linux/fs/binfmt_misc.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * binfmt_misc.c
   4 *
   5 * Copyright (C) 1997 Richard G√ľnther
   6 *
   7 * binfmt_misc detects binaries via a magic or filename extension and invokes
   8 * a specified wrapper. See Documentation/admin-guide/binfmt-misc.rst for more details.
   9 */
  10
  11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  12
  13#include <linux/kernel.h>
  14#include <linux/module.h>
  15#include <linux/init.h>
  16#include <linux/sched/mm.h>
  17#include <linux/magic.h>
  18#include <linux/binfmts.h>
  19#include <linux/slab.h>
  20#include <linux/ctype.h>
  21#include <linux/string_helpers.h>
  22#include <linux/file.h>
  23#include <linux/pagemap.h>
  24#include <linux/namei.h>
  25#include <linux/mount.h>
  26#include <linux/fs_context.h>
  27#include <linux/syscalls.h>
  28#include <linux/fs.h>
  29#include <linux/uaccess.h>
  30
  31#include "internal.h"
  32
  33#ifdef DEBUG
  34# define USE_DEBUG 1
  35#else
  36# define USE_DEBUG 0
  37#endif
  38
  39enum {
  40        VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
  41};
  42
  43static LIST_HEAD(entries);
  44static int enabled = 1;
  45
  46enum {Enabled, Magic};
  47#define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
  48#define MISC_FMT_OPEN_BINARY (1 << 30)
  49#define MISC_FMT_CREDENTIALS (1 << 29)
  50#define MISC_FMT_OPEN_FILE (1 << 28)
  51
  52typedef struct {
  53        struct list_head list;
  54        unsigned long flags;            /* type, status, etc. */
  55        int offset;                     /* offset of magic */
  56        int size;                       /* size of magic/mask */
  57        char *magic;                    /* magic or filename extension */
  58        char *mask;                     /* mask, NULL for exact match */
  59        const char *interpreter;        /* filename of interpreter */
  60        char *name;
  61        struct dentry *dentry;
  62        struct file *interp_file;
  63} Node;
  64
  65static DEFINE_RWLOCK(entries_lock);
  66static struct file_system_type bm_fs_type;
  67static struct vfsmount *bm_mnt;
  68static int entry_count;
  69
  70/*
  71 * Max length of the register string.  Determined by:
  72 *  - 7 delimiters
  73 *  - name:   ~50 bytes
  74 *  - type:   1 byte
  75 *  - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
  76 *  - magic:  128 bytes (512 in escaped form)
  77 *  - mask:   128 bytes (512 in escaped form)
  78 *  - interp: ~50 bytes
  79 *  - flags:  5 bytes
  80 * Round that up a bit, and then back off to hold the internal data
  81 * (like struct Node).
  82 */
  83#define MAX_REGISTER_LENGTH 1920
  84
  85/*
  86 * Check if we support the binfmt
  87 * if we do, return the node, else NULL
  88 * locking is done in load_misc_binary
  89 */
  90static Node *check_file(struct linux_binprm *bprm)
  91{
  92        char *p = strrchr(bprm->interp, '.');
  93        struct list_head *l;
  94
  95        /* Walk all the registered handlers. */
  96        list_for_each(l, &entries) {
  97                Node *e = list_entry(l, Node, list);
  98                char *s;
  99                int j;
 100
 101                /* Make sure this one is currently enabled. */
 102                if (!test_bit(Enabled, &e->flags))
 103                        continue;
 104
 105                /* Do matching based on extension if applicable. */
 106                if (!test_bit(Magic, &e->flags)) {
 107                        if (p && !strcmp(e->magic, p + 1))
 108                                return e;
 109                        continue;
 110                }
 111
 112                /* Do matching based on magic & mask. */
 113                s = bprm->buf + e->offset;
 114                if (e->mask) {
 115                        for (j = 0; j < e->size; j++)
 116                                if ((*s++ ^ e->magic[j]) & e->mask[j])
 117                                        break;
 118                } else {
 119                        for (j = 0; j < e->size; j++)
 120                                if ((*s++ ^ e->magic[j]))
 121                                        break;
 122                }
 123                if (j == e->size)
 124                        return e;
 125        }
 126        return NULL;
 127}
 128
 129/*
 130 * the loader itself
 131 */
 132static int load_misc_binary(struct linux_binprm *bprm)
 133{
 134        Node *fmt;
 135        struct file *interp_file = NULL;
 136        int retval;
 137
 138        retval = -ENOEXEC;
 139        if (!enabled)
 140                return retval;
 141
 142        /* to keep locking time low, we copy the interpreter string */
 143        read_lock(&entries_lock);
 144        fmt = check_file(bprm);
 145        if (fmt)
 146                dget(fmt->dentry);
 147        read_unlock(&entries_lock);
 148        if (!fmt)
 149                return retval;
 150
