KVM: arm64: Enable Address Authentication at EL2 if available
[linux-2.6-microblaze.git] / drivers / base / devtmpfs.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * devtmpfs - kernel-maintained tmpfs-based /dev
4  *
5  * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
6  *
7  * During bootup, before any driver core device is registered,
8  * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
9  * device which requests a device node, will add a node in this
10  * filesystem.
11  * By default, all devices are named after the name of the device,
12  * owned by root and have a default mode of 0600. Subsystems can
13  * overwrite the default setting if needed.
14  */
15
16 #include <linux/kernel.h>
17 #include <linux/syscalls.h>
18 #include <linux/mount.h>
19 #include <linux/device.h>
20 #include <linux/genhd.h>
21 #include <linux/namei.h>
22 #include <linux/fs.h>
23 #include <linux/shmem_fs.h>
24 #include <linux/ramfs.h>
25 #include <linux/sched.h>
26 #include <linux/slab.h>
27 #include <linux/kthread.h>
28 #include <uapi/linux/mount.h>
29 #include "base.h"
30
31 static struct task_struct *thread;
32
33 static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT);
34
35 static DEFINE_SPINLOCK(req_lock);
36
37 static struct req {
38         struct req *next;
39         struct completion done;
40         int err;
41         const char *name;
42         umode_t mode;   /* 0 => delete */
43         kuid_t uid;
44         kgid_t gid;
45         struct device *dev;
46 } *requests;
47
48 static int __init mount_param(char *str)
49 {
50         mount_dev = simple_strtoul(str, NULL, 0);
51         return 1;
52 }
53 __setup("devtmpfs.mount=", mount_param);
54
55 static struct vfsmount *mnt;
56
57 static struct dentry *public_dev_mount(struct file_system_type *fs_type, int flags,
58                       const char *dev_name, void *data)
59 {
60         struct super_block *s = mnt->mnt_sb;
61         atomic_inc(&s->s_active);
62         down_write(&s->s_umount);
63         return dget(s->s_root);
64 }
65
66 static struct file_system_type internal_fs_type = {
67         .name = "devtmpfs",
68 #ifdef CONFIG_TMPFS
69         .init_fs_context = shmem_init_fs_context,
70         .parameters     = shmem_fs_parameters,
71 #else
72         .init_fs_context = ramfs_init_fs_context,
73         .parameters     = ramfs_fs_parameters,
74 #endif
75         .kill_sb = kill_litter_super,
76 };
77
78 static struct file_system_type dev_fs_type = {
79         .name = "devtmpfs",
80         .mount = public_dev_mount,
81 };
82
83 #ifdef CONFIG_BLOCK
84 static inline int is_blockdev(struct device *dev)
85 {
86         return dev->class == &block_class;
87 }
88 #else
89 static inline int is_blockdev(struct device *dev) { return 0; }
90 #endif
91
92 static int devtmpfs_submit_req(struct req *req, const char *tmp)
93 {
94         init_completion(&req->done);
95
96         spin_lock(&req_lock);
97         req->next = requests;
98         requests = req;
99         spin_unlock(&req_lock);
100
101         wake_up_process(thread);
102         wait_for_completion(&req->done);
103
104         kfree(tmp);
105
106         return req->err;
107 }
108
109 int devtmpfs_create_node(struct device *dev)
110 {
111         const char *tmp = NULL;
112         struct req req;
113
114         if (!thread)
115                 return 0;
116
117         req.mode = 0;
118         req.uid = GLOBAL_ROOT_UID;
119         req.gid = GLOBAL_ROOT_GID;
120         req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
121         if (!req.name)
122                 return -ENOMEM;
123
124         if (req.mode == 0)
125                 req.mode = 0600;
126         if (is_blockdev(dev))
127                 req.mode |= S_IFBLK;
128         else
129                 req.mode |= S_IFCHR;
130
131         req.dev = dev;
132
133         return devtmpfs_submit_req(&req, tmp);
134 }
135
136 int devtmpfs_delete_node(struct device *dev)
137 {
138         const char *tmp = NULL;
139         struct req req;
140
141         if (!thread)
142                 return 0;
143
144         req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
145         if (!req.name)
146                 return -ENOMEM;
147
148         req.mode = 0;
149         req.dev = dev;
150
151         return devtmpfs_submit_req(&req, tmp);
152 }
153
154 static int dev_mkdir(const char *name, umode_t mode)
155 {
156         struct dentry *dentry;
157         struct path path;
158         int err;
159
160         dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
161         if (IS_ERR(dentry))
162                 return PTR_ERR(dentry);
163
164         err = vfs_mkdir(d_inode(path.dentry), dentry, mode);
165         if (!err)
166                 /* mark as kernel-created inode */
167                 d_inode(dentry)->i_private = &thread;
168         done_path_create(&path, dentry);
169         return err;
