linux/fs/proc/proc_sysctl.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * /proc/sys support
   4 */
   5#include <linux/init.h>
   6#include <linux/sysctl.h>
   7#include <linux/poll.h>
   8#include <linux/proc_fs.h>
   9#include <linux/printk.h>
  10#include <linux/security.h>
  11#include <linux/sched.h>
  12#include <linux/cred.h>
  13#include <linux/namei.h>
  14#include <linux/mm.h>
  15#include <linux/uio.h>
  16#include <linux/module.h>
  17#include <linux/bpf-cgroup.h>
  18#include <linux/mount.h>
  19#include "internal.h"
  20
  21static const struct dentry_operations proc_sys_dentry_operations;
  22static const struct file_operations proc_sys_file_operations;
  23static const struct inode_operations proc_sys_inode_operations;
  24static const struct file_operations proc_sys_dir_file_operations;
  25static const struct inode_operations proc_sys_dir_operations;
  26
  27/* shared constants to be used in various sysctls */
  28const int sysctl_vals[] = { 0, 1, INT_MAX };
  29EXPORT_SYMBOL(sysctl_vals);
  30
  31/* Support for permanently empty directories */
  32
  33struct ctl_table sysctl_mount_point[] = {
  34        { }
  35};
  36
  37static bool is_empty_dir(struct ctl_table_header *head)
  38{
  39        return head->ctl_table[0].child == sysctl_mount_point;
  40}
  41
  42static void set_empty_dir(struct ctl_dir *dir)
  43{
  44        dir->header.ctl_table[0].child = sysctl_mount_point;
  45}
  46
  47static void clear_empty_dir(struct ctl_dir *dir)
  48
  49{
  50        dir->header.ctl_table[0].child = NULL;
  51}
  52
  53void proc_sys_poll_notify(struct ctl_table_poll *poll)
  54{
  55        if (!poll)
  56                return;
  57
  58        atomic_inc(&poll->event);
  59        wake_up_interruptible(&poll->wait);
  60}
  61
  62static struct ctl_table root_table[] = {
  63        {
  64                .procname = "",
  65                .mode = S_IFDIR|S_IRUGO|S_IXUGO,
  66        },
  67        { }
  68};
  69static struct ctl_table_root sysctl_table_root = {
  70        .default_set.dir.header = {
  71                {{.count = 1,
  72                  .nreg = 1,
  73                  .ctl_table = root_table }},
  74                .ctl_table_arg = root_table,
  75                .root = &sysctl_table_root,
  76                .set = &sysctl_table_root.default_set,
  77        },
  78};
  79
  80static DEFINE_SPINLOCK(sysctl_lock);
  81
  82static void drop_sysctl_table(struct ctl_table_header *header);
  83static int sysctl_follow_link(struct ctl_table_header **phead,
  84        struct ctl_table **pentry);
  85static int insert_links(struct ctl_table_header *head);
  86static void put_links(struct ctl_table_header *header);
  87
  88static void sysctl_print_dir(struct ctl_dir *dir)
  89{
  90        if (dir->header.parent)
  91                sysctl_print_dir(dir->header.parent);
  92        pr_cont("%s/", dir->header.ctl_table[0].procname);
  93}
  94
  95static int namecmp(const char *name1, int len1, const char *name2, int len2)
  96{
  97        int cmp;
  98
  99        cmp = memcmp(name1, name2, min(len1, len2));
 100        if (cmp == 0)
 101                cmp = len1 - len2;
 102        return cmp;
 103}
 104
 105/* Called under sysctl_lock */
 106static struct ctl_table *find_entry(struct ctl_table_header **phead,
 107        struct ctl_dir *dir, const char *name, int namelen)
 108{
 109        struct ctl_table_header *head;
 110        struct ctl_table *entry;
 111        struct rb_node *node = dir->root.rb_node;
 112
 113        while (node)
 114        {
 115                struct ctl_node *ctl_node;
 116                const char *procname;
 117                int cmp;
 118
 119                ctl_node = rb_entry(node, struct ctl_node, node);
 120                head = ctl_node->header;
 121                entry = &head->ctl_table[ctl_node - head->node];
 122                procname = entry->procname;
 123
 124                cmp = namecmp(name, namelen, procname, strlen(procname));
 125                if (cmp < 0)
 126                        node = node->rb_left;
 127                else if (cmp > 0)
 128                        node = node->rb_right;
 129                else {
 130                        *phead = head;
 131                        return entry;
 132                }
 133        }
 134        return NULL;
 135}
 136
 137static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
 138{
 139        struct rb_node *node = &head->node[entry - head->ctl_table].node;
 140        struct rb_node **p = &head->parent->root.rb_node;
 141        struct rb_node *parent = NULL;
 142        const char *name = entry->procname;
 143        int namelen = strlen(name);
 144
 145        while (*p) {
 146                struct ctl_table_header *parent_head;
 147                struct ctl_table *parent_entry;
 148                struct ctl_node *parent_node;
 149                const char *parent_name;
 150                int cmp;
 151
 152                parent = *p;
 153                parent_node = rb_entry(parent, struct ctl_node, node);
 154                parent_head = parent_node->header;
 155                parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
 156                parent_name = parent_entry->procname;
 157
 158                cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
 159                if (cmp < 0)
 160                        p = &(*p)->rb_left;
 161                else if (cmp > 0)
 162                        p = &(*p)->rb_right;
 163                else {
 164                        pr_err("sysctl duplicate entry: ");
 165                        sysctl_print_dir(head->parent);
 166                        pr_cont("/%s\n", entry->procname);
 167                        return -EEXIST;
 168                }
 169        }
 170
 171        rb_link_node(node, parent, p);
 172        rb_insert_color(node, &head->parent->root);
 173        return 0;
 174}
 175
 176static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
 177{
 178        struct rb_node *node = &head->node[entry - head->ctl_table].node;
 179
 180        rb_erase(node, &head->parent->root);
 181}
 182
 183static void init_header(struct ctl_table_header *head,
 184        struct ctl_table_root *root, struct ctl_table_set *set,
 185        struct ctl_node *node, struct ctl_table *table)
 186{
 187        head->ctl_table = table;
 188        head->ctl_table_arg = table;
 189        head->used = 0;
 190        head->count = 1;
 191        head->nreg = 1;
 192        head->unregistering = NULL;
 193        head->root = root;
 194        head->set = set;
 195        head->parent = NULL;
 196        head->node = node;
 197        INIT_HLIST_HEAD(&head->inodes);
 198        if (node) {
 199                struct ctl_table *entry;
 200                for (entry = table; entry->procname; entry++, node++)
 201                        node->header = head;
 202        }
 203}
 204
 205static void erase_header(struct ctl_table_header *head)
 206{
 207        struct ctl_table *entry;
 208        for (entry = head->ctl_table; entry->procname; entry++)
 209                erase_entry(head, entry);
 210}
 211
 212static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
 213{
 214        struct ctl_table *entry;
 215        int err;
 216
 217        /* Is this a permanently empty directory? */
 218        if (is_empty_dir(&dir->header))
 219                return -EROFS;
 220
 221        /* Am I creating a permanently empty directory? */
 222        if (header->ctl_table == sysctl_mount_point) {
 223                if (!RB_EMPTY_ROOT(&dir->root))
 224                        return -EINVAL;
 225                set_empty_dir(dir);
 226        }
 227
 228        dir->header.nreg++;
 229        header->parent = dir;
 230        err = insert_links(header);
 231        if (err)
 232                goto fail_links;
 233        for (entry = header->ctl_table; entry->procname; entry++) {
 234                err = insert_entry(header, entry);
 235                if (err)
 236                        goto fail;
 237        }
 238        return 0;
 239fail:
 240        erase_header(header);
 241        put_links(header);
 242fail_links:
 243        if (header->ctl_table == sysctl_mount_point)
 244                clear_empty_dir(dir);
 245        header->parent = NULL;
 246        drop_sysctl_table(&dir->header);
 247        return err;
 248}
 249
 250/* called under sysctl_lock */
 251static int use_table(struct ctl_table_header *p)
 252{
 253        if (unlikely(p->unregistering))
 254                return 0;
 255        p->used++;
 256        return 1;
 257}
 258
 259/* called under sysctl_lock */
 260static void unuse_table(struct ctl_table_header *p)
 261{
 262        if (!--p->used)
 263                if (unlikely(p->unregistering))
 264                        complete(p->unregistering);
 265}
 266
 267static void proc_sys_invalidate_dcache(struct ctl_table_header *head)
 268{
 269        proc_invalidate_siblings_dcache(&head->inodes, &sysctl_lock);
 270}
 271
 272/* called under sysctl_lock, will reacquire if has to wait */
 273static void start_unregistering(struct ctl_table_header *p)
 274{
 275        /*
 276         * if p->used is 0, nobody will ever touch that entry again;
 277         * we'll eliminate all paths to it before dropping sysctl_lock
 278         */
 279        if (unlikely(p->used)) {
 280                struct completion wait;
 281                init_completion(&wait);
 282                p->unregistering = &wait;
 283                spin_unlock(&sysctl_lock);
 284                wait_for_completion(&wait);
 285        } else {
 286                /* anything non-NULL; we'll never dereference it */
 287                p->unregistering = ERR_PTR(-EINVAL);
 288                spin_unlock(&sysctl_lock);
 289        }
 290        /*
 291         * Invalidate dentries for unregistered sysctls: namespaced sysctls
 292         * can have duplicate names and contaminate dcache very badly.
