fs/proc/inode.c

   1 /*
   2  *  linux/fs/proc/inode.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/time.h>
   8 #include <linux/proc_fs.h>
   9 #include <linux/kernel.h>
  10 #include <linux/mm.h>
  11 #include <linux/string.h>
  12 #include <linux/stat.h>
  13 #include <linux/completion.h>
  14 #include <linux/poll.h>
  15 #include <linux/file.h>
  16 #include <linux/limits.h>
  17 #include <linux/init.h>
  18 #include <linux/module.h>
  19 #include <linux/smp_lock.h>
  20 #include <linux/sysctl.h>
  21
  22 #include <asm/system.h>
  23 #include <asm/uaccess.h>
  24
  25 #include "internal.h"
  26
  27 struct proc_dir_entry *de_get(struct proc_dir_entry *de)
  28 {
  29         atomic_inc(&de->count);
  30         return de;
  31 }
  32
  33 /*
  34  * Decrements the use count and checks for deferred deletion.
  35  */
  36 void de_put(struct proc_dir_entry *de)
  37 {
  38         if (!atomic_read(&de->count)) {
  39                 printk("de_put: entry %s already free!\n", de->name);
  40                 return;
  41         }
  42
  43         if (atomic_dec_and_test(&de->count))
  44                 free_proc_entry(de);
  45 }
  46
  47 /*
  48  * Decrement the use count of the proc_dir_entry.
  49  */
  50 static void proc_delete_inode(struct inode *inode)
  51 {
  52         struct proc_dir_entry *de;
  53
  54         truncate_inode_pages(&inode->i_data, 0);
  55
  56         /* Stop tracking associated processes */
  57         put_pid(PROC_I(inode)->pid);
  58
  59         /* Let go of any associated proc directory entry */
  60         de = PROC_I(inode)->pde;
  61         if (de)
  62                 de_put(de);
  63         if (PROC_I(inode)->sysctl)
  64                 sysctl_head_put(PROC_I(inode)->sysctl);
  65         clear_inode(inode);
  66 }
  67
  68 struct vfsmount *proc_mnt;
  69
  70 static struct kmem_cache * proc_inode_cachep;
  71
  72 static struct inode *proc_alloc_inode(struct super_block *sb)
  73 {
  74         struct proc_inode *ei;
  75         struct inode *inode;
  76
  77         ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  78         if (!ei)
  79                 return NULL;
  80         ei->pid = NULL;
  81         ei->fd = 0;
  82         ei->op.proc_get_link = NULL;
  83         ei->pde = NULL;
  84         ei->sysctl = NULL;
  85         ei->sysctl_entry = NULL;
  86         inode = &ei->vfs_inode;
  87         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  88         return inode;
  89 }
  90
  91 static void proc_destroy_inode(struct inode *inode)
  92 {
  93         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  94 }
  95
  96 static void init_once(void *foo)
  97 {
  98         struct proc_inode *ei = (struct proc_inode *) foo;
  99
 100         inode_init_once(&ei->vfs_inode);
 101 }
 102
 103 void __init proc_init_inodecache(void)
 104 {
 105         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
 106                                              sizeof(struct proc_inode),
 107                                              0, (SLAB_RECLAIM_ACCOUNT|
 108                                                 SLAB_MEM_SPREAD|SLAB_PANIC),
 109                                              init_once);
 110 }
 111
 112 static const struct super_operations proc_sops = {
 113         .alloc_inode    = proc_alloc_inode,
 114         .destroy_inode  = proc_destroy_inode,
 115         .drop_inode     = generic_delete_inode,
 116         .delete_inode   = proc_delete_inode,
 117         .statfs         = simple_statfs,
 118 };
 119
 120 static void __pde_users_dec(struct proc_dir_entry *pde)
 121 {
 122         pde->pde_users--;
 123         if (pde->pde_unload_completion && pde->pde_users == 0)
 124                 complete(pde->pde_unload_completion);
 125 }
 126
 127 void pde_users_dec(struct proc_dir_entry *pde)
 128 {
 129         spin_lock(&pde->pde_unload_lock);
 130         __pde_users_dec(pde);
 131         spin_unlock(&pde->pde_unload_lock);
 132 }
 133
 134 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 135 {
 136         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 137         loff_t rv = -EINVAL;
 138         loff_t (*llseek)(struct file *, loff_t, int);
 139
 140         spin_lock(&pde->pde_unload_lock);
 141         /*
 142          * remove_proc_entry() is going to delete PDE (as part of module
 143          * cleanup sequence). No new callers into module allowed.
