linux/fs/proc/proc_sysctl.c
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   1/*
   2 * /proc/sys support
   3 */
   4#include <linux/init.h>
   5#include <linux/sysctl.h>
   6#include <linux/proc_fs.h>
   7#include <linux/security.h>
   8#include <linux/namei.h>
   9#include "internal.h"
  10
  11static const struct dentry_operations proc_sys_dentry_operations;
  12static const struct file_operations proc_sys_file_operations;
  13static const struct inode_operations proc_sys_inode_operations;
  14static const struct file_operations proc_sys_dir_file_operations;
  15static const struct inode_operations proc_sys_dir_operations;
  16
  17static struct inode *proc_sys_make_inode(struct super_block *sb,
  18                struct ctl_table_header *head, struct ctl_table *table)
  19{
  20        struct inode *inode;
  21        struct proc_inode *ei;
  22
  23        inode = new_inode(sb);
  24        if (!inode)
  25                goto out;
  26
  27        inode->i_ino = get_next_ino();
  28
  29        sysctl_head_get(head);
  30        ei = PROC_I(inode);
  31        ei->sysctl = head;
  32        ei->sysctl_entry = table;
  33
  34        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  35        inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
  36        inode->i_mode = table->mode;
  37        if (!table->child) {
  38                inode->i_mode |= S_IFREG;
  39                inode->i_op = &proc_sys_inode_operations;
  40                inode->i_fop = &proc_sys_file_operations;
  41        } else {
  42                inode->i_mode |= S_IFDIR;
  43                inode->i_nlink = 0;
  44                inode->i_op = &proc_sys_dir_operations;
  45                inode->i_fop = &proc_sys_dir_file_operations;
  46        }
  47out:
  48        return inode;
  49}
  50
  51static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
  52{
  53        int len;
  54        for ( ; p->procname; p++) {
  55
  56                if (!p->procname)
  57                        continue;
  58
  59                len = strlen(p->procname);
  60                if (len != name->len)
  61                        continue;
  62
  63                if (memcmp(p->procname, name->name, len) != 0)
  64                        continue;
  65
  66                /* I have a match */
  67                return p;
  68        }
  69        return NULL;
  70}
  71
  72static struct ctl_table_header *grab_header(struct inode *inode)
  73{
  74        if (PROC_I(inode)->sysctl)
  75                return sysctl_head_grab(PROC_I(inode)->sysctl);
  76        else
  77                return sysctl_head_next(NULL);
  78}
  79
  80static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
  81                                        struct nameidata *nd)
  82{
  83        struct ctl_table_header *head = grab_header(dir);
  84        struct ctl_table *table = PROC_I(dir)->sysctl_entry;
  85        struct ctl_table_header *h = NULL;
  86        struct qstr *name = &dentry->d_name;
  87        struct ctl_table *p;
  88        struct inode *inode;
  89        struct dentry *err = ERR_PTR(-ENOENT);
  90
  91        if (IS_ERR(head))
  92                return ERR_CAST(head);
  93
  94        if (table && !table->child) {
  95                WARN_ON(1);
  96                goto out;
  97        }
  98
  99        table = table ? table->child : head->ctl_table;
 100
 101        p = find_in_table(table, name);
 102        if (!p) {
 103                for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 104                        if (h->attached_to != table)
 105                                continue;
 106                        p = find_in_table(h->attached_by, name);
 107                        if (p)
 108                                break;
 109                }
 110        }
 111
 112        if (!p)
 113                goto out;
 114
 115        err = ERR_PTR(-ENOMEM);
 116        inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
 117        if (h)
 118                sysctl_head_finish(h);
 119
 120        if (!inode)
 121                goto out;
 122
 123        err = NULL;
 124        d_set_d_op(dentry, &proc_sys_dentry_operations);
 125        d_add(dentry, inode);
 126
 127out:
 128        sysctl_head_finish(head);
 129        return err;
 130}
 131
 132static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
 133                size_t count, loff_t *ppos, int write)
 134{
 135        struct inode *inode = filp->f_path.dentry->d_inode;
 136        struct ctl_table_header *head = grab_header(inode);
 137        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 138        ssize_t error;
 139        size_t res;
 140
 141        if (IS_ERR(head))
 142                return PTR_ERR(head);
 143
 144        /*
 145         * At this point we know that the sysctl was not unregistered
 146         * and won't be until we finish.