 293         */
 294        proc_sys_invalidate_dcache(p);
 295        /*
 296         * do not remove from the list until nobody holds it; walking the
 297         * list in do_sysctl() relies on that.
 298         */
 299        spin_lock(&sysctl_lock);
 300        erase_header(p);
 301}
 302
 303static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
 304{
 305        BUG_ON(!head);
 306        spin_lock(&sysctl_lock);
 307        if (!use_table(head))
 308                head = ERR_PTR(-ENOENT);
 309        spin_unlock(&sysctl_lock);
 310        return head;
 311}
 312
 313static void sysctl_head_finish(struct ctl_table_header *head)
 314{
 315        if (!head)
 316                return;
 317        spin_lock(&sysctl_lock);
 318        unuse_table(head);
 319        spin_unlock(&sysctl_lock);
 320}
 321
 322static struct ctl_table_set *
 323lookup_header_set(struct ctl_table_root *root)
 324{
 325        struct ctl_table_set *set = &root->default_set;
 326        if (root->lookup)
 327                set = root->lookup(root);
 328        return set;
 329}
 330
 331static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
 332                                      struct ctl_dir *dir,
 333                                      const char *name, int namelen)
 334{
 335        struct ctl_table_header *head;
 336        struct ctl_table *entry;
 337
 338        spin_lock(&sysctl_lock);
 339        entry = find_entry(&head, dir, name, namelen);
 340        if (entry && use_table(head))
 341                *phead = head;
 342        else
 343                entry = NULL;
 344        spin_unlock(&sysctl_lock);
 345        return entry;
 346}
 347
 348static struct ctl_node *first_usable_entry(struct rb_node *node)
 349{
 350        struct ctl_node *ctl_node;
 351
 352        for (;node; node = rb_next(node)) {
 353                ctl_node = rb_entry(node, struct ctl_node, node);
 354                if (use_table(ctl_node->header))
 355                        return ctl_node;
 356        }
 357        return NULL;
 358}
 359
 360static void first_entry(struct ctl_dir *dir,
 361        struct ctl_table_header **phead, struct ctl_table **pentry)
 362{
 363        struct ctl_table_header *head = NULL;
 364        struct ctl_table *entry = NULL;
 365        struct ctl_node *ctl_node;
 366
 367        spin_lock(&sysctl_lock);
 368        ctl_node = first_usable_entry(rb_first(&dir->root));
 369        spin_unlock(&sysctl_lock);
 370        if (ctl_node) {
 371                head = ctl_node->header;
 372                entry = &head->ctl_table[ctl_node - head->node];
 373        }
 374        *phead = head;
 375        *pentry = entry;
 376}
 377
 378static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
 379{
 380        struct ctl_table_header *head = *phead;
 381        struct ctl_table *entry = *pentry;
 382        struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
 383
 384        spin_lock(&sysctl_lock);
 385        unuse_table(head);
 386
 387        ctl_node = first_usable_entry(rb_next(&ctl_node->node));
 388        spin_unlock(&sysctl_lock);
 389        head = NULL;
 390        if (ctl_node) {
 391                head = ctl_node->header;
 392                entry = &head->ctl_table[ctl_node - head->node];
 393        }
 394        *phead = head;
 395        *pentry = entry;
 396}
 397
 398/*
 399 * sysctl_perm does NOT grant the superuser all rights automatically, because
 400 * some sysctl variables are readonly even to root.
 401 */
 402
 403static int test_perm(int mode, int op)
 404{
 405        if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
 406                mode >>= 6;
 407        else if (in_egroup_p(GLOBAL_ROOT_GID))
 408                mode >>= 3;
 409        if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
 410                return 0;
 411        return -EACCES;
 412}
 413
 414static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
 415{
 416        struct ctl_table_root *root = head->root;
 417        int mode;
 418
 419        if (root->permissions)
 420                mode = root->permissions(head, table);
 421        else
 422                mode = table->mode;
 423
 424        return test_perm(mode, op);
 425}
 426
 427static struct inode *proc_sys_make_inode(struct super_block *sb,
 428                struct ctl_table_header *head, struct ctl_table *table)
 429{
 430        struct ctl_table_root *root = head->root;
 431        struct inode *inode;
 432        struct proc_inode *ei;
 433
 434        inode = new_inode(sb);
 435        if (!inode)
 436                return ERR_PTR(-ENOMEM);
 437
 438        inode->i_ino = get_next_ino();
 439
 440        ei = PROC_I(inode);
 441
 442        spin_lock(&sysctl_lock);
 443        if (unlikely(head->unregistering)) {
 444                spin_unlock(&sysctl_lock);
 445                iput(inode);
 446                return ERR_PTR(-ENOENT);
 447        }
 448        ei->sysctl = head;
 449        ei->sysctl_entry = table;
 450        hlist_add_head_rcu(&ei->sibling_inodes, &head->inodes);
 451        head->count++;
 452        spin_unlock(&sysctl_lock);
 453
 454        inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 455        inode->i_mode = table->mode;
 456        if (!S_ISDIR(table->mode)) {
 457                inode->i_mode |= S_IFREG;
 458                inode->i_op = &proc_sys_inode_operations;
 459                inode->i_fop = &proc_sys_file_operations;
 460        } else {
 461                inode->i_mode |= S_IFDIR;
 462                inode->i_op = &proc_sys_dir_operations;
 463                inode->i_fop = &proc_sys_dir_file_operations;
 464                if (is_empty_dir(head))
 465                        make_empty_dir_inode(inode);
 466        }
 467
 468        if (root->set_ownership)
 469                root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
 470        else {
 471                inode->i_uid = GLOBAL_ROOT_UID;
 472                inode->i_gid = GLOBAL_ROOT_GID;
 473        }
 474
 475        return inode;
 476}
 477
 478void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
 479{
 480        spin_lock(&sysctl_lock);
 481        hlist_del_init_rcu(&PROC_I(inode)->sibling_inodes);
 482        if (!--head->count)
 483                kfree_rcu(head, rcu);
 484        spin_unlock(&sysctl_lock);
 485}
 486
 487static struct ctl_table_header *grab_header(struct inode *inode)
 488{
 489        struct ctl_table_header *head = PROC_I(inode)->sysctl;
 490        if (!head)
 491                head = &sysctl_table_root.default_set.dir.header;
 492        return sysctl_head_grab(head);
 493}
 494
 495static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
 496                                        unsigned int flags)
 497{
 498        struct ctl_table_header *head = grab_header(dir);
 499        struct ctl_table_header *h = NULL;
 500        const struct qstr *name = &dentry->d_name;
 501        struct ctl_table *p;
 502        struct inode *inode;
 503        struct dentry *err = ERR_PTR(-ENOENT);
 504        struct ctl_dir *ctl_dir;
 505        int ret;
 506
 507        if (IS_ERR(head))
 508                return ERR_CAST(head);
 509
 510        ctl_dir = container_of(head, struct ctl_dir, header);
 511
 512        p = lookup_entry(&h, ctl_dir, name->name, name->len);
 513        if (!p)
 514                goto out;
 515
 516        if (S_ISLNK(p->mode)) {
 517                ret = sysctl_follow_link(&h, &p);
 518                err = ERR_PTR(ret);
 519                if (ret)
 520                        goto out;
 521        }
 522
 523        inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
 524        if (IS_ERR(inode)) {
 525                err = ERR_CAST(inode);
 526                goto out;
 527        }
 528
 529        d_set_d_op(dentry, &proc_sys_dentry_operations);
 530        err = d_splice_alias(inode, dentry);
 531
 532out:
 533        if (h)
 534                sysctl_head_finish(h);
 535        sysctl_head_finish(head);
 536        return err;
 537}
 538
 539static ssize_t proc_sys_call_handler(struct kiocb *iocb, struct iov_iter *iter,
 540                int write)
 541{
 542        struct inode *inode = file_inode(iocb->ki_filp);
 543        struct ctl_table_header *head = grab_header(inode);
 544        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 545        size_t count = iov_iter_count(iter);