 144          */
 145         if (!pde->proc_fops) {
 146                 spin_unlock(&pde->pde_unload_lock);
 147                 return rv;
 148         }
 149         /*
 150          * Bump refcount so that remove_proc_entry will wail for ->llseek to
 151          * complete.
 152          */
 153         pde->pde_users++;
 154         /*
 155          * Save function pointer under lock, to protect against ->proc_fops
 156          * NULL'ifying right after ->pde_unload_lock is dropped.
 157          */
 158         llseek = pde->proc_fops->llseek;
 159         spin_unlock(&pde->pde_unload_lock);
 160
 161         if (!llseek)
 162                 llseek = default_llseek;
 163         rv = llseek(file, offset, whence);
 164
 165         pde_users_dec(pde);
 166         return rv;
 167 }
 168
 169 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 170 {
 171         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 172         ssize_t rv = -EIO;
 173         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 174
 175         spin_lock(&pde->pde_unload_lock);
 176         if (!pde->proc_fops) {
 177                 spin_unlock(&pde->pde_unload_lock);
 178                 return rv;
 179         }
 180         pde->pde_users++;
 181         read = pde->proc_fops->read;
 182         spin_unlock(&pde->pde_unload_lock);
 183
 184         if (read)
 185                 rv = read(file, buf, count, ppos);
 186
 187         pde_users_dec(pde);
 188         return rv;
 189 }
 190
 191 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 192 {
 193         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 194         ssize_t rv = -EIO;
 195         ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 196
 197         spin_lock(&pde->pde_unload_lock);
 198         if (!pde->proc_fops) {
 199                 spin_unlock(&pde->pde_unload_lock);
 200                 return rv;
 201         }
 202         pde->pde_users++;
 203         write = pde->proc_fops->write;
 204         spin_unlock(&pde->pde_unload_lock);
 205
 206         if (write)
 207                 rv = write(file, buf, count, ppos);
 208
 209         pde_users_dec(pde);
 210         return rv;
 211 }
 212
 213 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 214 {
 215         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 216         unsigned int rv = DEFAULT_POLLMASK;
 217         unsigned int (*poll)(struct file *, struct poll_table_struct *);
 218
 219         spin_lock(&pde->pde_unload_lock);
 220         if (!pde->proc_fops) {
 221                 spin_unlock(&pde->pde_unload_lock);
 222                 return rv;
 223         }
 224         pde->pde_users++;
 225         poll = pde->proc_fops->poll;
 226         spin_unlock(&pde->pde_unload_lock);
 227
 228         if (poll)
 229                 rv = poll(file, pts);
 230
 231         pde_users_dec(pde);
 232         return rv;
 233 }
 234
 235 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 236 {
 237         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 238         long rv = -ENOTTY;
 239         long (*unlocked_ioctl)(struct file *, unsigned int, unsigned long);
 240         int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
 241
 242         spin_lock(&pde->pde_unload_lock);
 243         if (!pde->proc_fops) {
 244                 spin_unlock(&pde->pde_unload_lock);
 245                 return rv;
 246         }
 247         pde->pde_users++;
 248         unlocked_ioctl = pde->proc_fops->unlocked_ioctl;
 249         ioctl = pde->proc_fops->ioctl;
 250         spin_unlock(&pde->pde_unload_lock);
 251
 252         if (unlocked_ioctl) {
 253                 rv = unlocked_ioctl(file, cmd, arg);
 254                 if (rv == -ENOIOCTLCMD)
 255                         rv = -EINVAL;
 256         } else if (ioctl) {
 257                 lock_kernel();
 258                 rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg);
 259                 unlock_kernel();
 260         }
 261
 262         pde_users_dec(pde);
 263         return rv;
 264 }
 265
 266 #ifdef CONFIG_COMPAT
 267 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 268 {
 269         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 270         long rv = -ENOTTY;
 271         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 272
 273         spin_lock(&pde->pde_unload_lock);
