root/fs/proc/inode.c

DEFINITIONS

1. proc_evict_inode
2. proc_alloc_inode
3. proc_free_inode
4. init_once
5. proc_init_kmemcache
6. proc_show_options
7. use_pde
8. unuse_pde
9. close_pdeo
10. proc_entry_rundown
11. proc_reg_llseek
12. proc_reg_read
13. proc_reg_write
14. proc_reg_poll
15. proc_reg_unlocked_ioctl
16. proc_reg_compat_ioctl
17. proc_reg_mmap
18. proc_reg_get_unmapped_area
19. proc_reg_open
20. proc_reg_release
21. proc_put_link
22. proc_get_link
23. proc_get_inode

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