 546        char *kbuf;
 547        ssize_t error;
 548
 549        if (IS_ERR(head))
 550                return PTR_ERR(head);
 551
 552        /*
 553         * At this point we know that the sysctl was not unregistered
 554         * and won't be until we finish.
 555         */
 556        error = -EPERM;
 557        if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
 558                goto out;
 559
 560        /* if that can happen at all, it should be -EINVAL, not -EISDIR */
 561        error = -EINVAL;
 562        if (!table->proc_handler)
 563                goto out;
 564
 565        /* don't even try if the size is too large */
 566        error = -ENOMEM;
 567        if (count >= KMALLOC_MAX_SIZE)
 568                goto out;
 569        kbuf = kvzalloc(count + 1, GFP_KERNEL);
 570        if (!kbuf)
 571                goto out;
 572
 573        if (write) {
 574                error = -EFAULT;
 575                if (!copy_from_iter_full(kbuf, count, iter))
 576                        goto out_free_buf;
 577                kbuf[count] = '\0';
 578        }
 579
 580        error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, &kbuf, &count,
 581                                           &iocb->ki_pos);
 582        if (error)
 583                goto out_free_buf;
 584
 585        /* careful: calling conventions are nasty here */
 586        error = table->proc_handler(table, write, kbuf, &count, &iocb->ki_pos);
 587        if (error)
 588                goto out_free_buf;
 589
 590        if (!write) {
 591                error = -EFAULT;
 592                if (copy_to_iter(kbuf, count, iter) < count)
 593                        goto out_free_buf;
 594        }
 595
 596        error = count;
 597out_free_buf:
 598        kvfree(kbuf);
 599out:
 600        sysctl_head_finish(head);
 601
 602        return error;
 603}
 604
 605static ssize_t proc_sys_read(struct kiocb *iocb, struct iov_iter *iter)
 606{
 607        return proc_sys_call_handler(iocb, iter, 0);
 608}
 609
 610static ssize_t proc_sys_write(struct kiocb *iocb, struct iov_iter *iter)
 611{
 612        return proc_sys_call_handler(iocb, iter, 1);
 613}
 614
 615static int proc_sys_open(struct inode *inode, struct file *filp)
 616{
 617        struct ctl_table_header *head = grab_header(inode);
 618        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 619
 620        /* sysctl was unregistered */
 621        if (IS_ERR(head))
 622                return PTR_ERR(head);
 623
 624        if (table->poll)
 625                filp->private_data = proc_sys_poll_event(table->poll);
 626
 627        sysctl_head_finish(head);
 628
 629        return 0;
 630}
 631
 632static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
 633{
 634        struct inode *inode = file_inode(filp);
 635        struct ctl_table_header *head = grab_header(inode);
 636        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 637        __poll_t ret = DEFAULT_POLLMASK;
 638        unsigned long event;
 639
 640        /* sysctl was unregistered */
 641        if (IS_ERR(head))
 642                return EPOLLERR | EPOLLHUP;
 643
 644        if (!table->proc_handler)
 645                goto out;
 646
 647        if (!table->poll)
 648                goto out;
 649
 650        event = (unsigned long)filp->private_data;
 651        poll_wait(filp, &table->poll->wait, wait);
 652
 653        if (event != atomic_read(&table->poll->event)) {
 654                filp->private_data = proc_sys_poll_event(table->poll);
 655                ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
 656        }
 657
 658out:
 659        sysctl_head_finish(head);
 660
 661        return ret;
 662}
 663
 664static bool proc_sys_fill_cache(struct file *file,
 665                                struct dir_context *ctx,
 666                                struct ctl_table_header *head,
 667                                struct ctl_table *table)
 668{
 669        struct dentry *child, *dir = file->f_path.dentry;
 670        struct inode *inode;
 671        struct qstr qname;
 672        ino_t ino = 0;
 673        unsigned type = DT_UNKNOWN;
 674
 675        qname.name = table->procname;
 676        qname.len  = strlen(table->procname);
 677        qname.hash = full_name_hash(dir, qname.name, qname.len);
 678
 679        child = d_lookup(dir, &qname);
 680        if (!child) {
 681                DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
 682                child = d_alloc_parallel(dir, &qname, &wq);
 683                if (IS_ERR(child))
 684                        return false;
 685                if (d_in_lookup(child)) {
 686                        struct dentry *res;
 687                        inode = proc_sys_make_inode(dir->d_sb, head, table);
 688                        if (IS_ERR(inode)) {
 689                                d_lookup_done(child);
 690                                dput(child);
 691                                return false;
 692                        }
 693                        d_set_d_op(child, &proc_sys_dentry_operations);
 694                        res = d_splice_alias(inode, child);
 695                        d_lookup_done(child);
 696                        if (unlikely(res)) {
 697                                if (IS_ERR(res)) {
 698                                        dput(child);
 699                                        return false;
 700                                }
 701                                dput(child);
 702                                child = res;
 703                        }
 704                }
 705        }
 706        inode = d_inode(child);
 707        ino  = inode->i_ino;
 708        type = inode->i_mode >> 12;
 709        dput(child);
 710        return dir_emit(ctx, qname.name, qname.len, ino, type);
 711}
 712
 713static bool proc_sys_link_fill_cache(struct file *file,
 714                                    struct dir_context *ctx,
 715                                    struct ctl_table_header *head,
 716                                    struct ctl_table *table)
 717{
 718        bool ret = true;
 719
 720        head = sysctl_head_grab(head);
 721        if (IS_ERR(head))
 722                return false;
 723
 724        /* It is not an error if we can not follow the link ignore it */
 725        if (sysctl_follow_link(&head, &table))
 726                goto out;
 727
 728        ret = proc_sys_fill_cache(file, ctx, head, table);
 729out:
 730        sysctl_head_finish(head);
 731        return ret;
 732}
 733
 734static int scan(struct ctl_table_header *head, struct ctl_table *table,
 735                unsigned long *pos, struct file *file,
 736                struct dir_context *ctx)
 737{
 738        bool res;
 739
 740        if ((*pos)++ < ctx->pos)
 741                return true;
 742
 743        if (unlikely(S_ISLNK(table->mode)))
 744                res = proc_sys_link_fill_cache(file, ctx, head, table);
 745        else
 746                res = proc_sys_fill_cache(file, ctx, head, table);
 747
 748        if (res)
 749                ctx->pos = *pos;
 750
 751        return res;
 752}
 753
 754static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
 755{
 756        struct ctl_table_header *head = grab_header(file_inode(file));
 757        struct ctl_table_header *h = NULL;
 758        struct ctl_table *entry;
 759        struct ctl_dir *ctl_dir;
 760        unsigned long pos;
 761
 762        if (IS_ERR(head))
 763                return PTR_ERR(head);
 764
 765        ctl_dir = container_of(head, struct ctl_dir, header);
 766
 767        if (!dir_emit_dots(file, ctx))
 768                goto out;
 769
 770        pos = 2;
 771
 772        for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
 773                if (!scan(h, entry, &pos, file, ctx)) {
 774                        sysctl_head_finish(h);
 775                        break;
 776                }
 777        }
 778out:
 779        sysctl_head_finish(head);
 780        return 0;
 781}
 782
 783static int proc_sys_permission(struct user_namespace *mnt_userns,
 784                               struct inode *inode, int mask)
 785{
 786        /*
 787         * sysctl entries that are not writeable,
 788         * are _NOT_ writeable, capabilities or not.