 274         if (!pde->proc_fops) {
 275                 spin_unlock(&pde->pde_unload_lock);
 276                 return rv;
 277         }
 278         pde->pde_users++;
 279         compat_ioctl = pde->proc_fops->compat_ioctl;
 280         spin_unlock(&pde->pde_unload_lock);
 281
 282         if (compat_ioctl)
 283                 rv = compat_ioctl(file, cmd, arg);
 284
 285         pde_users_dec(pde);
 286         return rv;
 287 }
 288 #endif
 289
 290 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 291 {
 292         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 293         int rv = -EIO;
 294         int (*mmap)(struct file *, struct vm_area_struct *);
 295
 296         spin_lock(&pde->pde_unload_lock);
 297         if (!pde->proc_fops) {
 298                 spin_unlock(&pde->pde_unload_lock);
 299                 return rv;
 300         }
 301         pde->pde_users++;
 302         mmap = pde->proc_fops->mmap;
 303         spin_unlock(&pde->pde_unload_lock);
 304
 305         if (mmap)
 306                 rv = mmap(file, vma);
 307
 308         pde_users_dec(pde);
 309         return rv;
 310 }
 311
 312 static int proc_reg_open(struct inode *inode, struct file *file)
 313 {
 314         struct proc_dir_entry *pde = PDE(inode);
 315         int rv = 0;
 316         int (*open)(struct inode *, struct file *);
 317         int (*release)(struct inode *, struct file *);
 318         struct pde_opener *pdeo;
 319
 320         /*
 321          * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 322          * sequence. ->release won't be called because ->proc_fops will be
 323          * cleared. Depending on complexity of ->release, consequences vary.
 324          *
 325          * We can't wait for mercy when close will be done for real, it's
 326          * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 327          * by hand in remove_proc_entry(). For this, save opener's credentials
 328          * for later.
 329          */
 330         pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 331         if (!pdeo)
 332                 return -ENOMEM;
 333
 334         spin_lock(&pde->pde_unload_lock);
 335         if (!pde->proc_fops) {
 336                 spin_unlock(&pde->pde_unload_lock);
 337                 kfree(pdeo);
 338                 return -EINVAL;
 339         }
 340         pde->pde_users++;
 341         open = pde->proc_fops->open;
 342         release = pde->proc_fops->release;
 343         spin_unlock(&pde->pde_unload_lock);
 344
 345         if (open)
 346                 rv = open(inode, file);
 347
 348         spin_lock(&pde->pde_unload_lock);
 349         if (rv == 0 && release) {
 350                 /* To know what to release. */
 351                 pdeo->inode = inode;
 352                 pdeo->file = file;
 353                 /* Strictly for "too late" ->release in proc_reg_release(). */
 354                 pdeo->release = release;
 355                 list_add(&pdeo->lh, &pde->pde_openers);
 356         } else
 357                 kfree(pdeo);
 358         __pde_users_dec(pde);
 359         spin_unlock(&pde->pde_unload_lock);
 360         return rv;
 361 }
 362
 363 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 364                                         struct inode *inode, struct file *file)
 365 {
 366         struct pde_opener *pdeo;
 367
 368         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 369                 if (pdeo->inode == inode && pdeo->file == file)
 370                         return pdeo;
 371         }
 372         return NULL;
 373 }
 374
 375 static int proc_reg_release(struct inode *inode, struct file *file)
 376 {
 377         struct proc_dir_entry *pde = PDE(inode);
 378         int rv = 0;
 379         int (*release)(struct inode *, struct file *);
 380         struct pde_opener *pdeo;
 381
 382         spin_lock(&pde->pde_unload_lock);
 383         pdeo = find_pde_opener(pde, inode, file);
 384         if (!pde->proc_fops) {
 385                 /*
 386                  * Can't simply exit, __fput() will think that everything is OK,
 387                  * and move on to freeing struct file. remove_proc_entry() will
 388                  * find slacker in opener's list and will try to do non-trivial
 389                  * things with struct file. Therefore, remove opener from list.
