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
  27 #include <asm/uaccess.h>
  28
  29 #include "internal.h"
  30
  31 static void proc_evict_inode(struct inode *inode)
  32 {
  33         struct proc_dir_entry *de;
  34         struct ctl_table_header *head;
  35         const struct proc_ns_operations *ns_ops;
  36         void *ns;
  37
  38         truncate_inode_pages(&inode->i_data, 0);
  39         clear_inode(inode);
  40
  41         /* Stop tracking associated processes */
  42         put_pid(PROC_I(inode)->pid);
  43
  44         /* Let go of any associated proc directory entry */
  45         de = PROC_I(inode)->pde;
  46         if (de)
  47                 pde_put(de);
  48         head = PROC_I(inode)->sysctl;
  49         if (head) {
  50                 rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
  51                 sysctl_head_put(head);
  52         }
  53         /* Release any associated namespace */
  54         ns_ops = PROC_I(inode)->ns.ns_ops;
  55         ns = PROC_I(inode)->ns.ns;
  56         if (ns_ops && ns)
  57                 ns_ops->put(ns);
  58 }
  59
  60 static struct kmem_cache * proc_inode_cachep;
  61
  62 static struct inode *proc_alloc_inode(struct super_block *sb)
  63 {
  64         struct proc_inode *ei;
  65         struct inode *inode;
  66
  67         ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  68         if (!ei)
  69                 return NULL;
  70         ei->pid = NULL;
  71         ei->fd = 0;
  72         ei->op.proc_get_link = NULL;
  73         ei->pde = NULL;
  74         ei->sysctl = NULL;
  75         ei->sysctl_entry = NULL;
  76         ei->ns.ns = NULL;
  77         ei->ns.ns_ops = NULL;
  78         inode = &ei->vfs_inode;
  79         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  80         return inode;
  81 }
  82
  83 static void proc_i_callback(struct rcu_head *head)
  84 {
  85         struct inode *inode = container_of(head, struct inode, i_rcu);
  86         kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  87 }
  88
  89 static void proc_destroy_inode(struct inode *inode)
  90 {
  91         call_rcu(&inode->i_rcu, proc_i_callback);
  92 }
  93
  94 static void init_once(void *foo)
  95 {
  96         struct proc_inode *ei = (struct proc_inode *) foo;
  97
  98         inode_init_once(&ei->vfs_inode);
  99 }
 100
 101 void __init proc_init_inodecache(void)
 102 {
 103         proc_inode_cachep = kmem_cache_create("proc_inode_cache",
 104                                              sizeof(struct proc_inode),
 105                                              0, (SLAB_RECLAIM_ACCOUNT|
 106                                                 SLAB_MEM_SPREAD|SLAB_PANIC),
 107                                              init_once);
 108 }
 109
 110 static int proc_show_options(struct seq_file *seq, struct dentry *root)
 111 {
 112         struct super_block *sb = root->d_sb;
 113         struct pid_namespace *pid = sb->s_fs_info;
 114
 115         if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
 116                 seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
 117         if (pid->hide_pid != 0)
 118                 seq_printf(seq, ",hidepid=%u", pid->hide_pid);
 119
 120         return 0;
 121 }
 122
 123 static const struct super_operations proc_sops = {
 124         .alloc_inode    = proc_alloc_inode,
 125         .destroy_inode  = proc_destroy_inode,
 126         .drop_inode     = generic_delete_inode,
 127         .evict_inode    = proc_evict_inode,
 128         .statfs         = simple_statfs,
 129         .remount_fs     = proc_remount,
 130         .show_options   = proc_show_options,
 131 };
 132
 133 enum {BIAS = -1U<<31};
 134
 135 static inline int use_pde(struct proc_dir_entry *pde)
 136 {
 137         return atomic_inc_unless_negative(&pde->in_use);
 138 }
 139
 140 static void unuse_pde(struct proc_dir_entry *pde)
 141 {
 142         if (atomic_dec_return(&pde->in_use) == BIAS)
 143                 complete(pde->pde_unload_completion);
 144 }
 145
 146 /* pde is locked */
 147 static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo)
 148 {
 149         if (pdeo->closing) {
 150                 /* somebody else is doing that, just wait */
 151                 DECLARE_COMPLETION_ONSTACK(c);
 152                 pdeo->c = &c;
 153                 spin_unlock(&pde->pde_unload_lock);
 154                 wait_for_completion(&c);
 155                 spin_lock(&pde->pde_unload_lock);
 156         } else {
 157                 struct file *file;
 158                 pdeo->closing = 1;
 159                 spin_unlock(&pde->pde_unload_lock);
 160                 file = pdeo->file;
 161                 pde->proc_fops->release(file_inode(file), file);
 162                 spin_lock(&pde->pde_unload_lock);
 163                 list_del_init(&pdeo->lh);
 164                 if (pdeo->c)
 165                         complete(pdeo->c);
 166                 kfree(pdeo);
 167         }
 168 }
 169
 170 void proc_entry_rundown(struct proc_dir_entry *de)
 171 {