 789         */
 790        struct ctl_table_header *head;
 791        struct ctl_table *table;
 792        int error;
 793
 794        /* Executable files are not allowed under /proc/sys/ */
 795        if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
 796                return -EACCES;
 797
 798        head = grab_header(inode);
 799        if (IS_ERR(head))
 800                return PTR_ERR(head);
 801
 802        table = PROC_I(inode)->sysctl_entry;
 803        if (!table) /* global root - r-xr-xr-x */
 804                error = mask & MAY_WRITE ? -EACCES : 0;
 805        else /* Use the permissions on the sysctl table entry */
 806                error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
 807
 808        sysctl_head_finish(head);
 809        return error;
 810}
 811
 812static int proc_sys_setattr(struct user_namespace *mnt_userns,
 813                            struct dentry *dentry, struct iattr *attr)
 814{
 815        struct inode *inode = d_inode(dentry);
 816        int error;
 817
 818        if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
 819                return -EPERM;
 820
 821        error = setattr_prepare(&init_user_ns, dentry, attr);
 822        if (error)
 823                return error;
 824
 825        setattr_copy(&init_user_ns, inode, attr);
 826        mark_inode_dirty(inode);
 827        return 0;
 828}
 829
 830static int proc_sys_getattr(struct user_namespace *mnt_userns,
 831                            const struct path *path, struct kstat *stat,
 832                            u32 request_mask, unsigned int query_flags)
 833{
 834        struct inode *inode = d_inode(path->dentry);
 835        struct ctl_table_header *head = grab_header(inode);
 836        struct ctl_table *table = PROC_I(inode)->sysctl_entry;
 837
 838        if (IS_ERR(head))
 839                return PTR_ERR(head);
 840
 841        generic_fillattr(&init_user_ns, inode, stat);
 842        if (table)
 843                stat->mode = (stat->mode & S_IFMT) | table->mode;
 844
 845        sysctl_head_finish(head);
 846        return 0;
 847}
 848
 849static const struct file_operations proc_sys_file_operations = {
 850        .open           = proc_sys_open,
 851        .poll           = proc_sys_poll,
 852        .read_iter      = proc_sys_read,
 853        .write_iter     = proc_sys_write,
 854        .splice_read    = generic_file_splice_read,
 855        .splice_write   = iter_file_splice_write,
 856        .llseek         = default_llseek,
 857};
 858
 859static const struct file_operations proc_sys_dir_file_operations = {
 860        .read           = generic_read_dir,
 861        .iterate_shared = proc_sys_readdir,
 862        .llseek         = generic_file_llseek,
 863};
 864
 865static const struct inode_operations proc_sys_inode_operations = {
 866        .permission     = proc_sys_permission,
 867        .setattr        = proc_sys_setattr,
 868        .getattr        = proc_sys_getattr,
 869};
 870
 871static const struct inode_operations proc_sys_dir_operations = {
 872        .lookup         = proc_sys_lookup,
 873        .permission     = proc_sys_permission,
 874        .setattr        = proc_sys_setattr,
 875        .getattr        = proc_sys_getattr,
 876};
 877
 878static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
 879{
 880        if (flags & LOOKUP_RCU)
 881                return -ECHILD;
 882        return !PROC_I(d_inode(dentry))->sysctl->unregistering;
 883}
 884
 885static int proc_sys_delete(const struct dentry *dentry)
 886{
 887        return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
 888}
 889
 890static int sysctl_is_seen(struct ctl_table_header *p)
 891{
 892        struct ctl_table_set *set = p->set;
 893        int res;
 894        spin_lock(&sysctl_lock);
 895        if (p->unregistering)
 896                res = 0;
 897        else if (!set->is_seen)
 898                res = 1;
 899        else
 900                res = set->is_seen(set);
 901        spin_unlock(&sysctl_lock);
 902        return res;
 903}
 904
 905static int proc_sys_compare(const struct dentry *dentry,
 906                unsigned int len, const char *str, const struct qstr *name)
 907{
 908        struct ctl_table_header *head;
 909        struct inode *inode;
 910
 911        /* Although proc doesn't have negative dentries, rcu-walk means
 912         * that inode here can be NULL */
 913        /* AV: can it, indeed? */
 914        inode = d_inode_rcu(dentry);
 915        if (!inode)
 916                return 1;
 917        if (name->len != len)
 918                return 1;
 919        if (memcmp(name->name, str, len))
 920                return 1;
 921        head = rcu_dereference(PROC_I(inode)->sysctl);
 922        return !head || !sysctl_is_seen(head);
 923}
 924
 925static const struct dentry_operations proc_sys_dentry_operations = {
 926        .d_revalidate   = proc_sys_revalidate,
 927        .d_delete       = proc_sys_delete,
 928        .d_compare      = proc_sys_compare,
 929};
 930
 931static struct ctl_dir *find_subdir(struct ctl_dir *dir,
 932                                   const char *name, int namelen)
 933{
 934        struct ctl_table_header *head;
 935        struct ctl_table *entry;
 936
 937        entry = find_entry(&head, dir, name, namelen);
 938        if (!entry)
 939                return ERR_PTR(-ENOENT);
 940        if (!S_ISDIR(entry->mode))
 941                return ERR_PTR(-ENOTDIR);
 942        return container_of(head, struct ctl_dir, header);
 943}
 944
 945static struct ctl_dir *new_dir(struct ctl_table_set *set,
 946                               const char *name, int namelen)
 947{
 948        struct ctl_table *table;
 949        struct ctl_dir *new;
 950        struct ctl_node *node;
 951        char *new_name;
 952
 953        new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
 954                      sizeof(struct ctl_table)*2 +  namelen + 1,
 955                      GFP_KERNEL);
 956        if (!new)
 957                return NULL;
 958
 959        node = (struct ctl_node *)(new + 1);
 960        table = (struct ctl_table *)(node + 1);
 961        new_name = (char *)(table + 2);
 962        memcpy(new_name, name, namelen);
 963        new_name[namelen] = '\0';
 964        table[0].procname = new_name;
 965        table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
 966        init_header(&new->header, set->dir.header.root, set, node, table);
 967
 968        return new;
 969}
 970
 971/**
 972 * get_subdir - find or create a subdir with the specified name.
