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/sysctl.h>
  20 #include <linux/slab.h>
  21
  22 #include <asm/system.h>
  23 #include <asm/uaccess.h>
  24
  25 #include "internal.h"
  26
  27 static void proc_evict_inode(struct inode *inode)
  28 {
  29         struct proc_dir_entry *de;
  30         struct ctl_table_header *head;
  31
  32         truncate_inode_pages(&inode->i_data, 0);
  33         end_writeback(inode);
  34
  35         /* Stop tracking associated processes */
  36         put_pid(PROC_I(inode)->pid);
  37
  38         /* Let go of any associated proc directory entry */
  39         de = PROC_I(inode)->pde;
  40         if (de)
  41                 pde_put(de);
  42         head = PROC_I(inode)->sysctl;
  43         if (head) {
  44                 rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
  45                 sysctl_head_put(head);
  46         }
  47 }
  48
  49 struct vfsmount *proc_mnt;
  50
  51 static struct kmem_cache * proc_inode_cachep;
  52
  53 static struct inode *proc_alloc_inode(struct super_block *sb)
  54 {
  55         struct proc_inode *ei;
  56         struct inode *inode;
  57
  58         ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  59         if (!ei)
  60                 return NULL;
  61         ei->pid = NULL;
  62         ei->fd = 0;
  63         ei->op.proc_get_link = NULL;
  64         ei->pde = NULL;
  65         ei->sysctl = NULL;
  66         ei->sysctl_entry = NULL;
  67         inode = &ei->vfs_inode;
  68         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  69         return inode;
  70 }
  71
  72 static void proc_i_callback(struct rcu_head *head)
  73 {
  74         struct inode *inode = container_of(head, struct inode, i_rcu);
  75         INIT_LIST_HEAD(&inode->i_dentry);
  76         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  77 }
  78
  79 static void proc_destroy_inode(struct inode *inode)
  80 {
  81         call_rcu(&inode->i_rcu, proc_i_callback);
  82 }
  83
  84 static void init_once(void *foo)
  85 {
  86         struct proc_inode *ei = (struct proc_inode *) foo;
  87
  88         inode_init_once(&ei->vfs_inode);
  89 }
  90
  91 void __init proc_init_inodecache(void)
  92 {
  93         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  94                                              sizeof(struct proc_inode),
  95                                              0, (SLAB_RECLAIM_ACCOUNT|
  96                                                 SLAB_MEM_SPREAD|SLAB_PANIC),
  97                                              init_once);
  98 }
  99
 100 static const struct super_operations proc_sops = {
 101         .alloc_inode    = proc_alloc_inode,
 102         .destroy_inode  = proc_destroy_inode,
 103         .drop_inode     = generic_delete_inode,
 104         .evict_inode    = proc_evict_inode,
 105         .statfs         = simple_statfs,
 106 };
 107
 108 static void __pde_users_dec(struct proc_dir_entry *pde)
 109 {
 110         pde->pde_users--;
 111         if (pde->pde_unload_completion && pde->pde_users == 0)
 112                 complete(pde->pde_unload_completion);
 113 }
 114
 115 void pde_users_dec(struct proc_dir_entry *pde)
 116 {
 117         spin_lock(&pde->pde_unload_lock);
 118         __pde_users_dec(pde);
 119         spin_unlock(&pde->pde_unload_lock);
 120 }
 121
 122 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 123 {
 124         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 125         loff_t rv = -EINVAL;
 126         loff_t (*llseek)(struct file *, loff_t, int);
 127
 128         spin_lock(&pde->pde_unload_lock);
 129         /*
 130          * remove_proc_entry() is going to delete PDE (as part of module
 131          * cleanup sequence). No new callers into module allowed.
 132          */
 133         if (!pde->proc_fops) {
 134                 spin_unlock(&pde->pde_unload_lock);
 135                 return rv;
 136         }
 137         /*
 138          * Bump refcount so that remove_proc_entry will wail for ->llseek to
 139          * complete.
 140          */
 141         pde->pde_users++;
 142         /*
 143          * Save function pointer under lock, to protect against ->proc_fops
 144          * NULL'ifying right after ->pde_unload_lock is dropped.
