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 #include <linux/slab.h>
  22
  23 #include <asm/system.h>
  24 #include <asm/uaccess.h>
  25
  26 #include "internal.h"
  27
  28 static void proc_delete_inode(struct inode *inode)
  29 {
  30         struct proc_dir_entry *de;
  31
  32         truncate_inode_pages(&inode->i_data, 0);
  33
  34         /* Stop tracking associated processes */
  35         put_pid(PROC_I(inode)->pid);
  36
  37         /* Let go of any associated proc directory entry */
  38         de = PROC_I(inode)->pde;
  39         if (de)
  40                 pde_put(de);
  41         if (PROC_I(inode)->sysctl)
  42                 sysctl_head_put(PROC_I(inode)->sysctl);
  43         clear_inode(inode);
  44 }
  45
  46 struct vfsmount *proc_mnt;
  47
  48 static struct kmem_cache * proc_inode_cachep;
  49
  50 static struct inode *proc_alloc_inode(struct super_block *sb)
  51 {
  52         struct proc_inode *ei;
  53         struct inode *inode;
  54
  55         ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  56         if (!ei)
  57                 return NULL;
  58         ei->pid = NULL;
  59         ei->fd = 0;
  60         ei->op.proc_get_link = NULL;
  61         ei->pde = NULL;
  62         ei->sysctl = NULL;
  63         ei->sysctl_entry = NULL;
  64         inode = &ei->vfs_inode;
  65         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  66         return inode;
  67 }
  68
  69 static void proc_destroy_inode(struct inode *inode)
  70 {
  71         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  72 }
  73
  74 static void init_once(void *foo)
  75 {
  76         struct proc_inode *ei = (struct proc_inode *) foo;
  77
  78         inode_init_once(&ei->vfs_inode);
  79 }
  80
  81 void __init proc_init_inodecache(void)
  82 {
  83         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  84                                              sizeof(struct proc_inode),
  85                                              0, (SLAB_RECLAIM_ACCOUNT|
  86                                                 SLAB_MEM_SPREAD|SLAB_PANIC),
  87                                              init_once);
  88 }
  89
  90 static const struct super_operations proc_sops = {
  91         .alloc_inode    = proc_alloc_inode,
  92         .destroy_inode  = proc_destroy_inode,
  93         .drop_inode     = generic_delete_inode,
  94         .delete_inode   = proc_delete_inode,
  95         .statfs         = simple_statfs,
  96 };
  97
  98 static void __pde_users_dec(struct proc_dir_entry *pde)
  99 {
 100         pde->pde_users--;
 101         if (pde->pde_unload_completion && pde->pde_users == 0)
 102                 complete(pde->pde_unload_completion);
 103 }
 104
 105 void pde_users_dec(struct proc_dir_entry *pde)
 106 {
 107         spin_lock(&pde->pde_unload_lock);
 108         __pde_users_dec(pde);
 109         spin_unlock(&pde->pde_unload_lock);
 110 }
 111
 112 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 113 {
 114         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 115         loff_t rv = -EINVAL;
 116         loff_t (*llseek)(struct file *, loff_t, int);
 117
 118         spin_lock(&pde->pde_unload_lock);
 119         /*
 120          * remove_proc_entry() is going to delete PDE (as part of module
 121          * cleanup sequence). No new callers into module allowed.
 122          */
 123         if (!pde->proc_fops) {
 124                 spin_unlock(&pde->pde_unload_lock);
 125                 return rv;
 126         }
 127         /*
 128          * Bump refcount so that remove_proc_entry will wail for ->llseek to
 129          * complete.
 130          */
 131         pde->pde_users++;
 132         /*
 133          * Save function pointer under lock, to protect against ->proc_fops
 134          * NULL'ifying right after ->pde_unload_lock is dropped.