170 }
171
172 static int create_path(const char *nodepath)
173 {
174         char *path;
175         char *s;
176         int err = 0;
177
178         /* parent directories do not exist, create them */
179         path = kstrdup(nodepath, GFP_KERNEL);
180         if (!path)
181                 return -ENOMEM;
182
183         s = path;
184         for (;;) {
185                 s = strchr(s, '/');
186                 if (!s)
187                         break;
188                 s[0] = '\0';
189                 err = dev_mkdir(path, 0755);
190                 if (err && err != -EEXIST)
191                         break;
192                 s[0] = '/';
193                 s++;
194         }
195         kfree(path);
196         return err;
197 }
198
199 static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
200                          kgid_t gid, struct device *dev)
201 {
202         struct dentry *dentry;
203         struct path path;
204         int err;
205
206         dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
207         if (dentry == ERR_PTR(-ENOENT)) {
208                 create_path(nodename);
209                 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
210         }
211         if (IS_ERR(dentry))
212                 return PTR_ERR(dentry);
213
214         err = vfs_mknod(d_inode(path.dentry), dentry, mode, dev->devt);
215         if (!err) {
216                 struct iattr newattrs;
217
218                 newattrs.ia_mode = mode;
219                 newattrs.ia_uid = uid;
220                 newattrs.ia_gid = gid;
221                 newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
222                 inode_lock(d_inode(dentry));
223                 notify_change(dentry, &newattrs, NULL);
224                 inode_unlock(d_inode(dentry));
225
226                 /* mark as kernel-created inode */
227                 d_inode(dentry)->i_private = &thread;
228         }
229         done_path_create(&path, dentry);
230         return err;
231 }
232
233 static int dev_rmdir(const char *name)
234 {
235         struct path parent;
236         struct dentry *dentry;
237         int err;
238
239         dentry = kern_path_locked(name, &parent);
240         if (IS_ERR(dentry))
241                 return PTR_ERR(dentry);
242         if (d_really_is_positive(dentry)) {
243                 if (d_inode(dentry)->i_private == &thread)
244                         err = vfs_rmdir(d_inode(parent.dentry), dentry);
245                 else
246                         err = -EPERM;
247         } else {
248                 err = -ENOENT;
249         }
250         dput(dentry);
251         inode_unlock(d_inode(parent.dentry));
252         path_put(&parent);
253         return err;
254 }
255
256 static int delete_path(const char *nodepath)
257 {
258         char *path;
259         int err = 0;
260
261         path = kstrdup(nodepath, GFP_KERNEL);
262         if (!path)
263                 return -ENOMEM;
264
265         for (;;) {
266                 char *base;
267
268                 base = strrchr(path, '/');
269                 if (!base)
270                         break;
271                 base[0] = '\0';
272                 err = dev_rmdir(path);
273                 if (err)
274                         break;
275         }
276
277         kfree(path);
278         return err;
279 }
280
281 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
282 {
283         /* did we create it */
284         if (inode->i_private != &thread)
285                 return 0;
286
287         /* does the dev_t match */
288         if (is_blockdev(dev)) {
289                 if (!S_ISBLK(stat->mode))
290                         return 0;
291         } else {
292                 if (!S_ISCHR(stat->mode))
293                         return 0;
294         }
295         if (stat->rdev != dev->devt)
296                 return 0;
297
298         /* ours */
299         return 1;
300 }
301
302 static int handle_remove(const char *nodename, struct device *dev)
303 {
304         struct path parent;
305         struct dentry *dentry;
306         int deleted = 0;
307         int err;
308
309         dentry = kern_path_locked(nodename, &parent);
310         if (IS_ERR(dentry))
311                 return PTR_ERR(dentry);
312
313         if (d_really_is_positive(dentry)) {
314                 struct kstat stat;
315                 struct path p = {.mnt = parent.mnt, .dentry = dentry};
316                 err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
317                                   AT_STATX_SYNC_AS_STAT);
318                 if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
319                         struct iattr newattrs;
320                         /*
321                          * before unlinking this node, reset permissions
322                          * of possible references like hardlinks
