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