 135          */
 136         llseek = pde->proc_fops->llseek;
 137         spin_unlock(&pde->pde_unload_lock);
 138
 139         if (!llseek)
 140                 llseek = default_llseek;
 141         rv = llseek(file, offset, whence);
 142
 143         pde_users_dec(pde);
 144         return rv;
 145 }
 146
 147 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 148 {
 149         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 150         ssize_t rv = -EIO;
 151         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 152
 153         spin_lock(&pde->pde_unload_lock);
 154         if (!pde->proc_fops) {
 155                 spin_unlock(&pde->pde_unload_lock);
 156                 return rv;
 157         }
 158         pde->pde_users++;
 159         read = pde->proc_fops->read;
 160         spin_unlock(&pde->pde_unload_lock);
 161
 162         if (read)
 163                 rv = read(file, buf, count, ppos);
 164
 165         pde_users_dec(pde);
 166         return rv;
 167 }
 168
 169 static ssize_t proc_reg_write(struct file *file, const 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 (*write)(struct file *, const 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         write = pde->proc_fops->write;
 182         spin_unlock(&pde->pde_unload_lock);
 183
 184         if (write)
 185                 rv = write(file, buf, count, ppos);
 186
 187         pde_users_dec(pde);
 188         return rv;
 189 }
 190
 191 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 192 {
 193         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 194         unsigned int rv = DEFAULT_POLLMASK;
 195         unsigned int (*poll)(struct file *, struct poll_table_struct *);
 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         poll = pde->proc_fops->poll;
 204         spin_unlock(&pde->pde_unload_lock);
 205
 206         if (poll)
 207                 rv = poll(file, pts);
 208
 209         pde_users_dec(pde);
 210         return rv;
 211 }
 212
 213 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 214 {
 215         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 216         long rv = -ENOTTY;
 217         long (*unlocked_ioctl)(struct file *, unsigned int, unsigned long);
 218         int (*ioctl)(struct inode *, struct file *, unsigned int, unsigned long);
 219
 220         spin_lock(&pde->pde_unload_lock);
 221         if (!pde->proc_fops) {
 222                 spin_unlock(&pde->pde_unload_lock);
 223                 return rv;
 224         }
 225         pde->pde_users++;
 226         unlocked_ioctl = pde->proc_fops->unlocked_ioctl;
 227         ioctl = pde->proc_fops->ioctl;
 228         spin_unlock(&pde->pde_unload_lock);
 229
 230         if (unlocked_ioctl) {
 231                 rv = unlocked_ioctl(file, cmd, arg);
 232                 if (rv == -ENOIOCTLCMD)
 233                         rv = -EINVAL;
 234         } else if (ioctl) {
 235                 WARN_ONCE(1, "Procfs ioctl handlers must use unlocked_ioctl, "
 236                           "%pf will be called without the Bkl held\n", ioctl);
 237                 rv = ioctl(file->f_path.dentry->d_inode, file, cmd, arg);
 238         }
 239
 240         pde_users_dec(pde);
 241         return rv;
 242 }
 243
 244 #ifdef CONFIG_COMPAT
 245 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 246 {
 247         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 248         long rv = -ENOTTY;
 249         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 250
 251         spin_lock(&pde->pde_unload_lock);
 252         if (!pde->proc_fops) {
 253                 spin_unlock(&pde->pde_unload_lock);
 254                 return rv;
 255         }
 256         pde->pde_users++;
 257         compat_ioctl = pde->proc_fops->compat_ioctl;
 258         spin_unlock(&pde->pde_unload_lock);
 259
 260         if (compat_ioctl)
 261                 rv = compat_ioctl(file, cmd, arg);
 262
 263         pde_users_dec(pde);
 264         return rv;
 265 }
 266 #endif
 267
 268 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 269 {
 270         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 271         int rv = -EIO;
 272         int (*mmap)(struct file *, struct vm_area_struct *);
 273
 274         spin_lock(&pde->pde_unload_lock);
 275         if (!pde->proc_fops) {
 276                 spin_unlock(&pde->pde_unload_lock);
 277                 return rv;
 278         }
 279         pde->pde_users++;
 280         mmap = pde->proc_fops->mmap;
 281         spin_unlock(&pde->pde_unload_lock);
 282
 283         if (mmap)
 284                 rv = mmap(file, vma);
 285
 286         pde_users_dec(pde);
 287         return rv;
 288 }
 289
 290 static int proc_reg_open(struct inode *inode, struct file *file)
 291 {
 292         struct proc_dir_entry *pde = PDE(inode);
 293         int rv = 0;
 294         int (*open)(struct inode *, struct file *);
 295         int (*release)(struct inode *, struct file *);
 296         struct pde_opener *pdeo;
 297
 298         /*
 299          * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 300          * sequence. ->release won't be called because ->proc_fops will be
 301          * cleared. Depending on complexity of ->release, consequences vary.
 302          *
 303          * We can't wait for mercy when close will be done for real, it's
 304          * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 305          * by hand in remove_proc_entry(). For this, save opener's credentials
 306          * for later.
 307          */
 308         pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 309         if (!pdeo)
 310                 return -ENOMEM;
 311
 312         spin_lock(&pde->pde_unload_lock);
 313         if (!pde->proc_fops) {
 314                 spin_unlock(&pde->pde_unload_lock);
 315                 kfree(pdeo);
 316                 return -EINVAL;
 317         }
 318         pde->pde_users++;
 319         open = pde->proc_fops->open;
 320         release = pde->proc_fops->release;
 321         spin_unlock(&pde->pde_unload_lock);
 322
 323         if (open)
 324                 rv = open(inode, file);
 325
 326         spin_lock(&pde->pde_unload_lock);
 327         if (rv == 0 && release) {
 328                 /* To know what to release. */
 329                 pdeo->inode = inode;
 330                 pdeo->file = file;
 331                 /* Strictly for "too late" ->release in proc_reg_release(). */
 332                 pdeo->release = release;
 333                 list_add(&pdeo->lh, &pde->pde_openers);
 334         } else
 335                 kfree(pdeo);
 336         __pde_users_dec(pde);
 337         spin_unlock(&pde->pde_unload_lock);
 338         return rv;
 339 }
 340
 341 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 342                                         struct inode *inode, struct file *file)
 343 {
 344         struct pde_opener *pdeo;
 345
 346         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 347                 if (pdeo->inode == inode && pdeo->file == file)
 348                         return pdeo;
 349         }
 350         return NULL;
 351 }
 352
 353 static int proc_reg_release(struct inode *inode, struct file *file)
 354 {
 355         struct proc_dir_entry *pde = PDE(inode);
 356         int rv = 0;
 357         int (*release)(struct inode *, struct file *);
 358         struct pde_opener *pdeo;
 359
 360         spin_lock(&pde->pde_unload_lock);
 361         pdeo = find_pde_opener(pde, inode, file);
 362         if (!pde->proc_fops) {
 363                 /*
 364                  * Can't simply exit, __fput() will think that everything is OK,
 365                  * and move on to freeing struct file. remove_proc_entry() will
 366                  * find slacker in opener's list and will try to do non-trivial
 367                  * things with struct file. Therefore, remove opener from list.
