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/pid_namespace.h>
  11 #include <linux/mm.h>
  12 #include <linux/string.h>
  13 #include <linux/stat.h>
  14 #include <linux/completion.h>
  15 #include <linux/poll.h>
  16 #include <linux/printk.h>
  17 #include <linux/file.h>
  18 #include <linux/limits.h>
  19 #include <linux/init.h>
  20 #include <linux/module.h>
  21 #include <linux/sysctl.h>
  22 #include <linux/seq_file.h>
  23 #include <linux/slab.h>
  24 #include <linux/mount.h>
  25 #include <linux/magic.h>
  26 #include <linux/namei.h>
  27
  28 #include <asm/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         head = PROC_I(inode)->sysctl;
  48         if (head) {
  49                 RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
  50                 sysctl_head_put(head);
  51         }
  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_ops = NULL;
  71         inode = &ei->vfs_inode;
  72         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  73         return inode;
  74 }
  75
  76 static void proc_i_callback(struct rcu_head *head)
  77 {
  78         struct inode *inode = container_of(head, struct inode, i_rcu);
  79         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  80 }
  81
  82 static void proc_destroy_inode(struct inode *inode)
  83 {
  84         call_rcu(&inode->i_rcu, proc_i_callback);
  85 }
  86
  87 static void init_once(void *foo)
  88 {
  89         struct proc_inode *ei = (struct proc_inode *) foo;
  90
  91         inode_init_once(&ei->vfs_inode);
  92 }
  93
  94 void __init proc_init_inodecache(void)
  95 {
  96         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  97                                              sizeof(struct proc_inode),
  98                                              0, (SLAB_RECLAIM_ACCOUNT|
  99                                                 SLAB_MEM_SPREAD|SLAB_PANIC),
 100                                              init_once);
 101 }
 102
 103 static int proc_show_options(struct seq_file *seq, struct dentry *root)
 104 {
 105         struct super_block *sb = root->d_sb;
 106         struct pid_namespace *pid = sb->s_fs_info;
 107
 108         if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
 109                 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
 110         if (pid->hide_pid != 0)
 111                 seq_printf(seq, ",hidepid=%u", pid->hide_pid);
 112
 113         return 0;
 114 }
 115
 116 static const struct super_operations proc_sops = {
 117         .alloc_inode    = proc_alloc_inode,
 118         .destroy_inode  = proc_destroy_inode,
 119         .drop_inode     = generic_delete_inode,
 120         .evict_inode    = proc_evict_inode,
 121         .statfs         = simple_statfs,
 122         .remount_fs     = proc_remount,
 123         .show_options   = proc_show_options,
 124 };
 125
 126 enum {BIAS = -1U<<31};
 127
 128 static inline int use_pde(struct proc_dir_entry *pde)
 129 {
 130         return atomic_inc_unless_negative(&pde->in_use);
 131 }
 132
 133 static void unuse_pde(struct proc_dir_entry *pde)
 134 {
 135         if (atomic_dec_return(&pde->in_use) == BIAS)
 136                 complete(pde->pde_unload_completion);
 137 }
 138
 139 /* pde is locked */
 140 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
 141 {
 142         if (pdeo->closing) {
 143                 /* somebody else is doing that, just wait */
 144                 DECLARE_COMPLETION_ONSTACK(c);
 145                 pdeo->c = &c;
 146                 spin_unlock(&pde->pde_unload_lock);
 147                 wait_for_completion(&c);
 148                 spin_lock(&pde->pde_unload_lock);
 149         } else {
 150                 struct file *file;
 151                 pdeo->closing = 1;
 152                 spin_unlock(&pde->pde_unload_lock);
 153                 file = pdeo->file;
 154                 pde->proc_fops->release(file_inode(file), file);
 155                 spin_lock(&pde->pde_unload_lock);
 156                 list_del_init(&pdeo->lh);
 157                 if (pdeo->c)
 158                         complete(pdeo->c);
 159                 kfree(pdeo);
 160         }
 161 }
 162
 163 void proc_entry_rundown(struct proc_dir_entry *de)
 164 {
 165         DECLARE_COMPLETION_ONSTACK(c);
 166         /* Wait until all existing callers into module are done. */
 167         de->pde_unload_completion = &c;
 168         if (atomic_add_return(BIAS, &de->in_use) != BIAS)
 169                 wait_for_completion(&c);
 170
 171         spin_lock(&de->pde_unload_lock);
 172         while (!list_empty(&de->pde_openers)) {
 173                 struct pde_opener *pdeo;
 174                 pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
 175                 close_pdeo(de, pdeo);
 176         }
 177         spin_unlock(&de->pde_unload_lock);
 178 }
 179
 180 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 181 {
 182         struct proc_dir_entry *pde = PDE(file_inode(file));
 183         loff_t rv = -EINVAL;
 184         if (use_pde(pde)) {
 185                 loff_t (*llseek)(struct file *, loff_t, int);