 390                  *
 391                  * But if opener is removed from list, who will ->release it?
 392                  */
 393                 if (pdeo) {
 394                         list_del(&pdeo->lh);
 395                         spin_unlock(&pde->pde_unload_lock);
 396                         rv = pdeo->release(inode, file);
 397                         kfree(pdeo);
 398                 } else
 399                         spin_unlock(&pde->pde_unload_lock);
 400                 return rv;
 401         }
 402         pde->pde_users++;
 403         release = pde->proc_fops->release;
 404         if (pdeo) {
 405                 list_del(&pdeo->lh);
 406                 kfree(pdeo);
 407         }
 408         spin_unlock(&pde->pde_unload_lock);
 409
 410         if (release)
 411                 rv = release(inode, file);
 412
 413         pde_users_dec(pde);
 414         return rv;
 415 }
 416
 417 static const struct file_operations proc_reg_file_ops = {
 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 #ifdef CONFIG_COMPAT
 424         .compat_ioctl   = proc_reg_compat_ioctl,
 425 #endif
 426         .mmap           = proc_reg_mmap,
 427         .open           = proc_reg_open,
 428         .release        = proc_reg_release,
 429 };
 430
 431 #ifdef CONFIG_COMPAT
 432 static const struct file_operations proc_reg_file_ops_no_compat = {
 433         .llseek         = proc_reg_llseek,
 434         .read           = proc_reg_read,
 435         .write          = proc_reg_write,
 436         .poll           = proc_reg_poll,
 437         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 438         .mmap           = proc_reg_mmap,
 439         .open           = proc_reg_open,
 440         .release        = proc_reg_release,
 441 };
 442 #endif
 443
 444 struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
 445                                 struct proc_dir_entry *de)
 446 {
 447         struct inode * inode;
 448
 449         inode = iget_locked(sb, ino);
 450         if (!inode)
 451                 return NULL;
 452         if (inode->i_state & I_NEW) {
 453                 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 454                 PROC_I(inode)->fd = 0;
 455                 PROC_I(inode)->pde = de;
 456
 457                 if (de->mode) {
 458                         inode->i_mode = de->mode;
 459                         inode->i_uid = de->uid;
 460                         inode->i_gid = de->gid;
 461                 }
 462                 if (de->size)
 463                         inode->i_size = de->size;
 464                 if (de->nlink)
 465                         inode->i_nlink = de->nlink;
 466                 if (de->proc_iops)
 467                         inode->i_op = de->proc_iops;
 468                 if (de->proc_fops) {
 469                         if (S_ISREG(inode->i_mode)) {
 470 #ifdef CONFIG_COMPAT
 471                                 if (!de->proc_fops->compat_ioctl)
 472                                         inode->i_fop =
 473                                                 &proc_reg_file_ops_no_compat;
 474                                 else
 475 #endif
 476                                         inode->i_fop = &proc_reg_file_ops;
 477                         } else {
 478                                 inode->i_fop = de->proc_fops;
 479                         }
 480                 }
 481                 unlock_new_inode(inode);
 482         } else
 483                de_put(de);
 484         return inode;
 485 }
 486
 487 int proc_fill_super(struct super_block *s)
 488 {
 489         struct inode * root_inode;
 490
 491         s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 492         s->s_blocksize = 1024;
 493         s->s_blocksize_bits = 10;
 494         s->s_magic = PROC_SUPER_MAGIC;
 495         s->s_op = &proc_sops;
 496         s->s_time_gran = 1;
 497
 498         de_get(&proc_root);
 499         root_inode = proc_get_inode(s, PROC_ROOT_INO, &proc_root);
 500         if (!root_inode)
 501                 goto out_no_root;
 502         root_inode->i_uid = 0;
 503         root_inode->i_gid = 0;
 504         s->s_root = d_alloc_root(root_inode);
 505         if (!s->s_root)
 506                 goto out_no_root;
 507         return 0;
 508
 509 out_no_root:
 510         printk("proc_read_super: get root inode failed\n");
 511         iput(root_inode);
 512         de_put(&proc_root);
 513         return -ENOMEM;
 514 }