops = {
188 .open = nonseekable_open,
189 .write = fuse_conn_abort_write,
190 .llseek = no_llseek,
191 };
192
193 static const struct file_operations fuse_ctl_waiting_ops = {
194 .open = nonseekable_open,
195 .read = fuse_conn_waiting_read,
196 .llseek = no_llseek,
197 };
198
199 static const struct file_operations fuse_conn_max_background_ops = {
200 .open = nonseekable_open,
201 .read = fuse_conn_max_background_read,
202 .write = fuse_conn_max_background_write,
203 .llseek = no_llseek,
204 };
205
206 static const struct file_operations fuse_conn_congestion_threshold_ops = {
207 .open = nonseekable_open,
208 .read = fuse_conn_congestion_threshold_read,
209 .write = fuse_conn_congestion_threshold_write,
210 .llseek = no_llseek,
211 };
212
fuse_ctl_add_dentry(struct dentry * parent,struct fuse_conn * fc,const char * name,int mode,int nlink,const struct inode_operations * iop,const struct file_operations * fop)213 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
214 struct fuse_conn *fc,
215 const char *name,
216 int mode, int nlink,
217 const struct inode_operations *iop,
218 const struct file_operations *fop)
219 {
220 struct dentry *dentry;
221 struct inode *inode;
222
223 BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
224 dentry = d_alloc_name(parent, name);
225 if (!dentry)
226 return NULL;
227
228 inode = new_inode(fuse_control_sb);
229 if (!inode) {
230 dput(dentry);
231 return NULL;
232 }
233
234 inode->i_ino = get_next_ino();
235 inode->i_mode = mode;
236 inode->i_uid = fc->user_id;
237 inode->i_gid = fc->group_id;
238 inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
239 /* setting ->i_op to NULL is not allowed */
240 if (iop)
241 inode->i_op = iop;
242 inode->i_fop = fop;
243 set_nlink(inode, nlink);
244 inode->i_private = fc;
245 d_add(dentry, inode);
246
247 fc->ctl_dentry[fc->ctl_ndents++] = dentry;
248
249 return dentry;
250 }
251
252 /*
253 * Add a connection to the control filesystem (if it exists). Caller
254 * must hold fuse_mutex
255 */
fuse_ctl_add_conn(struct fuse_conn * fc)256 int fuse_ctl_add_conn(struct fuse_conn *fc)
257 {
258 struct dentry *parent;
259 char name[32];
260
261 if (!fuse_control_sb || fc->no_control)
262 return 0;
263
264 parent = fuse_control_sb->s_root;
265 inc_nlink(d_inode(parent));
266 sprintf(name, "%u", fc->dev);
267 parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
268 &simple_dir_inode_operations,
269 &simple_dir_operations);
270 if (!parent)
271 goto err;
272
273 if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
274 NULL, &fuse_ctl_waiting_ops) ||
275 !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
276 NULL, &fuse_ctl_abort_ops) ||
277 !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
278 1, NULL, &fuse_conn_max_background_ops) ||
279 !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
280 S_IFREG | 0600, 1, NULL,
281 &fuse_conn_congestion_threshold_ops))
282 goto err;
283
284 return 0;
285
286 err:
287 fuse_ctl_remove_conn(fc);
288 return -ENOMEM;
289 }
290
291 /*
292 * Remove a connection from the control filesystem (if it exists).
293 * Caller must hold fuse_mutex
294 */
fuse_ctl_remove_conn(struct fuse_conn * fc)295 void fuse_ctl_remove_conn(struct fuse_conn *fc)
296 {
297 int i;
298
299 if (!fuse_control_sb || fc->no_control)
300 return;
301
302 for (i = fc->ctl_ndents - 1; i >= 0; i--) {
303 struct dentry *dentry = fc->ctl_dentry[i];
304 d_inode(dentry)->i_private = NULL;
305 if (!i) {
306 /* Get rid of submounts: */
307 d_invalidate(dentry);
308 }
309 dput(dentry);
310 }
311 drop_nlink(d_inode(fuse_control_sb->s_root));
312 }
313
fuse_ctl_fill_super(struct super_block * sb,struct fs_context * fsc)314 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
315 {
316 static const struct tree_descr empty_descr = {""};
317 struct fuse_conn *fc;
318 int err;
319
320 err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
321 if (err)
322 return err;
323
324 mutex_lock(&fuse_mutex);
325 BUG_ON(fuse_control_sb);
326 fuse_control_sb = sb;
327 list_for_each_entry(fc, &fuse_conn_list, entry) {
328 err = fuse_ctl_add_conn(fc);
329 if (err) {
330 fuse_control_sb = NULL;
331 mutex_unlock(&fuse_mutex);
332 return err;
333 }
334 }
335 mutex_unlock(&fuse_mutex);
336
337 return 0;
338 }
339
fuse_ctl_get_tree(struct fs_context * fsc)340 static int fuse_ctl_get_tree(struct fs_context *fsc)
341 {
342 return get_tree_single(fsc, fuse_ctl_fill_super);
343 }
344
345 static const struct fs_context_operations fuse_ctl_context_ops = {
346 .get_tree = fuse_ctl_get_tree,
347 };
348
fuse_ctl_init_fs_context(struct fs_context * fsc)349 static int fuse_ctl_init_fs_context(struct fs_context *fsc)
350 {
351 fsc->ops = &fuse_ctl_context_ops;
352 return 0;
353 }
354
fuse_ctl_kill_sb(struct super_block * sb)355 static void fuse_ctl_kill_sb(struct super_block *sb)
356 {
357 struct fuse_conn *fc;
358
359 mutex_lock(&fuse_mutex);
360 fuse_control_sb = NULL;
361 list_for_each_entry(fc, &fuse_conn_list, entry)
362 fc->ctl_ndents = 0;
363 mutex_unlock(&fuse_mutex);
364
365 kill_litter_super(sb);
366 }
367
368 static struct file_system_type fuse_ctl_fs_type = {
369 .owner = THIS_MODULE,
370 .name = "fusectl",
371 .init_fs_context = fuse_ctl_init_fs_context,
372 .kill_sb = fuse_ctl_kill_sb,
373 };
374 MODULE_ALIAS_FS("fusectl");
375
fuse_ctl_init(void)376 int __init fuse_ctl_init(void)
377 {
378 return register_filesystem(&fuse_ctl_fs_type);
379 }
380
fuse_ctl_cleanup(void)381 void __exit fuse_ctl_cleanup(void)
382 {
383 unregister_filesystem(&fuse_ctl_fs_type);
384 }
385