 145          */
 146         llseek = pde->proc_fops->llseek;
 147         spin_unlock(&pde->pde_unload_lock);
 148
 149         if (!llseek)
 150                 llseek = default_llseek;
 151         rv = llseek(file, offset, whence);
 152
 153         pde_users_dec(pde);
 154         return rv;
 155 }
 156
 157 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 158 {
 159         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 160         ssize_t rv = -EIO;
 161         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 162
 163         spin_lock(&pde->pde_unload_lock);
 164         if (!pde->proc_fops) {
 165                 spin_unlock(&pde->pde_unload_lock);
 166                 return rv;
 167         }
 168         pde->pde_users++;
 169         read = pde->proc_fops->read;
 170         spin_unlock(&pde->pde_unload_lock);
 171
 172         if (read)
 173                 rv = read(file, buf, count, ppos);
 174
 175         pde_users_dec(pde);
 176         return rv;
 177 }
 178
 179 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 180 {
 181         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 182         ssize_t rv = -EIO;
 183         ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 184
 185         spin_lock(&pde->pde_unload_lock);
 186         if (!pde->proc_fops) {
 187                 spin_unlock(&pde->pde_unload_lock);
 188                 return rv;
 189         }
 190         pde->pde_users++;
 191         write = pde->proc_fops->write;
 192         spin_unlock(&pde->pde_unload_lock);
 193
 194         if (write)
 195                 rv = write(file, buf, count, ppos);
 196
 197         pde_users_dec(pde);
 198         return rv;
 199 }
 200
 201 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 202 {
 203         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 204         unsigned int rv = DEFAULT_POLLMASK;
 205         unsigned int (*poll)(struct file *, struct poll_table_struct *);
 206
 207         spin_lock(&pde->pde_unload_lock);
 208         if (!pde->proc_fops) {
 209                 spin_unlock(&pde->pde_unload_lock);
 210                 return rv;
 211         }
 212         pde->pde_users++;
 213         poll = pde->proc_fops->poll;
 214         spin_unlock(&pde->pde_unload_lock);
 215
 216         if (poll)
 217                 rv = poll(file, pts);
 218
 219         pde_users_dec(pde);
 220         return rv;
 221 }
 222
 223 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 224 {
 225         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 226         long rv = -ENOTTY;
 227         long (*ioctl)(struct file *, unsigned int, unsigned long);
 228
 229         spin_lock(&pde->pde_unload_lock);
 230         if (!pde->proc_fops) {
 231                 spin_unlock(&pde->pde_unload_lock);
 232                 return rv;
 233         }
 234         pde->pde_users++;
 235         ioctl = pde->proc_fops->unlocked_ioctl;
 236         spin_unlock(&pde->pde_unload_lock);
 237
 238         if (ioctl)
 239                 rv = ioctl(file, cmd, arg);
 240
 241         pde_users_dec(pde);
 242         return rv;
 243 }
 244
 245 #ifdef CONFIG_COMPAT
 246 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 247 {
 248         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 249         long rv = -ENOTTY;
 250         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 251
 252         spin_lock(&pde->pde_unload_lock);
 253         if (!pde->proc_fops) {
 254                 spin_unlock(&pde->pde_unload_lock);
 255                 return rv;
 256         }
 257         pde->pde_users++;
 258         compat_ioctl = pde->proc_fops->compat_ioctl;
 259         spin_unlock(&pde->pde_unload_lock);
 260
 261         if (compat_ioctl)
 262                 rv = compat_ioctl(file, cmd, arg);
 263
 264         pde_users_dec(pde);
 265         return rv;
 266 }
 267 #endif
 268
 269 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 270 {
 271         struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 272         int rv = -EIO;
 273         int (*mmap)(struct file *, struct vm_area_struct *);
 274
 275         spin_lock(&pde->pde_unload_lock);
 276         if (!pde->proc_fops) {
 277                 spin_unlock(&pde->pde_unload_lock);
 278                 return rv;
 279         }
 280         pde->pde_users++;
 281         mmap = pde->proc_fops->mmap;
 282         spin_unlock(&pde->pde_unload_lock);
 283
 284         if (mmap)
 285                 rv = mmap(file, vma);
 286
 287         pde_users_dec(pde);
 288         return rv;
 289 }
 290
 291 static int proc_reg_open(struct inode *inode, struct file *file)
 292 {
 293         struct proc_dir_entry *pde = PDE(inode);
 294         int rv = 0;
 295         int (*open)(struct inode *, struct file *);
 296         int (*release)(struct inode *, struct file *);
 297         struct pde_opener *pdeo;
 298
 299         /*
 300          * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 301          * sequence. ->release won't be called because ->proc_fops will be
 302          * cleared. Depending on complexity of ->release, consequences vary.
