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Linux/fs/proc/inode.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/fs/proc/inode.c
  4  *
  5  *  Copyright (C) 1991, 1992  Linus Torvalds
  6  */
  7 
  8 #include <linux/cache.h>
  9 #include <linux/time.h>
 10 #include <linux/proc_fs.h>
 11 #include <linux/kernel.h>
 12 #include <linux/pid_namespace.h>
 13 #include <linux/mm.h>
 14 #include <linux/string.h>
 15 #include <linux/stat.h>
 16 #include <linux/completion.h>
 17 #include <linux/poll.h>
 18 #include <linux/printk.h>
 19 #include <linux/file.h>
 20 #include <linux/limits.h>
 21 #include <linux/init.h>
 22 #include <linux/module.h>
 23 #include <linux/sysctl.h>
 24 #include <linux/seq_file.h>
 25 #include <linux/slab.h>
 26 #include <linux/mount.h>
 27 #include <linux/magic.h>
 28 
 29 #include <linux/uaccess.h>
 30 
 31 #include "internal.h"
 32 
 33 static void proc_evict_inode(struct inode *inode)
 34 {
 35         struct proc_dir_entry *de;
 36         struct ctl_table_header *head;
 37 
 38         truncate_inode_pages_final(&inode->i_data);
 39         clear_inode(inode);
 40 
 41         /* Stop tracking associated processes */
 42         put_pid(PROC_I(inode)->pid);
 43 
 44         /* Let go of any associated proc directory entry */
 45         de = PDE(inode);
 46         if (de)
 47                 pde_put(de);
 48 
 49         head = PROC_I(inode)->sysctl;
 50         if (head) {
 51                 RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
 52                 proc_sys_evict_inode(inode, head);
 53         }
 54 }
 55 
 56 static struct kmem_cache *proc_inode_cachep __ro_after_init;
 57 static struct kmem_cache *pde_opener_cache __ro_after_init;
 58 
 59 static struct inode *proc_alloc_inode(struct super_block *sb)
 60 {
 61         struct proc_inode *ei;
 62         struct inode *inode;
 63 
 64         ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
 65         if (!ei)
 66                 return NULL;
 67         ei->pid = NULL;
 68         ei->fd = 0;
 69         ei->op.proc_get_link = NULL;
 70         ei->pde = NULL;
 71         ei->sysctl = NULL;
 72         ei->sysctl_entry = NULL;
 73         ei->ns_ops = NULL;
 74         inode = &ei->vfs_inode;
 75         return inode;
 76 }
 77 
 78 static void proc_i_callback(struct rcu_head *head)
 79 {
 80         struct inode *inode = container_of(head, struct inode, i_rcu);
 81         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
 82 }
 83 
 84 static void proc_destroy_inode(struct inode *inode)
 85 {
 86         call_rcu(&inode->i_rcu, proc_i_callback);
 87 }
 88 
 89 static void init_once(void *foo)
 90 {
 91         struct proc_inode *ei = (struct proc_inode *) foo;
 92 
 93         inode_init_once(&ei->vfs_inode);
 94 }
 95 
 96 void __init proc_init_kmemcache(void)
 97 {
 98         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
 99                                              sizeof(struct proc_inode),
100                                              0, (SLAB_RECLAIM_ACCOUNT|
101                                                 SLAB_MEM_SPREAD|SLAB_ACCOUNT|
102                                                 SLAB_PANIC),
103                                              init_once);
104         pde_opener_cache =
105                 kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,
106                                   SLAB_ACCOUNT|SLAB_PANIC, NULL);
107         proc_dir_entry_cache = kmem_cache_create_usercopy(
108                 "proc_dir_entry", SIZEOF_PDE_SLOT, 0, SLAB_PANIC,
109                 OFFSETOF_PDE_NAME, SIZEOF_PDE_INLINE_NAME, NULL);
110 }
111 
112 static int proc_show_options(struct seq_file *seq, struct dentry *root)
113 {
114         struct super_block *sb = root->d_sb;
115         struct pid_namespace *pid = sb->s_fs_info;
116 
117         if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
118                 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
119         if (pid->hide_pid != HIDEPID_OFF)
120                 seq_printf(seq, ",hidepid=%u", pid->hide_pid);
121 
122         return 0;
123 }
124 
125 static const struct super_operations proc_sops = {
126         .alloc_inode    = proc_alloc_inode,
127         .destroy_inode  = proc_destroy_inode,
128         .drop_inode     = generic_delete_inode,
129         .evict_inode    = proc_evict_inode,
130         .statfs         = simple_statfs,
131         .remount_fs     = proc_remount,
132         .show_options   = proc_show_options,
133 };
134 
135 enum {BIAS = -1U<<31};
136 
137 static inline int use_pde(struct proc_dir_entry *pde)
138 {
139         return likely(atomic_inc_unless_negative(&pde->in_use));
140 }
141 
142 static void unuse_pde(struct proc_dir_entry *pde)
143 {
144         if (unlikely(atomic_dec_return(&pde->in_use) == BIAS))
145                 complete(pde->pde_unload_completion);
146 }
147 
148 /* pde is locked on entry, unlocked on exit */
149 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
150 {
151         /*
152          * close() (proc_reg_release()) can't delete an entry and proceed:
153          * ->release hook needs to be available at the right moment.