323                          */
324                         newattrs.ia_uid = GLOBAL_ROOT_UID;
325                         newattrs.ia_gid = GLOBAL_ROOT_GID;
326                         newattrs.ia_mode = stat.mode & ~0777;
327                         newattrs.ia_valid =
328                                 ATTR_UID|ATTR_GID|ATTR_MODE;
329                         inode_lock(d_inode(dentry));
330                         notify_change(dentry, &newattrs, NULL);
331                         inode_unlock(d_inode(dentry));
332                         err = vfs_unlink(d_inode(parent.dentry), dentry, NULL);
333                         if (!err || err == -ENOENT)
334                                 deleted = 1;
335                 }
336         } else {
337                 err = -ENOENT;
338         }
339         dput(dentry);
340         inode_unlock(d_inode(parent.dentry));
341
342         path_put(&parent);
343         if (deleted && strchr(nodename, '/'))
344                 delete_path(nodename);
345         return err;
346 }
347
348 /*
349  * If configured, or requested by the commandline, devtmpfs will be
350  * auto-mounted after the kernel mounted the root filesystem.
351  */
352 int __init devtmpfs_mount(void)
353 {
354         int err;
355
356         if (!mount_dev)
357                 return 0;
358
359         if (!thread)
360                 return 0;
361
362         err = do_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL);
363         if (err)
364                 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
365         else
366                 printk(KERN_INFO "devtmpfs: mounted\n");
367         return err;
368 }
369
370 static DECLARE_COMPLETION(setup_done);
371
372 static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
373                   struct device *dev)
374 {
375         if (mode)
376                 return handle_create(name, mode, uid, gid, dev);
377         else
378                 return handle_remove(name, dev);
379 }
380
381 static int devtmpfs_setup(void *p)
382 {
383         int err;
384
385         err = ksys_unshare(CLONE_NEWNS);
386         if (err)
387                 goto out;
388         err = do_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL);
389         if (err)
390                 goto out;
391         ksys_chdir("/.."); /* will traverse into overmounted root */
392         ksys_chroot(".");
393 out:
394         *(int *)p = err;
395         complete(&setup_done);
396         return err;
397 }
398
399 static int devtmpfsd(void *p)
400 {
401         int err = devtmpfs_setup(p);
402
403         if (err)
404                 return err;
405         while (1) {
406                 spin_lock(&req_lock);
407                 while (requests) {
408                         struct req *req = requests;
409                         requests = NULL;
410                         spin_unlock(&req_lock);
411                         while (req) {
412                                 struct req *next = req->next;
413                                 req->err = handle(req->name, req->mode,
414                                                   req->uid, req->gid, req->dev);
415                                 complete(&req->done);
416                                 req = next;
417                         }
418                         spin_lock(&req_lock);
419                 }
420                 __set_current_state(TASK_INTERRUPTIBLE);
421                 spin_unlock(&req_lock);
422                 schedule();
423         }
424         return 0;
425 }
426
427 /*
428  * Create devtmpfs instance, driver-core devices will add their device
429  * nodes here.
430  */
431 int __init devtmpfs_init(void)
432 {
433         char opts[] = "mode=0755";
434         int err;
435
436         mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts);
437         if (IS_ERR(mnt)) {
438                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %ld\n",
439                                 PTR_ERR(mnt));
440                 return PTR_ERR(mnt);
441         }
442         err = register_filesystem(&dev_fs_type);
443         if (err) {
444                 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
445                        "type %i\n", err);
446                 return err;
447         }
448
449         thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
450         if (!IS_ERR(thread)) {
451                 wait_for_completion(&setup_done);
452         } else {
453                 err = PTR_ERR(thread);
454                 thread = NULL;
455         }
456
457         if (err) {
458                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
459                 unregister_filesystem(&dev_fs_type);
460                 return err;
461         }
462
463         printk(KERN_INFO "devtmpfs: initialized\n");
464         return 0;
465 }