 303          *
 304          * We can't wait for mercy when close will be done for real, it's
 305          * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 306          * by hand in remove_proc_entry(). For this, save opener's credentials
 307          * for later.
 308          */
 309         pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 310         if (!pdeo)
 311                 return -ENOMEM;
 312
 313         spin_lock(&pde->pde_unload_lock);
 314         if (!pde->proc_fops) {
 315                 spin_unlock(&pde->pde_unload_lock);
 316                 kfree(pdeo);
 317                 return -EINVAL;
 318         }
 319         pde->pde_users++;
 320         open = pde->proc_fops->open;
 321         release = pde->proc_fops->release;
 322         spin_unlock(&pde->pde_unload_lock);
 323
 324         if (open)
 325                 rv = open(inode, file);
 326
 327         spin_lock(&pde->pde_unload_lock);
 328         if (rv == 0 && release) {
 329                 /* To know what to release. */
 330                 pdeo->inode = inode;
 331                 pdeo->file = file;
 332                 /* Strictly for "too late" ->release in proc_reg_release(). */
 333                 pdeo->release = release;
 334                 list_add(&pdeo->lh, &pde->pde_openers);
 335         } else
 336                 kfree(pdeo);
 337         __pde_users_dec(pde);
 338         spin_unlock(&pde->pde_unload_lock);
 339         return rv;
 340 }
 341
 342 static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 343                                         struct inode *inode, struct file *file)
 344 {
 345         struct pde_opener *pdeo;
 346
 347         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 348                 if (pdeo->inode == inode && pdeo->file == file)
 349                         return pdeo;
 350         }
 351         return NULL;
 352 }
 353
 354 static int proc_reg_release(struct inode *inode, struct file *file)
 355 {
 356         struct proc_dir_entry *pde = PDE(inode);
 357         int rv = 0;
 358         int (*release)(struct inode *, struct file *);
 359         struct pde_opener *pdeo;
 360
 361         spin_lock(&pde->pde_unload_lock);
 362         pdeo = find_pde_opener(pde, inode, file);
 363         if (!pde->proc_fops) {
 364                 /*
 365                  * Can't simply exit, __fput() will think that everything is OK,
 366                  * and move on to freeing struct file. remove_proc_entry() will
 367                  * find slacker in opener's list and will try to do non-trivial
 368                  * things with struct file. Therefore, remove opener from list.
 369                  *
 370                  * But if opener is removed from list, who will ->release it?
 371                  */
 372                 if (pdeo) {
 373                         list_del(&pdeo->lh);
 374                         spin_unlock(&pde->pde_unload_lock);
 375                         rv = pdeo->release(inode, file);
 376                         kfree(pdeo);
 377                 } else
 378                         spin_unlock(&pde->pde_unload_lock);
 379                 return rv;
 380         }
 381         pde->pde_users++;
 382         release = pde->proc_fops->release;
 383         if (pdeo) {
 384                 list_del(&pdeo->lh);
 385                 kfree(pdeo);
 386         }
 387         spin_unlock(&pde->pde_unload_lock);
 388
 389         if (release)
 390                 rv = release(inode, file);
 391
 392         pde_users_dec(pde);
 393         return rv;
 394 }
 395
 396 static const struct file_operations proc_reg_file_ops = {
 397         .llseek         = proc_reg_llseek,
 398         .read           = proc_reg_read,
 399         .write          = proc_reg_write,
 400         .poll           = proc_reg_poll,
 401         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 402 #ifdef CONFIG_COMPAT
 403         .compat_ioctl   = proc_reg_compat_ioctl,
 404 #endif
 405         .mmap           = proc_reg_mmap,
 406         .open           = proc_reg_open,
 407         .release        = proc_reg_release,
 408 };
 409
 410 #ifdef CONFIG_COMPAT
 411 static const struct file_operations proc_reg_file_ops_no_compat = {
 412         .llseek         = proc_reg_llseek,
 413         .read           = proc_reg_read,
 414         .write          = proc_reg_write,
 415         .poll           = proc_reg_poll,
 416         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 417         .mmap           = proc_reg_mmap,
 418         .open           = proc_reg_open,
 419         .release        = proc_reg_release,
 420 };
 421 #endif
 422
 423 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 424 {
 425         struct inode * inode;
 426
 427         inode = iget_locked(sb, de->low_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);
 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 }