 973 * @dir:  Directory to create the subdirectory in
 974 * @name: The name of the subdirectory to find or create
 975 * @namelen: The length of name
 976 *
 977 * Takes a directory with an elevated reference count so we know that
 978 * if we drop the lock the directory will not go away.  Upon success
 979 * the reference is moved from @dir to the returned subdirectory.
 980 * Upon error an error code is returned and the reference on @dir is
 981 * simply dropped.
 982 */
 983static struct ctl_dir *get_subdir(struct ctl_dir *dir,
 984                                  const char *name, int namelen)
 985{
 986        struct ctl_table_set *set = dir->header.set;
 987        struct ctl_dir *subdir, *new = NULL;
 988        int err;
 989
 990        spin_lock(&sysctl_lock);
 991        subdir = find_subdir(dir, name, namelen);
 992        if (!IS_ERR(subdir))
 993                goto found;
 994        if (PTR_ERR(subdir) != -ENOENT)
 995                goto failed;
 996
 997        spin_unlock(&sysctl_lock);
 998        new = new_dir(set, name, namelen);
 999        spin_lock(&sysctl_lock);
1000        subdir = ERR_PTR(-ENOMEM);
1001        if (!new)
1002                goto failed;
1003
1004        /* Was the subdir added while we dropped the lock? */
1005        subdir = find_subdir(dir, name, namelen);
1006        if (!IS_ERR(subdir))
1007                goto found;
1008        if (PTR_ERR(subdir) != -ENOENT)
1009                goto failed;
1010
1011        /* Nope.  Use the our freshly made directory entry. */
1012        err = insert_header(dir, &new->header);
1013        subdir = ERR_PTR(err);
1014        if (err)
1015                goto failed;
1016        subdir = new;
1017found:
1018        subdir->header.nreg++;
1019failed:
1020        if (IS_ERR(subdir)) {
1021                pr_err("sysctl could not get directory: ");
1022                sysctl_print_dir(dir);
1023                pr_cont("/%*.*s %ld\n",
1024                        namelen, namelen, name, PTR_ERR(subdir));
1025        }
1026        drop_sysctl_table(&dir->header);
1027        if (new)
1028                drop_sysctl_table(&new->header);
1029        spin_unlock(&sysctl_lock);
1030        return subdir;
1031}
1032
1033static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
1034{
1035        struct ctl_dir *parent;
1036        const char *procname;
1037        if (!dir->header.parent)
1038                return &set->dir;
1039        parent = xlate_dir(set, dir->header.parent);
1040        if (IS_ERR(parent))
1041                return parent;
1042        procname = dir->header.ctl_table[0].procname;
1043        return find_subdir(parent, procname, strlen(procname));
1044}
1045
1046static int sysctl_follow_link(struct ctl_table_header **phead,
1047        struct ctl_table **pentry)
1048{
1049        struct ctl_table_header *head;
1050        struct ctl_table_root *root;
1051        struct ctl_table_set *set;
1052        struct ctl_table *entry;
1053        struct ctl_dir *dir;
1054        int ret;
1055
1056        ret = 0;
1057        spin_lock(&sysctl_lock);
1058        root = (*pentry)->data;
1059        set = lookup_header_set(root);
1060        dir = xlate_dir(set, (*phead)->parent);
1061        if (IS_ERR(dir))
1062                ret = PTR_ERR(dir);
1063        else {
1064                const char *procname = (*pentry)->procname;
1065                head = NULL;
1066                entry = find_entry(&head, dir, procname, strlen(procname));
1067                ret = -ENOENT;
1068                if (entry && use_table(head)) {
1069                        unuse_table(*phead);
1070                        *phead = head;
1071                        *pentry = entry;
1072                        ret = 0;
1073                }
1074        }
1075
1076        spin_unlock(&sysctl_lock);
1077        return ret;
1078}
1079
1080static int sysctl_err(const char *path, struct ctl_table *table, char *fmt, ...)
1081{
1082        struct va_format vaf;
1083        va_list args;
1084
1085        va_start(args, fmt);
1086        vaf.fmt = fmt;
1087        vaf.va = &args;
1088
1089        pr_err("sysctl table check failed: %s/%s %pV\n",
1090               path, table->procname, &vaf);
1091
1092        va_end(args);
1093        return -EINVAL;
1094}
1095
1096static int sysctl_check_table_array(const char *path, struct ctl_table *table)
1097{
1098        int err = 0;
1099
1100        if ((table->proc_handler == proc_douintvec) ||
1101            (table->proc_handler == proc_douintvec_minmax)) {
1102                if (table->maxlen != sizeof(unsigned int))
1103                        err |= sysctl_err(path, table, "array not allowed");
1104        }
1105
1106        if (table->proc_handler == proc_dou8vec_minmax) {
1107                if (table->maxlen != sizeof(u8))
1108                        err |= sysctl_err(path, table, "array not allowed");
1109        }
1110
1111        return err;
1112}
1113
1114static int sysctl_check_table(const char *path, struct ctl_table *table)
1115{
1116        int err = 0;
1117        for (; table->procname; table++) {
1118                if (table->child)
1119                        err |= sysctl_err(path, table, "Not a file");
1120
1121                if ((table->proc_handler == proc_dostring) ||
1122                    (table->proc_handler == proc_dointvec) ||
1123                    (table->proc_handler == proc_douintvec) ||
1124                    (table->proc_handler == proc_douintvec_minmax) ||
1125                    (table->proc_handler == proc_dointvec_minmax) ||
1126                    (table->proc_handler == proc_dou8vec_minmax) ||
1127                    (table->proc_handler == proc_dointvec_jiffies) ||
1128                    (table->proc_handler == proc_dointvec_userhz_jiffies) ||
1129                    (table->proc_handler == proc_dointvec_ms_jiffies) ||
1130                    (table->proc_handler == proc_doulongvec_minmax) ||
1131                    (table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
1132                        if (!table->data)
1133                                err |= sysctl_err(path, table, "No data");
1134                        if (!table->maxlen)
1135                                err |= sysctl_err(path, table, "No maxlen");
1136                        else
1137                                err |= sysctl_check_table_array(path, table);
1138                }
1139                if (!table->proc_handler)
1140                        err |= sysctl_err(path, table, "No proc_handler");
1141
1142                if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
1143                        err |= sysctl_err(path, table, "bogus .mode 0%o",
1144                                table->mode);
1145        }
1146        return err;
1147}
1148
1149static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
1150        struct ctl_table_root *link_root)
1151{
1152        struct ctl_table *link_table, *entry, *link;
1153        struct ctl_table_header *links;
1154        struct ctl_node *node;
1155        char *link_name;
1156        int nr_entries, name_bytes;
1157
1158        name_bytes = 0;
1159        nr_entries = 0;
1160        for (entry = table; entry->procname; entry++) {
1161                nr_entries++;
1162                name_bytes += strlen(entry->procname) + 1;
1163        }
1164
1165        links = kzalloc(sizeof(struct ctl_table_header) +
1166                        sizeof(struct ctl_node)*nr_entries +
1167                        sizeof(struct ctl_table)*(nr_entries + 1) +
1168                        name_bytes,