 186                 llseek = pde->proc_fops->llseek;
 187                 if (!llseek)
 188                         llseek = default_llseek;
 189                 rv = llseek(file, offset, whence);
 190                 unuse_pde(pde);
 191         }
 192         return rv;
 193 }
 194
 195 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 196 {
 197         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 198         struct proc_dir_entry *pde = PDE(file_inode(file));
 199         ssize_t rv = -EIO;
 200         if (use_pde(pde)) {
 201                 read = pde->proc_fops->read;
 202                 if (read)
 203                         rv = read(file, buf, count, ppos);
 204                 unuse_pde(pde);
 205         }
 206         return rv;
 207 }
 208
 209 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 210 {
 211         ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 212         struct proc_dir_entry *pde = PDE(file_inode(file));
 213         ssize_t rv = -EIO;
 214         if (use_pde(pde)) {
 215                 write = pde->proc_fops->write;
 216                 if (write)
 217                         rv = write(file, buf, count, ppos);
 218                 unuse_pde(pde);
 219         }
 220         return rv;
 221 }
 222
 223 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 224 {
 225         struct proc_dir_entry *pde = PDE(file_inode(file));
 226         unsigned int rv = DEFAULT_POLLMASK;
 227         unsigned int (*poll)(struct file *, struct poll_table_struct *);
 228         if (use_pde(pde)) {
 229                 poll = pde->proc_fops->poll;
 230                 if (poll)
 231                         rv = poll(file, pts);
 232                 unuse_pde(pde);
 233         }
 234         return rv;
 235 }
 236
 237 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 238 {
 239         struct proc_dir_entry *pde = PDE(file_inode(file));
 240         long rv = -ENOTTY;
 241         long (*ioctl)(struct file *, unsigned int, unsigned long);
 242         if (use_pde(pde)) {
 243                 ioctl = pde->proc_fops->unlocked_ioctl;
 244                 if (ioctl)
 245                         rv = ioctl(file, cmd, arg);
 246                 unuse_pde(pde);
 247         }
 248         return rv;
 249 }
 250
 251 #ifdef CONFIG_COMPAT
 252 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 253 {
 254         struct proc_dir_entry *pde = PDE(file_inode(file));
 255         long rv = -ENOTTY;
 256         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 257         if (use_pde(pde)) {
 258                 compat_ioctl = pde->proc_fops->compat_ioctl;
 259                 if (compat_ioctl)
 260                         rv = compat_ioctl(file, cmd, arg);
 261                 unuse_pde(pde);
 262         }
 263         return rv;
 264 }
 265 #endif
 266
 267 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 268 {
 269         struct proc_dir_entry *pde = PDE(file_inode(file));
 270         int rv = -EIO;
 271         int (*mmap)(struct file *, struct vm_area_struct *);
 272         if (use_pde(pde)) {
 273                 mmap = pde->proc_fops->mmap;
 274                 if (mmap)
 275                         rv = mmap(file, vma);
 276                 unuse_pde(pde);
 277         }
 278         return rv;
 279 }
 280
 281 static unsigned long
 282 proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,
 283                            unsigned long len, unsigned long pgoff,
 284                            unsigned long flags)
 285 {
 286         struct proc_dir_entry *pde = PDE(file_inode(file));
 287         unsigned long rv = -EIO;
 288
 289         if (use_pde(pde)) {
 290                 typeof(proc_reg_get_unmapped_area) *get_area;
 291
 292                 get_area = pde->proc_fops->get_unmapped_area;
 293 #ifdef CONFIG_MMU
 294                 if (!get_area)
 295                         get_area = current->mm->get_unmapped_area;
 296 #endif
 297
 298                 if (get_area)
 299                         rv = get_area(file, orig_addr, len, pgoff, flags);
 300                 else
 301                         rv = orig_addr;
 302                 unuse_pde(pde);
 303         }
 304         return rv;
 305 }
 306
 307 static int proc_reg_open(struct inode *inode, struct file *file)
 308 {
 309         struct proc_dir_entry *pde = PDE(inode);
 310         int rv = 0;
 311         int (*open)(struct inode *, struct file *);
 312         int (*release)(struct inode *, struct file *);
 313         struct pde_opener *pdeo;
 314
 315         /*
 316          * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 317          * sequence. ->release won't be called because ->proc_fops will be
 318          * cleared. Depending on complexity of ->release, consequences vary.
 319          *
 320          * We can't wait for mercy when close will be done for real, it's
 321          * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 322          * by hand in remove_proc_entry(). For this, save opener's credentials
 323          * for later.