 368                  *
 369                  * But if opener is removed from list, who will ->release it?
 370                  */
 371                 if (pdeo) {
 372                         list_del(&pdeo->lh);
 373                         spin_unlock(&pde->pde_unload_lock);
 374                         rv = pdeo->release(inode, file);
 375                         kfree(pdeo);
 376                 } else
 377                         spin_unlock(&pde->pde_unload_lock);
 378                 return rv;
 379         }
 380         pde->pde_users++;
 381         release = pde->proc_fops->release;
 382         if (pdeo) {
 383                 list_del(&pdeo->lh);
 384                 kfree(pdeo);
 385         }
 386         spin_unlock(&pde->pde_unload_lock);
 387
 388         if (release)
 389                 rv = release(inode, file);
 390
 391         pde_users_dec(pde);
 392         return rv;
 393 }
 394
 395 static const struct file_operations proc_reg_file_ops = {
 396         .llseek         = proc_reg_llseek,
 397         .read           = proc_reg_read,
 398         .write          = proc_reg_write,
 399         .poll           = proc_reg_poll,
 400         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 401 #ifdef CONFIG_COMPAT
 402         .compat_ioctl   = proc_reg_compat_ioctl,
 403 #endif
 404         .mmap           = proc_reg_mmap,
 405         .open           = proc_reg_open,
 406         .release        = proc_reg_release,
 407 };
 408
 409 #ifdef CONFIG_COMPAT
 410 static const struct file_operations proc_reg_file_ops_no_compat = {
 411         .llseek         = proc_reg_llseek,
 412         .read           = proc_reg_read,
 413         .write          = proc_reg_write,
 414         .poll           = proc_reg_poll,
 415         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 416         .mmap           = proc_reg_mmap,
 417         .open           = proc_reg_open,
 418         .release        = proc_reg_release,
 419 };
 420 #endif
 421
 422 struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
 423                                 struct proc_dir_entry *de)
 424 {
 425         struct inode * inode;
 426
 427         inode = iget_locked(sb, ino);
 428         if (!inode)
 429                 return NULL;
 430         if (inode->i_state & I_NEW) {
 431                 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 432                 PROC_I(inode)->fd = 0;
 433                 PROC_I(inode)->pde = de;
 434
 435                 if (de->mode) {
 436                         inode->i_mode = de->mode;
 437                         inode->i_uid = de->uid;
 438                         inode->i_gid = de->gid;
 439                 }
 440                 if (de->size)
 441                         inode->i_size = de->size;
 442                 if (de->nlink)
 443                         inode->i_nlink = de->nlink;
 444                 if (de->proc_iops)
 445                         inode->i_op = de->proc_iops;
 446                 if (de->proc_fops) {
 447                         if (S_ISREG(inode->i_mode)) {
 448 #ifdef CONFIG_COMPAT
 449                                 if (!de->proc_fops->compat_ioctl)
 450                                         inode->i_fop =
 451                                                 &proc_reg_file_ops_no_compat;
 452                                 else
 453 #endif
 454                                         inode->i_fop = &proc_reg_file_ops;
 455                         } else {
 456                                 inode->i_fop = de->proc_fops;
 457                         }
 458                 }
 459                 unlock_new_inode(inode);
 460         } else
 461                pde_put(de);
 462         return inode;
 463 }
 464
 465 int proc_fill_super(struct super_block *s)
 466 {
 467         struct inode * root_inode;
 468
 469         s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 470         s->s_blocksize = 1024;
 471         s->s_blocksize_bits = 10;
 472         s->s_magic = PROC_SUPER_MAGIC;
 473         s->s_op = &proc_sops;
 474         s->s_time_gran = 1;
 475
 476         pde_get(&proc_root);
 477         root_inode = proc_get_inode(s, PROC_ROOT_INO, &proc_root);
 478         if (!root_inode)
 479                 goto out_no_root;
 480         root_inode->i_uid = 0;
 481         root_inode->i_gid = 0;
 482         s->s_root = d_alloc_root(root_inode);
 483         if (!s->s_root)
 484                 goto out_no_root;
 485         return 0;
 486
 487 out_no_root:
 488         printk("proc_read_super: get root inode failed\n");
 489         iput(root_inode);
 490         pde_put(&proc_root);
 491         return -ENOMEM;
 492 }