1169                        GFP_KERNEL);
1170
1171        if (!links)
1172                return NULL;
1173
1174        node = (struct ctl_node *)(links + 1);
1175        link_table = (struct ctl_table *)(node + nr_entries);
1176        link_name = (char *)&link_table[nr_entries + 1];
1177
1178        for (link = link_table, entry = table; entry->procname; link++, entry++) {
1179                int len = strlen(entry->procname) + 1;
1180                memcpy(link_name, entry->procname, len);
1181                link->procname = link_name;
1182                link->mode = S_IFLNK|S_IRWXUGO;
1183                link->data = link_root;
1184                link_name += len;
1185        }
1186        init_header(links, dir->header.root, dir->header.set, node, link_table);
1187        links->nreg = nr_entries;
1188
1189        return links;
1190}
1191
1192static bool get_links(struct ctl_dir *dir,
1193        struct ctl_table *table, struct ctl_table_root *link_root)
1194{
1195        struct ctl_table_header *head;
1196        struct ctl_table *entry, *link;
1197
1198        /* Are there links available for every entry in table? */
1199        for (entry = table; entry->procname; entry++) {
1200                const char *procname = entry->procname;
1201                link = find_entry(&head, dir, procname, strlen(procname));
1202                if (!link)
1203                        return false;
1204                if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
1205                        continue;
1206                if (S_ISLNK(link->mode) && (link->data == link_root))
1207                        continue;
1208                return false;
1209        }
1210
1211        /* The checks passed.  Increase the registration count on the links */
1212        for (entry = table; entry->procname; entry++) {
1213                const char *procname = entry->procname;
1214                link = find_entry(&head, dir, procname, strlen(procname));
1215                head->nreg++;
1216        }
1217        return true;
1218}
1219
1220static int insert_links(struct ctl_table_header *head)
1221{
1222        struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1223        struct ctl_dir *core_parent = NULL;
1224        struct ctl_table_header *links;
1225        int err;
1226
1227        if (head->set == root_set)
1228                return 0;
1229
1230        core_parent = xlate_dir(root_set, head->parent);
1231        if (IS_ERR(core_parent))
1232                return 0;
1233
1234        if (get_links(core_parent, head->ctl_table, head->root))
1235                return 0;
1236
1237        core_parent->header.nreg++;
1238        spin_unlock(&sysctl_lock);
1239
1240        links = new_links(core_parent, head->ctl_table, head->root);
1241
1242        spin_lock(&sysctl_lock);
1243        err = -ENOMEM;
1244        if (!links)
1245                goto out;
1246
1247        err = 0;
1248        if (get_links(core_parent, head->ctl_table, head->root)) {
1249                kfree(links);
1250                goto out;
1251        }
1252
1253        err = insert_header(core_parent, links);
1254        if (err)
1255                kfree(links);
1256out:
1257        drop_sysctl_table(&core_parent->header);
1258        return err;
1259}
1260
1261/**
1262 * __register_sysctl_table - register a leaf sysctl table
1263 * @set: Sysctl tree to register on
1264 * @path: The path to the directory the sysctl table is in.
1265 * @table: the top-level table structure
1266 *
1267 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1268 * array. A completely 0 filled entry terminates the table.
1269 *
1270 * The members of the &struct ctl_table structure are used as follows:
1271 *
1272 * procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
1273 *            enter a sysctl file
1274 *
1275 * data - a pointer to data for use by proc_handler
1276 *
1277 * maxlen - the maximum size in bytes of the data
1278 *
1279 * mode - the file permissions for the /proc/sys file
1280 *
1281 * child - must be %NULL.
1282 *
1283 * proc_handler - the text handler routine (described below)
1284 *
1285 * extra1, extra2 - extra pointers usable by the proc handler routines
1286 *
1287 * Leaf nodes in the sysctl tree will be represented by a single file
1288 * under /proc; non-leaf nodes will be represented by directories.
1289 *
1290 * There must be a proc_handler routine for any terminal nodes.
1291 * Several default handlers are available to cover common cases -
1292 *
1293 * proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
1294 * proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
1295 * proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
1296 *
1297 * It is the handler's job to read the input buffer from user memory
1298 * and process it. The handler should return 0 on success.
1299 *
1300 * This routine returns %NULL on a failure to register, and a pointer
1301 * to the table header on success.
1302 */
1303struct ctl_table_header *__register_sysctl_table(
1304        struct ctl_table_set *set,
1305        const char *path, struct ctl_table *table)
1306{
1307        struct ctl_table_root *root = set->dir.header.root;
1308        struct ctl_table_header *header;
1309        const char *name, *nextname;
1310        struct ctl_dir *dir;
1311        struct ctl_table *entry;
1312        struct ctl_node *node;
1313        int nr_entries = 0;
1314
1315        for (entry = table; entry->procname; entry++)
1316                nr_entries++;
1317
1318        header = kzalloc(sizeof(struct ctl_table_header) +
1319                         sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
1320        if (!header)
1321                return NULL;
1322
1323        node = (struct ctl_node *)(header + 1);
1324        init_header(header, root, set, node, table);
1325        if (sysctl_check_table(path, table))
1326                goto fail;
1327
1328        spin_lock(&sysctl_lock);
1329        dir = &set->dir;
1330        /* Reference moved down the diretory tree get_subdir */
1331        dir->header.nreg++;
1332        spin_unlock(&sysctl_lock);
1333
1334        /* Find the directory for the ctl_table */
1335        for (name = path; name; name = nextname) {
1336                int namelen;
1337                nextname = strchr(name, '/');
1338                if (nextname) {
1339                        namelen = nextname - name;
1340                        nextname++;
1341                } else {
1342                        namelen = strlen(name);
1343                }
1344                if (namelen == 0)
1345                        continue;
1346
1347                dir = get_subdir(dir, name, namelen);
1348                if (IS_ERR(dir))
1349                        goto fail;
1350        }
1351
1352        spin_lock(&sysctl_lock);
1353        if (insert_header(dir, header))
1354                goto fail_put_dir_locked;
1355
1356        drop_sysctl_table(&dir->header);
1357        spin_unlock(&sysctl_lock);
1358
1359        return header;
1360
1361fail_put_dir_locked:
1362        drop_sysctl_table(&dir->header);
1363        spin_unlock(&sysctl_lock);
1364fail:
1365        kfree(header);
1366        dump_stack();
1367        return NULL;
1368}
1369
1370/**
1371 * register_sysctl - register a sysctl table
1372 * @path: The path to the directory the sysctl table is in.
1373 * @table: the table structure
1374 *
1375 * Register a sysctl table. @table should be a filled in ctl_table
1376 * array. A completely 0 filled entry terminates the table.
1377 *
1378 * See __register_sysctl_table for more details.