 147         */
 148        error = -EPERM;
 149        if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
 150                goto out;
 151
 152        /* if that can happen at all, it should be -EINVAL, not -EISDIR */
 153        error = -EINVAL;
 154        if (!table->proc_handler)
 155                goto out;
 156
 157        /* careful: calling conventions are nasty here */
 158        res = count;
 159        error = table->proc_handler(table, write, buf, &res, ppos);
 160        if (!error)
 161                error = res;
 162out:
 163        sysctl_head_finish(head);
 164
 165        return error;
 166}
 167
 168static ssize_t proc_sys_read(struct file *filp, char __user *buf,
 169                                size_t count, loff_t *ppos)
 170{
 171        return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
 172}
 173
 174static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
 175                                size_t count, loff_t *ppos)
 176{
 177        return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
 178}
 179
 180
 181static int proc_sys_fill_cache(struct file *filp, void *dirent,
 182                                filldir_t filldir,
 183                                struct ctl_table_header *head,
 184                                struct ctl_table *table)
 185{
 186        struct dentry *child, *dir = filp->f_path.dentry;
 187        struct inode *inode;
 188        struct qstr qname;
 189        ino_t ino = 0;
 190        unsigned type = DT_UNKNOWN;
 191
 192        qname.name = table->procname;
 193        qname.len  = strlen(table->procname);
 194        qname.hash = full_name_hash(qname.name, qname.len);
 195
 196        child = d_lookup(dir, &qname);
 197        if (!child) {
 198                child = d_alloc(dir, &qname);
 199                if (child) {
 200                        inode = proc_sys_make_inode(dir->d_sb, head, table);
 201                        if (!inode) {
 202                                dput(child);
 203                                return -ENOMEM;
 204                        } else {
 205                                d_set_d_op(child, &proc_sys_dentry_operations);
 206                                d_add(child, inode);
 207                        }
 208                } else {
 209                        return -ENOMEM;
 210                }
 211        }
 212        inode = child->d_inode;
 213        ino  = inode->i_ino;
 214        type = inode->i_mode >> 12;
 215        dput(child);
 216        return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
 217}
 218
 219static int scan(struct ctl_table_header *head, ctl_table *table,
 220                unsigned long *pos, struct file *file,
 221                void *dirent, filldir_t filldir)
 222{
 223
 224        for (; table->procname; table++, (*pos)++) {
 225                int res;
 226
 227                /* Can't do anything without a proc name */
 228                if (!table->procname)
 229                        continue;
 230
 231                if (*pos < file->f_pos)
 232                        continue;
 233
 234                res = proc_sys_fill_cache(file, dirent, filldir, head, table);
 235                if (res)
 236                        return res;
 237
 238                file->f_pos = *pos + 1;
 239        }
 240        return 0;
 241}
 242
 243static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
 244{
 245        struct dentry *dentry = filp->f_path.dentry;
 246        struct inode *inode = dentry->d_inode;
 247        struct ctl_table_header *head = grab_header(inode);
 248        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 249        struct ctl_table_header *h = NULL;
 250        unsigned long pos;
 251        int ret = -EINVAL;
 252
 253        if (IS_ERR(head))
 254                return PTR_ERR(head);
 255
 256        if (table && !table->child) {
 257                WARN_ON(1);
 258                goto out;
 259        }
 260
 261        table = table ? table->child : head->ctl_table;
 262
 263        ret = 0;
 264        /* Avoid a switch here: arm builds fail with missing __cmpdi2 */
 265        if (filp->f_pos == 0) {
 266                if (filldir(dirent, ".", 1, filp->f_pos,
 267                                inode->i_ino, DT_DIR) < 0)
 268                        goto out;
 269                filp->f_pos++;
 270        }
 271        if (filp->f_pos == 1) {
 272                if (filldir(dirent, "..", 2, filp->f_pos,
 273                                parent_ino(dentry), DT_DIR) < 0)
 274                        goto out;
 275                filp->f_pos++;
 276        }
 277        pos = 2;
 278
 279        ret = scan(head, table, &pos, filp, dirent, filldir);
 280        if (ret)
 281                goto out;
 282
 283        for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
 284                if (h->attached_to != table)
 285                        continue;
 286                ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
 287                if (ret) {
 288                        sysctl_head_finish(h);
 289                        break;
 290                }
 291        }
 292        ret = 1;
 293out:
 294        sysctl_head_finish(head);
 295        return ret;
 296}
 297
 298static int proc_sys_permission(struct inode *inode, int mask,unsigned int flags)
 299{
 300        /*
 301         * sysctl entries that are not writeable,
 302         * are _NOT_ writeable, capabilities or not.