154          *
155          * rmmod (remove_proc_entry() et al) can't delete an entry and proceed:
156          * "struct file" needs to be available at the right moment.
157          *
158          * Therefore, first process to enter this function does ->release() and
159          * signals its completion to the other process which does nothing.
160          */
161         if (pdeo->closing) {
162                 /* somebody else is doing that, just wait */
163                 DECLARE_COMPLETION_ONSTACK(c);
164                 pdeo->c = &c;
165                 spin_unlock(&pde->pde_unload_lock);
166                 wait_for_completion(&c);
167         } else {
168                 struct file *file;
169                 struct completion *c;
170 
171                 pdeo->closing = true;
172                 spin_unlock(&pde->pde_unload_lock);
173                 file = pdeo->file;
174                 pde->proc_fops->release(file_inode(file), file);
175                 spin_lock(&pde->pde_unload_lock);
176                 /* After ->release. */
177                 list_del(&pdeo->lh);
178                 c = pdeo->c;
179                 spin_unlock(&pde->pde_unload_lock);
180                 if (unlikely(c))
181                         complete(c);
182                 kmem_cache_free(pde_opener_cache, pdeo);
183         }
184 }
185 
186 void proc_entry_rundown(struct proc_dir_entry *de)
187 {
188         DECLARE_COMPLETION_ONSTACK(c);
189         /* Wait until all existing callers into module are done. */
190         de->pde_unload_completion = &c;
191         if (atomic_add_return(BIAS, &de->in_use) != BIAS)
192                 wait_for_completion(&c);
193 
194         /* ->pde_openers list can't grow from now on. */
195 
196         spin_lock(&de->pde_unload_lock);
197         while (!list_empty(&de->pde_openers)) {
198                 struct pde_opener *pdeo;
199                 pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
200                 close_pdeo(de, pdeo);
201                 spin_lock(&de->pde_unload_lock);
202         }
203         spin_unlock(&de->pde_unload_lock);
204 }
205 
206 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
207 {
208         struct proc_dir_entry *pde = PDE(file_inode(file));
209         loff_t rv = -EINVAL;
210         if (use_pde(pde)) {
211                 loff_t (*llseek)(struct file *, loff_t, int);
212                 llseek = pde->proc_fops->llseek;
213                 if (!llseek)
214                         llseek = default_llseek;
215                 rv = llseek(file, offset, whence);
216                 unuse_pde(pde);
217         }
218         return rv;
219 }
220 
221 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
222 {
223         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
224         struct proc_dir_entry *pde = PDE(file_inode(file));
225         ssize_t rv = -EIO;
226         if (use_pde(pde)) {
227                 read = pde->proc_fops->read;
228                 if (read)
229                         rv = read(file, buf, count, ppos);
230                 unuse_pde(pde);
231         }
232         return rv;
233 }
234 
235 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
236 {
237         ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
238         struct proc_dir_entry *pde = PDE(file_inode(file));
239         ssize_t rv = -EIO;
240         if (use_pde(pde)) {
241                 write = pde->proc_fops->write;
242                 if (write)
243                         rv = write(file, buf, count, ppos);
244                 unuse_pde(pde);
245         }
246         return rv;
247 }
248 
249 static __poll_t proc_reg_poll(struct file *file, struct poll_table_struct *pts)
250 {
251         struct proc_dir_entry *pde = PDE(file_inode(file));
252         __poll_t rv = DEFAULT_POLLMASK;
253         __poll_t (*poll)(struct file *, struct poll_table_struct *);
254         if (use_pde(pde)) {
255                 poll = pde->proc_fops->poll;
256                 if (poll)
257                         rv = poll(file, pts);
258                 unuse_pde(pde);
259         }
260         return rv;
261 }
262 
263 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
264 {
265         struct proc_dir_entry *pde = PDE(file_inode(file));
266         long rv = -ENOTTY;
267         long (*ioctl)(struct file *, unsigned int, unsigned long);
268         if (use_pde(pde)) {
269                 ioctl = pde->proc_fops->unlocked_ioctl;
270                 if (ioctl)
271                         rv = ioctl(file, cmd, arg);
272                 unuse_pde(pde);
273         }
274         return rv;
275 }
276 
277 #ifdef CONFIG_COMPAT
278 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