1379 */
1380struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
1381{
1382        return __register_sysctl_table(&sysctl_table_root.default_set,
1383                                        path, table);
1384}
1385EXPORT_SYMBOL(register_sysctl);
1386
1387static char *append_path(const char *path, char *pos, const char *name)
1388{
1389        int namelen;
1390        namelen = strlen(name);
1391        if (((pos - path) + namelen + 2) >= PATH_MAX)
1392                return NULL;
1393        memcpy(pos, name, namelen);
1394        pos[namelen] = '/';
1395        pos[namelen + 1] = '\0';
1396        pos += namelen + 1;
1397        return pos;
1398}
1399
1400static int count_subheaders(struct ctl_table *table)
1401{
1402        int has_files = 0;
1403        int nr_subheaders = 0;
1404        struct ctl_table *entry;
1405
1406        /* special case: no directory and empty directory */
1407        if (!table || !table->procname)
1408                return 1;
1409
1410        for (entry = table; entry->procname; entry++) {
1411                if (entry->child)
1412                        nr_subheaders += count_subheaders(entry->child);
1413                else
1414                        has_files = 1;
1415        }
1416        return nr_subheaders + has_files;
1417}
1418
1419static int register_leaf_sysctl_tables(const char *path, char *pos,
1420        struct ctl_table_header ***subheader, struct ctl_table_set *set,
1421        struct ctl_table *table)
1422{
1423        struct ctl_table *ctl_table_arg = NULL;
1424        struct ctl_table *entry, *files;
1425        int nr_files = 0;
1426        int nr_dirs = 0;
1427        int err = -ENOMEM;
1428
1429        for (entry = table; entry->procname; entry++) {
1430                if (entry->child)
1431                        nr_dirs++;
1432                else
1433                        nr_files++;
1434        }
1435
1436        files = table;
1437        /* If there are mixed files and directories we need a new table */
1438        if (nr_dirs && nr_files) {
1439                struct ctl_table *new;
1440                files = kcalloc(nr_files + 1, sizeof(struct ctl_table),
1441                                GFP_KERNEL);
1442                if (!files)
1443                        goto out;
1444
1445                ctl_table_arg = files;
1446                for (new = files, entry = table; entry->procname; entry++) {
1447                        if (entry->child)
1448                                continue;
1449                        *new = *entry;
1450                        new++;
1451                }
1452        }
1453
1454        /* Register everything except a directory full of subdirectories */
1455        if (nr_files || !nr_dirs) {
1456                struct ctl_table_header *header;
1457                header = __register_sysctl_table(set, path, files);
1458                if (!header) {
1459                        kfree(ctl_table_arg);
1460                        goto out;
1461                }
1462
1463                /* Remember if we need to free the file table */
1464                header->ctl_table_arg = ctl_table_arg;
1465                **subheader = header;
1466                (*subheader)++;
1467        }
1468
1469        /* Recurse into the subdirectories. */
1470        for (entry = table; entry->procname; entry++) {
1471                char *child_pos;
1472
1473                if (!entry->child)
1474                        continue;
1475
1476                err = -ENAMETOOLONG;
1477                child_pos = append_path(path, pos, entry->procname);
1478                if (!child_pos)
1479                        goto out;
1480
1481                err = register_leaf_sysctl_tables(path, child_pos, subheader,
1482                                                  set, entry->child);
1483                pos[0] = '\0';
1484                if (err)
1485                        goto out;
1486        }
1487        err = 0;
1488out:
1489        /* On failure our caller will unregister all registered subheaders */
1490        return err;
1491}
1492
1493/**
1494 * __register_sysctl_paths - register a sysctl table hierarchy
1495 * @set: Sysctl tree to register on
1496 * @path: The path to the directory the sysctl table is in.
1497 * @table: the top-level table structure
1498 *
1499 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1500 * array. A completely 0 filled entry terminates the table.
1501 *
1502 * See __register_sysctl_table for more details.
1503 */
1504struct ctl_table_header *__register_sysctl_paths(
1505        struct ctl_table_set *set,
1506        const struct ctl_path *path, struct ctl_table *table)
1507{
1508        struct ctl_table *ctl_table_arg = table;
1509        int nr_subheaders = count_subheaders(table);
1510        struct ctl_table_header *header = NULL, **subheaders, **subheader;
1511        const struct ctl_path *component;
1512        char *new_path, *pos;
1513
1514        pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
1515        if (!new_path)
1516                return NULL;
1517
1518        pos[0] = '\0';
1519        for (component = path; component->procname; component++) {
1520                pos = append_path(new_path, pos, component->procname);
1521                if (!pos)
1522                        goto out;
1523        }
1524        while (table->procname && table->child && !table[1].procname) {
1525                pos = append_path(new_path, pos, table->procname);
1526                if (!pos)
1527                        goto out;
1528                table = table->child;
1529        }
1530        if (nr_subheaders == 1) {
1531                header = __register_sysctl_table(set, new_path, table);
1532                if (header)
1533                        header->ctl_table_arg = ctl_table_arg;
1534        } else {
1535                header = kzalloc(sizeof(*header) +
1536                                 sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
1537                if (!header)
1538                        goto out;
1539
1540                subheaders = (struct ctl_table_header **) (header + 1);
1541                subheader = subheaders;
1542                header->ctl_table_arg = ctl_table_arg;
1543
1544                if (register_leaf_sysctl_tables(new_path, pos, &subheader,
1545                                                set, table))
1546                        goto err_register_leaves;
1547        }
1548
1549out:
1550        kfree(new_path);
1551        return header;
1552
1553err_register_leaves:
1554        while (subheader > subheaders) {
1555                struct ctl_table_header *subh = *(--subheader);
1556                struct ctl_table *table = subh->ctl_table_arg;
1557                unregister_sysctl_table(subh);
1558                kfree(table);
1559        }
1560        kfree(header);
1561        header = NULL;
1562        goto out;
1563}
1564
1565/**
1566 * register_sysctl_paths - register a sysctl table hierarchy
1567 * @path: The path to the directory the sysctl table is in.
1568 * @table: the top-level table structure
1569 *
1570 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1571 * array. A completely 0 filled entry terminates the table.
1572 *
1573 * See __register_sysctl_paths for more details.
1574 */
1575struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
1576                                                struct ctl_table *table)
1577{
1578        return __register_sysctl_paths(&sysctl_table_root.default_set,
1579                                        path, table);
1580}
1581EXPORT_SYMBOL(register_sysctl_paths);
1582
1583/**
1584 * register_sysctl_table - register a sysctl table hierarchy
1585 * @table: the top-level table structure
1586 *
1587 * Register a sysctl table hierarchy. @table should be a filled in ctl_table
1588 * array. A completely 0 filled entry terminates the table.
1589 *
1590 * See register_sysctl_paths for more details.
1591 */
1592struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
1593{
1594        static const struct ctl_path null_path[] = { {} };
1595
1596        return register_sysctl_paths(null_path, table);
1597}
1598EXPORT_SYMBOL(register_sysctl_table);
1599
1600static void put_links(struct ctl_table_header *header)
1601{
1602        struct ctl_table_set *root_set = &sysctl_table_root.default_set;
1603        struct ctl_table_root *root = header->root;
1604        struct ctl_dir *parent = header->parent;
1605        struct ctl_dir *core_parent;
1606        struct ctl_table *entry;
1607
1608        if (header->set == root_set)
1609                return;
1610
1611        core_parent = xlate_dir(root_set, parent);
1612        if (IS_ERR(core_parent))
1613                return;
1614
1615        for (entry = header->ctl_table; entry->procname; entry++) {
1616                struct ctl_table_header *link_head;
1617                struct ctl_table *link;
1618                const char *name = entry->procname;
1619
1620                link = find_entry(&link_head, core_parent, name, strlen(name));
1621                if (link &&
1622                    ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
1623                     (S_ISLNK(link->mode) && (link->data == root)))) {
1624                        drop_sysctl_table(link_head);
1625                }
1626                else {
1627                        pr_err("sysctl link missing during unregister: ");
1628                        sysctl_print_dir(parent);
1629                        pr_cont("/%s\n", name);
1630                }
1631        }
1632}
1633
1634static void drop_sysctl_table(struct ctl_table_header *header)
1635{
1636        struct ctl_dir *parent = header->parent;
1637
1638        if (--header->nreg)
1639                return;
1640
1641        if (parent) {
1642                put_links(header);
1643                start_unregistering(header);
1644        }
1645
1646        if (!--header->count)
1647                kfree_rcu(header, rcu);
1648
1649        if (parent)
1650                drop_sysctl_table(&parent->header);
1651}
1652
1653/**
1654 * unregister_sysctl_table - unregister a sysctl table hierarchy
1655 * @header: the header returned from register_sysctl_table
1656 *
1657 * Unregisters the sysctl table and all children. proc entries may not
1658 * actually be removed until they are no longer used by anyone.