 303         */
 304        struct ctl_table_header *head;
 305        struct ctl_table *table;
 306        int error;
 307
 308        if (flags & IPERM_FLAG_RCU)
 309                return -ECHILD;
 310
 311        /* Executable files are not allowed under /proc/sys/ */
 312        if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 313                return -EACCES;
 314
 315        head = grab_header(inode);
 316        if (IS_ERR(head))
 317                return PTR_ERR(head);
 318
 319        table = PROC_I(inode)->sysctl_entry;
 320        if (!table) /* global root - r-xr-xr-x */
 321                error = mask & MAY_WRITE ? -EACCES : 0;
 322        else /* Use the permissions on the sysctl table entry */
 323                error = sysctl_perm(head->root, table, mask);
 324
 325        sysctl_head_finish(head);
 326        return error;
 327}
 328
 329static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
 330{
 331        struct inode *inode = dentry->d_inode;
 332        int error;
 333
 334        if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 335                return -EPERM;
 336
 337        error = inode_change_ok(inode, attr);
 338        if (error)
 339                return error;
 340
 341        if ((attr->ia_valid & ATTR_SIZE) &&
 342            attr->ia_size != i_size_read(inode)) {
 343                error = vmtruncate(inode, attr->ia_size);
 344                if (error)
 345                        return error;
 346        }
 347
 348        setattr_copy(inode, attr);
 349        mark_inode_dirty(inode);
 350        return 0;
 351}
 352
 353static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 354{
 355        struct inode *inode = dentry->d_inode;
 356        struct ctl_table_header *head = grab_header(inode);
 357        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 358
 359        if (IS_ERR(head))
 360                return PTR_ERR(head);
 361
 362        generic_fillattr(inode, stat);
 363        if (table)
 364                stat->mode = (stat->mode & S_IFMT) | table->mode;
 365
 366        sysctl_head_finish(head);
 367        return 0;
 368}
 369
 370static const struct file_operations proc_sys_file_operations = {
 371        .read           = proc_sys_read,
 372        .write          = proc_sys_write,
 373        .llseek         = default_llseek,
 374};
 375
 376static const struct file_operations proc_sys_dir_file_operations = {
 377        .readdir        = proc_sys_readdir,
 378        .llseek         = generic_file_llseek,
 379};
 380
 381static const struct inode_operations proc_sys_inode_operations = {
 382        .permission     = proc_sys_permission,
 383        .setattr        = proc_sys_setattr,
 384        .getattr        = proc_sys_getattr,
 385};
 386
 387static const struct inode_operations proc_sys_dir_operations = {
 388        .lookup         = proc_sys_lookup,
 389        .permission     = proc_sys_permission,
 390        .setattr        = proc_sys_setattr,
 391        .getattr        = proc_sys_getattr,
 392};
 393
 394static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
 395{
 396        if (nd->flags & LOOKUP_RCU)
 397                return -ECHILD;
 398        return !PROC_I(dentry->d_inode)->sysctl->unregistering;
 399}
 400
 401static int proc_sys_delete(const struct dentry *dentry)
 402{
 403        return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
 404}
 405
 406static int proc_sys_compare(const struct dentry *parent,
 407                const struct inode *pinode,
 408                const struct dentry *dentry, const struct inode *inode,
 409                unsigned int len, const char *str, const struct qstr *name)
 410{
 411        struct ctl_table_header *head;
 412        /* Although proc doesn't have negative dentries, rcu-walk means
 413         * that inode here can be NULL */
 414        /* AV: can it, indeed? */
 415        if (!inode)
 416                return 1;
 417        if (name->len != len)
 418                return 1;
 419        if (memcmp(name->name, str, len))
 420                return 1;
 421        head = rcu_dereference(PROC_I(inode)->sysctl);
 422        return !head || !sysctl_is_seen(head);
 423}
 424
 425static const struct dentry_operations proc_sys_dentry_operations = {
 426        .d_revalidate   = proc_sys_revalidate,
 427        .d_delete       = proc_sys_delete,
 428        .d_compare      = proc_sys_compare,
 429};
 430
 431int __init proc_sys_init(void)
 432{
 433        struct proc_dir_entry *proc_sys_root;
 434
 435        proc_sys_root = proc_mkdir("sys", NULL);
 436        proc_sys_root->proc_iops = &proc_sys_dir_operations;
 437        proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
 438        proc_sys_root->nlink = 0;
 439        return 0;
 440}
 441