279 {
280         struct proc_dir_entry *pde = PDE(file_inode(file));
281         long rv = -ENOTTY;
282         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
283         if (use_pde(pde)) {
284                 compat_ioctl = pde->proc_fops->compat_ioctl;
285                 if (compat_ioctl)
286                         rv = compat_ioctl(file, cmd, arg);
287                 unuse_pde(pde);
288         }
289         return rv;
290 }
291 #endif
292 
293 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
294 {
295         struct proc_dir_entry *pde = PDE(file_inode(file));
296         int rv = -EIO;
297         int (*mmap)(struct file *, struct vm_area_struct *);
298         if (use_pde(pde)) {
299                 mmap = pde->proc_fops->mmap;
300                 if (mmap)
301                         rv = mmap(file, vma);
302                 unuse_pde(pde);
303         }
304         return rv;
305 }
306 
307 static unsigned long
308 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
309                            unsigned long len, unsigned long pgoff,
310                            unsigned long flags)
311 {
312         struct proc_dir_entry *pde = PDE(file_inode(file));
313         unsigned long rv = -EIO;
314 
315         if (use_pde(pde)) {
316                 typeof(proc_reg_get_unmapped_area) *get_area;
317 
318                 get_area = pde->proc_fops->get_unmapped_area;
319 #ifdef CONFIG_MMU
320                 if (!get_area)
321                         get_area = current->mm->get_unmapped_area;
322 #endif
323 
324                 if (get_area)
325                         rv = get_area(file, orig_addr, len, pgoff, flags);
326                 else
327                         rv = orig_addr;
328                 unuse_pde(pde);
329         }
330         return rv;
331 }
332 
333 static int proc_reg_open(struct inode *inode, struct file *file)
334 {
335         struct proc_dir_entry *pde = PDE(inode);
336         int rv = 0;
337         int (*open)(struct inode *, struct file *);
338         int (*release)(struct inode *, struct file *);
339         struct pde_opener *pdeo;
340 
341         /*
342          * Ensure that
343          * 1) PDE's ->release hook will be called no matter what
344          *    either normally by close()/->release, or forcefully by
345          *    rmmod/remove_proc_entry.
346          *
347          * 2) rmmod isn't blocked by opening file in /proc and sitting on
348          *    the descriptor (including "rmmod foo </proc/foo" scenario).
349          *
350          * Save every "struct file" with custom ->release hook.
351          */
352         if (!use_pde(pde))
353                 return -ENOENT;
354 
355         release = pde->proc_fops->release;
356         if (release) {
357                 pdeo = kmem_cache_alloc(pde_opener_cache, GFP_KERNEL);
358                 if (!pdeo) {
359                         rv = -ENOMEM;
360                         goto out_unuse;
361                 }
362         }
363 
364         open = pde->proc_fops->open;
365         if (open)
366                 rv = open(inode, file);
367 
368         if (release) {
369                 if (rv == 0) {
370                         /* To know what to release. */
371                         pdeo->file = file;
372                         pdeo->closing = false;
373                         pdeo->c = NULL;
374                         spin_lock(&pde->pde_unload_lock);
375                         list_add(&pdeo->lh, &pde->pde_openers);
376                         spin_unlock(&pde->pde_unload_lock);
377                 } else
378                         kmem_cache_free(pde_opener_cache, pdeo);
379         }
380 
381 out_unuse:
382         unuse_pde(pde);
383         return rv;
384 }
385 
386 static int proc_reg_release(struct inode *inode, struct file *file)
387 {
388         struct proc_dir_entry *pde = PDE(inode);
389         struct pde_opener *pdeo;
390         spin_lock(&pde->pde_unload_lock);
391         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
392                 if (pdeo->file == file) {
393                         close_pdeo(pde, pdeo);
394                         return 0;
395                 }
396         }
397         spin_unlock(&pde->pde_unload_lock);
398         return 0;
399 }
400 
401 static const struct file_operations proc_reg_file_ops = {
402         .llseek         = proc_reg_llseek,
403         .read           = proc_reg_read,
404         .write          = proc_reg_write,
405         .poll           = proc_reg_poll,
406         .unlocked_ioctl = proc_reg_unlocked_ioctl,
407 #ifdef CONFIG_COMPAT
408         .compat_ioctl   = proc_reg_compat_ioctl,
409 #endif