 324          */
 325         pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);
 326         if (!pdeo)
 327                 return -ENOMEM;
 328
 329         if (!use_pde(pde)) {
 330                 kfree(pdeo);
 331                 return -ENOENT;
 332         }
 333         open = pde->proc_fops->open;
 334         release = pde->proc_fops->release;
 335
 336         if (open)
 337                 rv = open(inode, file);
 338
 339         if (rv == 0 && release) {
 340                 /* To know what to release. */
 341                 pdeo->file = file;
 342                 /* Strictly for "too late" ->release in proc_reg_release(). */
 343                 spin_lock(&pde->pde_unload_lock);
 344                 list_add(&pdeo->lh, &pde->pde_openers);
 345                 spin_unlock(&pde->pde_unload_lock);
 346         } else
 347                 kfree(pdeo);
 348
 349         unuse_pde(pde);
 350         return rv;
 351 }
 352
 353 static int proc_reg_release(struct inode *inode, struct file *file)
 354 {
 355         struct proc_dir_entry *pde = PDE(inode);
 356         struct pde_opener *pdeo;
 357         spin_lock(&pde->pde_unload_lock);
 358         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 359                 if (pdeo->file == file) {
 360                         close_pdeo(pde, pdeo);
 361                         break;
 362                 }
 363         }
 364         spin_unlock(&pde->pde_unload_lock);
 365         return 0;
 366 }
 367
 368 static const struct file_operations proc_reg_file_ops = {
 369         .llseek         = proc_reg_llseek,
 370         .read           = proc_reg_read,
 371         .write          = proc_reg_write,
 372         .poll           = proc_reg_poll,
 373         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 374 #ifdef CONFIG_COMPAT
 375         .compat_ioctl   = proc_reg_compat_ioctl,
 376 #endif
 377         .mmap           = proc_reg_mmap,
 378         .get_unmapped_area = proc_reg_get_unmapped_area,
 379         .open           = proc_reg_open,
 380         .release        = proc_reg_release,
 381 };
 382
 383 #ifdef CONFIG_COMPAT
 384 static const struct file_operations proc_reg_file_ops_no_compat = {
 385         .llseek         = proc_reg_llseek,
 386         .read           = proc_reg_read,
 387         .write          = proc_reg_write,
 388         .poll           = proc_reg_poll,
 389         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 390         .mmap           = proc_reg_mmap,
 391         .get_unmapped_area = proc_reg_get_unmapped_area,
 392         .open           = proc_reg_open,
 393         .release        = proc_reg_release,
 394 };
 395 #endif
 396
 397 static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
 398 {
 399         struct proc_dir_entry *pde = PDE(dentry->d_inode);
 400         if (unlikely(!use_pde(pde)))
 401                 return ERR_PTR(-EINVAL);
 402         nd_set_link(nd, pde->data);
 403         return pde;
 404 }
 405
 406 static void proc_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
 407 {
 408         unuse_pde(p);
 409 }
 410
 411 const struct inode_operations proc_link_inode_operations = {
 412         .readlink       = generic_readlink,
 413         .follow_link    = proc_follow_link,
 414         .put_link       = proc_put_link,
 415 };
 416
 417 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 418 {
 419         struct inode *inode = new_inode_pseudo(sb);
 420
 421         if (inode) {
 422                 inode->i_ino = de->low_ino;
 423                 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 424                 PROC_I(inode)->pde = de;
 425
 426                 if (de->mode) {
 427                         inode->i_mode = de->mode;
 428                         inode->i_uid = de->uid;
 429                         inode->i_gid = de->gid;
 430                 }
 431                 if (de->size)
 432                         inode->i_size = de->size;
 433                 if (de->nlink)
 434                         set_nlink(inode, de->nlink);
 435                 WARN_ON(!de->proc_iops);
 436                 inode->i_op = de->proc_iops;
 437                 if (de->proc_fops) {
 438                         if (S_ISREG(inode->i_mode)) {
 439 #ifdef CONFIG_COMPAT
 440                                 if (!de->proc_fops->compat_ioctl)
 441                                         inode->i_fop =
 442                                                 &proc_reg_file_ops_no_compat;
 443                                 else
 444 #endif
 445                                         inode->i_fop = &proc_reg_file_ops;
 446                         } else {
 447                                 inode->i_fop = de->proc_fops;
 448                         }
 449                 }
 450         } else
 451                pde_put(de);
 452         return inode;
 453 }
 454
 455 int proc_fill_super(struct super_block *s)
 456 {
 457         struct inode *root_inode;
 458         int ret;
 459
 460         s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 461         s->s_blocksize = 1024;
 462         s->s_blocksize_bits = 10;
 463         s->s_magic = PROC_SUPER_MAGIC;
 464         s->s_op = &proc_sops;
 465         s->s_time_gran = 1;
 466
 467         pde_get(&proc_root);
 468         root_inode = proc_get_inode(s, &proc_root);
 469         if (!root_inode) {
 470                 pr_err("proc_fill_super: get root inode failed\n");
 471                 return -ENOMEM;
 472         }
 473
 474         s->s_root = d_make_root(root_inode);
 475         if (!s->s_root) {
 476                 pr_err("proc_fill_super: allocate dentry failed\n");
 477                 return -ENOMEM;
 478         }
 479
 480         ret = proc_setup_self(s);
 481         if (ret) {
 482                 return ret;
 483         }
 484         return proc_setup_thread_self(s);
 485 }