1659 */
1660void unregister_sysctl_table(struct ctl_table_header * header)
1661{
1662        int nr_subheaders;
1663        might_sleep();
1664
1665        if (header == NULL)
1666                return;
1667
1668        nr_subheaders = count_subheaders(header->ctl_table_arg);
1669        if (unlikely(nr_subheaders > 1)) {
1670                struct ctl_table_header **subheaders;
1671                int i;
1672
1673                subheaders = (struct ctl_table_header **)(header + 1);
1674                for (i = nr_subheaders -1; i >= 0; i--) {
1675                        struct ctl_table_header *subh = subheaders[i];
1676                        struct ctl_table *table = subh->ctl_table_arg;
1677                        unregister_sysctl_table(subh);
1678                        kfree(table);
1679                }
1680                kfree(header);
1681                return;
1682        }
1683
1684        spin_lock(&sysctl_lock);
1685        drop_sysctl_table(header);
1686        spin_unlock(&sysctl_lock);
1687}
1688EXPORT_SYMBOL(unregister_sysctl_table);
1689
1690void setup_sysctl_set(struct ctl_table_set *set,
1691        struct ctl_table_root *root,
1692        int (*is_seen)(struct ctl_table_set *))
1693{
1694        memset(set, 0, sizeof(*set));
1695        set->is_seen = is_seen;
1696        init_header(&set->dir.header, root, set, NULL, root_table);
1697}
1698
1699void retire_sysctl_set(struct ctl_table_set *set)
1700{
1701        WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
1702}
1703
1704int __init proc_sys_init(void)
1705{
1706        struct proc_dir_entry *proc_sys_root;
1707
1708        proc_sys_root = proc_mkdir("sys", NULL);
1709        proc_sys_root->proc_iops = &proc_sys_dir_operations;
1710        proc_sys_root->proc_dir_ops = &proc_sys_dir_file_operations;
1711        proc_sys_root->nlink = 0;
1712
1713        return sysctl_init();
1714}
1715
1716struct sysctl_alias {
1717        const char *kernel_param;
1718        const char *sysctl_param;
1719};
1720
1721/*
1722 * Historically some settings had both sysctl and a command line parameter.
1723 * With the generic sysctl. parameter support, we can handle them at a single
1724 * place and only keep the historical name for compatibility. This is not meant
1725 * to add brand new aliases. When adding existing aliases, consider whether
1726 * the possibly different moment of changing the value (e.g. from early_param
1727 * to the moment do_sysctl_args() is called) is an issue for the specific
1728 * parameter.
1729 */
1730static const struct sysctl_alias sysctl_aliases[] = {
1731        {"hardlockup_all_cpu_backtrace",        "kernel.hardlockup_all_cpu_backtrace" },
1732        {"hung_task_panic",                     "kernel.hung_task_panic" },
1733        {"numa_zonelist_order",                 "vm.numa_zonelist_order" },
1734        {"softlockup_all_cpu_backtrace",        "kernel.softlockup_all_cpu_backtrace" },
1735        {"softlockup_panic",                    "kernel.softlockup_panic" },
1736        { }
1737};
1738
1739static const char *sysctl_find_alias(char *param)
1740{
1741        const struct sysctl_alias *alias;
1742
1743        for (alias = &sysctl_aliases[0]; alias->kernel_param != NULL; alias++) {
1744                if (strcmp(alias->kernel_param, param) == 0)
1745                        return alias->sysctl_param;
1746        }
1747
1748        return NULL;
1749}
1750
1751/* Set sysctl value passed on kernel command line. */
1752static int process_sysctl_arg(char *param, char *val,
1753                               const char *unused, void *arg)
1754{
1755        char *path;
1756        struct vfsmount **proc_mnt = arg;
1757        struct file_system_type *proc_fs_type;
1758        struct file *file;
1759        int len;
1760        int err;
1761        loff_t pos = 0;
1762        ssize_t wret;
1763
1764        if (strncmp(param, "sysctl", sizeof("sysctl") - 1) == 0) {
1765                param += sizeof("sysctl") - 1;
1766
1767                if (param[0] != '/' && param[0] != '.')
1768                        return 0;
1769
1770                param++;
1771        } else {
1772                param = (char *) sysctl_find_alias(param);
1773                if (!param)
1774                        return 0;
1775        }
1776
1777        if (!val)
1778                return -EINVAL;
1779        len = strlen(val);
1780        if (len == 0)
1781                return -EINVAL;
1782
1783        /*
1784         * To set sysctl options, we use a temporary mount of proc, look up the
1785         * respective sys/ file and write to it. To avoid mounting it when no
1786         * options were given, we mount it only when the first sysctl option is
1787         * found. Why not a persistent mount? There are problems with a
1788         * persistent mount of proc in that it forces userspace not to use any
1789         * proc mount options.
1790         */
1791        if (!*proc_mnt) {
1792                proc_fs_type = get_fs_type("proc");
1793                if (!proc_fs_type) {
1794                        pr_err("Failed to find procfs to set sysctl from command line\n");
1795                        return 0;
1796                }
1797                *proc_mnt = kern_mount(proc_fs_type);
1798                put_filesystem(proc_fs_type);
1799                if (IS_ERR(*proc_mnt)) {
1800                        pr_err("Failed to mount procfs to set sysctl from command line\n");
1801                        return 0;
1802                }
1803        }
1804
1805        path = kasprintf(GFP_KERNEL, "sys/%s", param);
1806        if (!path)
1807                panic("%s: Failed to allocate path for %s\n", __func__, param);
1808        strreplace(path, '.', '/');
1809
1810        file = file_open_root((*proc_mnt)->mnt_root, *proc_mnt, path, O_WRONLY, 0);
1811        if (IS_ERR(file)) {
1812                err = PTR_ERR(file);
1813                if (err == -ENOENT)
1814                        pr_err("Failed to set sysctl parameter '%s=%s': parameter not found\n",
1815                                param, val);
1816                else if (err == -EACCES)
1817                        pr_err("Failed to set sysctl parameter '%s=%s': permission denied (read-only?)\n",
1818                                param, val);
1819                else
1820                        pr_err("Error %pe opening proc file to set sysctl parameter '%s=%s'\n",
1821                                file, param, val);
1822                goto out;
1823        }
1824        wret = kernel_write(file, val, len, &pos);
1825        if (wret < 0) {
1826                err = wret;
1827                if (err == -EINVAL)
1828                        pr_err("Failed to set sysctl parameter '%s=%s': invalid value\n",
1829                                param, val);
1830                else
1831                        pr_err("Error %pe writing to proc file to set sysctl parameter '%s=%s'\n",
1832                                ERR_PTR(err), param, val);
1833        } else if (wret != len) {
1834                pr_err("Wrote only %zd bytes of %d writing to proc file %s to set sysctl parameter '%s=%s\n",
1835                        wret, len, path, param, val);
1836        }
1837
1838        err = filp_close(file, NULL);
1839        if (err)
1840                pr_err("Error %pe closing proc file to set sysctl parameter '%s=%s\n",
1841                        ERR_PTR(err), param, val);
1842out:
1843        kfree(path);
1844        return 0;
1845}
1846
1847void do_sysctl_args(void)
1848{
1849        char *command_line;
1850        struct vfsmount *proc_mnt = NULL;
1851
1852        command_line = kstrdup(saved_command_line, GFP_KERNEL);
1853        if (!command_line)
1854                panic("%s: Failed to allocate copy of command line\n", __func__);
1855
1856        parse_args("Setting sysctl args", command_line,
1857                   NULL, 0, -1, -1, &proc_mnt, process_sysctl_arg);
1858
1859        if (proc_mnt)
1860                kern_unmount(proc_mnt);
1861
1862        kfree(command_line);
1863}
1864