 172         DECLARE_COMPLETION_ONSTACK(c);
 173         /* Wait until all existing callers into module are done. */
 174         de->pde_unload_completion = &c;
 175         if (atomic_add_return(BIAS, &de->in_use) != BIAS)
 176                 wait_for_completion(&c);
 177
 178         spin_lock(&de->pde_unload_lock);
 179         while (!list_empty(&de->pde_openers)) {
 180                 struct pde_opener *pdeo;
 181                 pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
 182                 close_pdeo(de, pdeo);
 183         }
 184         spin_unlock(&de->pde_unload_lock);
 185 }
 186
 187 static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 188 {
 189         struct proc_dir_entry *pde = PDE(file_inode(file));
 190         loff_t rv = -EINVAL;
 191         if (use_pde(pde)) {
 192                 loff_t (*llseek)(struct file *, loff_t, int);
 193                 llseek = pde->proc_fops->llseek;
 194                 if (!llseek)
 195                         llseek = default_llseek;
 196                 rv = llseek(file, offset, whence);
 197                 unuse_pde(pde);
 198         }
 199         return rv;
 200 }
 201
 202 static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 203 {
 204         ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 205         struct proc_dir_entry *pde = PDE(file_inode(file));
 206         ssize_t rv = -EIO;
 207         if (use_pde(pde)) {
 208                 read = pde->proc_fops->read;
 209                 if (read)
 210                         rv = read(file, buf, count, ppos);
 211                 unuse_pde(pde);
 212         }
 213         return rv;
 214 }
 215
 216 static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 217 {
 218         ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 219         struct proc_dir_entry *pde = PDE(file_inode(file));
 220         ssize_t rv = -EIO;
 221         if (use_pde(pde)) {
 222                 write = pde->proc_fops->write;
 223                 if (write)
 224                         rv = write(file, buf, count, ppos);
 225                 unuse_pde(pde);
 226         }
 227         return rv;
 228 }
 229
 230 static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 231 {
 232         struct proc_dir_entry *pde = PDE(file_inode(file));
 233         unsigned int rv = DEFAULT_POLLMASK;
 234         unsigned int (*poll)(struct file *, struct poll_table_struct *);
 235         if (use_pde(pde)) {
 236                 poll = pde->proc_fops->poll;
 237                 if (poll)
 238                         rv = poll(file, pts);
 239                 unuse_pde(pde);
 240         }
 241         return rv;
 242 }
 243
 244 static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 245 {
 246         struct proc_dir_entry *pde = PDE(file_inode(file));
 247         long rv = -ENOTTY;
 248         long (*ioctl)(struct file *, unsigned int, unsigned long);
 249         if (use_pde(pde)) {
 250                 ioctl = pde->proc_fops->unlocked_ioctl;
 251                 if (ioctl)
 252                         rv = ioctl(file, cmd, arg);
 253                 unuse_pde(pde);
 254         }
 255         return rv;
 256 }
 257
 258 #ifdef CONFIG_COMPAT
 259 static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 260 {
 261         struct proc_dir_entry *pde = PDE(file_inode(file));
 262         long rv = -ENOTTY;
 263         long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 264         if (use_pde(pde)) {
 265                 compat_ioctl = pde->proc_fops->compat_ioctl;
 266                 if (compat_ioctl)
 267                         rv = compat_ioctl(file, cmd, arg);
 268                 unuse_pde(pde);
 269         }
 270         return rv;
 271 }
 272 #endif
 273
 274 static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 275 {
 276         struct proc_dir_entry *pde = PDE(file_inode(file));
 277         int rv = -EIO;
 278         int (*mmap)(struct file *, struct vm_area_struct *);
 279         if (use_pde(pde)) {
 280                 mmap = pde->proc_fops->mmap;
 281                 if (mmap)
 282                         rv = mmap(file, vma);
 283                 unuse_pde(pde);
 284         }
 285         return rv;
 286 }
 287
 288 static int proc_reg_open(struct inode *inode, struct file *file)
 289 {
 290         struct proc_dir_entry *pde = PDE(inode);
 291         int rv = 0;
 292         int (*open)(struct inode *, struct file *);
 293         int (*release)(struct inode *, struct file *);
 294         struct pde_opener *pdeo;
 295
 296         /*
 297          * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 298          * sequence. ->release won't be called because ->proc_fops will be
 299          * cleared. Depending on complexity of ->release, consequences vary.
 300          *
 301          * We can't wait for mercy when close will be done for real, it's
 302          * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 303          * by hand in remove_proc_entry(). For this, save opener's credentials
 304          * for later.