410         .mmap           = proc_reg_mmap,
411         .get_unmapped_area = proc_reg_get_unmapped_area,
412         .open           = proc_reg_open,
413         .release        = proc_reg_release,
414 };
415 
416 #ifdef CONFIG_COMPAT
417 static const struct file_operations proc_reg_file_ops_no_compat = {
418         .llseek         = proc_reg_llseek,
419         .read           = proc_reg_read,
420         .write          = proc_reg_write,
421         .poll           = proc_reg_poll,
422         .unlocked_ioctl = proc_reg_unlocked_ioctl,
423         .mmap           = proc_reg_mmap,
424         .get_unmapped_area = proc_reg_get_unmapped_area,
425         .open           = proc_reg_open,
426         .release        = proc_reg_release,
427 };
428 #endif
429 
430 static void proc_put_link(void *p)
431 {
432         unuse_pde(p);
433 }
434 
435 static const char *proc_get_link(struct dentry *dentry,
436                                  struct inode *inode,
437                                  struct delayed_call *done)
438 {
439         struct proc_dir_entry *pde = PDE(inode);
440         if (!use_pde(pde))
441                 return ERR_PTR(-EINVAL);
442         set_delayed_call(done, proc_put_link, pde);
443         return pde->data;
444 }
445 
446 const struct inode_operations proc_link_inode_operations = {
447         .get_link       = proc_get_link,
448 };
449 
450 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
451 {
452         struct inode *inode = new_inode_pseudo(sb);
453 
454         if (inode) {
455                 inode->i_ino = de->low_ino;
456                 inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
457                 PROC_I(inode)->pde = de;
458 
459                 if (is_empty_pde(de)) {
460                         make_empty_dir_inode(inode);
461                         return inode;
462                 }
463                 if (de->mode) {
464                         inode->i_mode = de->mode;
465                         inode->i_uid = de->uid;
466                         inode->i_gid = de->gid;
467                 }
468                 if (de->size)
469                         inode->i_size = de->size;
470                 if (de->nlink)
471                         set_nlink(inode, de->nlink);
472                 WARN_ON(!de->proc_iops);
473                 inode->i_op = de->proc_iops;
474                 if (de->proc_fops) {
475                         if (S_ISREG(inode->i_mode)) {
476 #ifdef CONFIG_COMPAT
477                                 if (!de->proc_fops->compat_ioctl)
478                                         inode->i_fop =
479                                                 &proc_reg_file_ops_no_compat;
480                                 else
481 #endif
482                                         inode->i_fop = &proc_reg_file_ops;
483                         } else {
484                                 inode->i_fop = de->proc_fops;
485                         }
486                 }
487         } else
488                pde_put(de);
489         return inode;
490 }
491 
492 int proc_fill_super(struct super_block *s, void *data, int silent)
493 {
494         struct pid_namespace *ns = get_pid_ns(s->s_fs_info);
495         struct inode *root_inode;
496         int ret;
497 
498         if (!proc_parse_options(data, ns))
499                 return -EINVAL;
500 
501         /* User space would break if executables or devices appear on proc */
502         s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;
503         s->s_flags |= SB_NODIRATIME | SB_NOSUID | SB_NOEXEC;
504         s->s_blocksize = 1024;
505         s->s_blocksize_bits = 10;
506         s->s_magic = PROC_SUPER_MAGIC;
507         s->s_op = &proc_sops;
508         s->s_time_gran = 1;
509 
510         /*
511          * procfs isn't actually a stacking filesystem; however, there is
512          * too much magic going on inside it to permit stacking things on
513          * top of it
514          */
515         s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH;
516         
517         pde_get(&proc_root);
518         root_inode = proc_get_inode(s, &proc_root);
519         if (!root_inode) {
520                 pr_err("proc_fill_super: get root inode failed\n");
521                 return -ENOMEM;
522         }
523 
524         s->s_root = d_make_root(root_inode);
525         if (!s->s_root) {
526                 pr_err("proc_fill_super: allocate dentry failed\n");
527                 return -ENOMEM;
528         }
529 
530         ret = proc_setup_self(s);
531         if (ret) {
532                 return ret;
533         }
534         return proc_setup_thread_self(s);
535 }
536 

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