 305          */
 306         pdeo = kzalloc(sizeof(struct pde_opener), GFP_KERNEL);
 307         if (!pdeo)
 308                 return -ENOMEM;
 309
 310         if (!use_pde(pde)) {
 311                 kfree(pdeo);
 312                 return -ENOENT;
 313         }
 314         open = pde->proc_fops->open;
 315         release = pde->proc_fops->release;
 316
 317         if (open)
 318                 rv = open(inode, file);
 319
 320         if (rv == 0 && release) {
 321                 /* To know what to release. */
 322                 pdeo->file = file;
 323                 /* Strictly for "too late" ->release in proc_reg_release(). */
 324                 spin_lock(&pde->pde_unload_lock);
 325                 list_add(&pdeo->lh, &pde->pde_openers);
 326                 spin_unlock(&pde->pde_unload_lock);
 327         } else
 328                 kfree(pdeo);
 329
 330         unuse_pde(pde);
 331         return rv;
 332 }
 333
 334 static int proc_reg_release(struct inode *inode, struct file *file)
 335 {
 336         struct proc_dir_entry *pde = PDE(inode);
 337         struct pde_opener *pdeo;
 338         spin_lock(&pde->pde_unload_lock);
 339         list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 340                 if (pdeo->file == file) {
 341                         close_pdeo(pde, pdeo);
 342                         break;
 343                 }
 344         }
 345         spin_unlock(&pde->pde_unload_lock);
 346         return 0;
 347 }
 348
 349 static const struct file_operations proc_reg_file_ops = {
 350         .llseek         = proc_reg_llseek,
 351         .read           = proc_reg_read,
 352         .write          = proc_reg_write,
 353         .poll           = proc_reg_poll,
 354         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 355 #ifdef CONFIG_COMPAT
 356         .compat_ioctl   = proc_reg_compat_ioctl,
 357 #endif
 358         .mmap           = proc_reg_mmap,
 359         .open           = proc_reg_open,
 360         .release        = proc_reg_release,
 361 };
 362
 363 #ifdef CONFIG_COMPAT
 364 static const struct file_operations proc_reg_file_ops_no_compat = {
 365         .llseek         = proc_reg_llseek,
 366         .read           = proc_reg_read,
 367         .write          = proc_reg_write,
 368         .poll           = proc_reg_poll,
 369         .unlocked_ioctl = proc_reg_unlocked_ioctl,
 370         .mmap           = proc_reg_mmap,
 371         .open           = proc_reg_open,
 372         .release        = proc_reg_release,
 373 };
 374 #endif
 375
 376 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 377 {
 378         struct inode *inode = new_inode_pseudo(sb);
 379
 380         if (inode) {
 381                 inode->i_ino = de->low_ino;
 382                 inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 383                 PROC_I(inode)->pde = de;
 384
 385                 if (de->mode) {
 386                         inode->i_mode = de->mode;
 387                         inode->i_uid = de->uid;
 388                         inode->i_gid = de->gid;
 389                 }
 390                 if (de->size)
 391                         inode->i_size = de->size;
 392                 if (de->nlink)
 393                         set_nlink(inode, de->nlink);
 394                 WARN_ON(!de->proc_iops);
 395                 inode->i_op = de->proc_iops;
 396                 if (de->proc_fops) {
 397                         if (S_ISREG(inode->i_mode)) {
 398 #ifdef CONFIG_COMPAT
 399                                 if (!de->proc_fops->compat_ioctl)
 400                                         inode->i_fop =
 401                                                 &proc_reg_file_ops_no_compat;
 402                                 else
 403 #endif
 404                                         inode->i_fop = &proc_reg_file_ops;
 405                         } else {
 406                                 inode->i_fop = de->proc_fops;
 407                         }
 408                 }
 409         } else
 410                pde_put(de);
 411         return inode;
 412 }
 413
 414 int proc_fill_super(struct super_block *s)
 415 {
 416         struct inode *root_inode;
 417
 418         s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 419         s->s_blocksize = 1024;
 420         s->s_blocksize_bits = 10;
 421         s->s_magic = PROC_SUPER_MAGIC;
 422         s->s_op = &proc_sops;
 423         s->s_time_gran = 1;
 424
 425         pde_get(&proc_root);
 426         root_inode = proc_get_inode(s, &proc_root);
 427         if (!root_inode) {
 428                 pr_err("proc_fill_super: get root inode failed\n");
 429                 return -ENOMEM;
 430         }
 431
 432         s->s_root = d_make_root(root_inode);
 433         if (!s->s_root) {
 434                 pr_err("proc_fill_super: allocate dentry failed\n");
 435                 return -ENOMEM;
 436         }
 437
 438         return proc_setup_self(s);
 439 }