 151        /* Need to be able to load the file after exec */
 152        retval = -ENOENT;
 153        if (bprm->interp_flags & BINPRM_FLAGS_PATH_INACCESSIBLE)
 154                goto ret;
 155
 156        if (fmt->flags & MISC_FMT_PRESERVE_ARGV0) {
 157                bprm->interp_flags |= BINPRM_FLAGS_PRESERVE_ARGV0;
 158        } else {
 159                retval = remove_arg_zero(bprm);
 160                if (retval)
 161                        goto ret;
 162        }
 163
 164        if (fmt->flags & MISC_FMT_OPEN_BINARY)
 165                bprm->have_execfd = 1;
 166
 167        /* make argv[1] be the path to the binary */
 168        retval = copy_string_kernel(bprm->interp, bprm);
 169        if (retval < 0)
 170                goto ret;
 171        bprm->argc++;
 172
 173        /* add the interp as argv[0] */
 174        retval = copy_string_kernel(fmt->interpreter, bprm);
 175        if (retval < 0)
 176                goto ret;
 177        bprm->argc++;
 178
 179        /* Update interp in case binfmt_script needs it. */
 180        retval = bprm_change_interp(fmt->interpreter, bprm);
 181        if (retval < 0)
 182                goto ret;
 183
 184        if (fmt->flags & MISC_FMT_OPEN_FILE) {
 185                interp_file = file_clone_open(fmt->interp_file);
 186                if (!IS_ERR(interp_file))
 187                        deny_write_access(interp_file);
 188        } else {
 189                interp_file = open_exec(fmt->interpreter);
 190        }
 191        retval = PTR_ERR(interp_file);
 192        if (IS_ERR(interp_file))
 193                goto ret;
 194
 195        bprm->interpreter = interp_file;
 196        if (fmt->flags & MISC_FMT_CREDENTIALS)
 197                bprm->execfd_creds = 1;
 198
 199        retval = 0;
 200ret:
 201        dput(fmt->dentry);
 202        return retval;
 203}
 204
 205/* Command parsers */
 206
 207/*
 208 * parses and copies one argument enclosed in del from *sp to *dp,
 209 * recognising the \x special.
 210 * returns pointer to the copied argument or NULL in case of an
 211 * error (and sets err) or null argument length.
 212 */
 213static char *scanarg(char *s, char del)
 214{
 215        char c;
 216
 217        while ((c = *s++) != del) {
 218                if (c == '\\' && *s == 'x') {
 219                        s++;
 220                        if (!isxdigit(*s++))
 221                                return NULL;
 222                        if (!isxdigit(*s++))
 223                                return NULL;
 224                }
 225        }
 226        s[-1] ='\0';
 227        return s;
 228}
 229
 230static char *check_special_flags(char *sfs, Node *e)
 231{
 232        char *p = sfs;
 233        int cont = 1;
 234
 235        /* special flags */
 236        while (cont) {
 237                switch (*p) {
 238                case 'P':
 239                        pr_debug("register: flag: P (preserve argv0)\n");
 240                        p++;
 241                        e->flags |= MISC_FMT_PRESERVE_ARGV0;
 242                        break;
 243                case 'O':
 244                        pr_debug("register: flag: O (open binary)\n");
 245                        p++;
 246                        e->flags |= MISC_FMT_OPEN_BINARY;
 247                        break;
 248                case 'C':
 249                        pr_debug("register: flag: C (preserve creds)\n");
 250                        p++;
 251                        /* this flags also implies the
 252                           open-binary flag */
 253                        e->flags |= (MISC_FMT_CREDENTIALS |
 254                                        MISC_FMT_OPEN_BINARY);
 255                        break;
 256                case 'F':
 257                        pr_debug("register: flag: F: open interpreter file now\n");
 258                        p++;
 259                        e->flags |= MISC_FMT_OPEN_FILE;
 260                        break;
 261                default:
 262                        cont = 0;
 263                }
 264        }
 265
 266        return p;
 267}
 268
 269/*
 270 * This registers a new binary format, it recognises the syntax
 271 * ':name:type:offset:magic:mask:interpreter:flags'
 272 * where the ':' is the IFS, that can be chosen with the first char
 273 */
 274static Node *create_entry(const char __user *buffer, size_t count)
 275{
 276        Node *e;
 277        int memsize, err;
 278        char *buf, *p;
 279        char del;
 280
 281        pr_debug("register: received %zu bytes\n", count);
 282
 283        /* some sanity checks */
 284        err = -EINVAL;
 285        if ((count < 11) || (count > MAX_REGISTER_LENGTH))
 286                goto out;
 287
 288        err = -ENOMEM;
 289        memsize = sizeof(Node) + count + 8;
 290        e = kmalloc(memsize, GFP_KERNEL);
 291        if (!e)
 292                goto out;
 293
 294        p = buf = (char *)e + sizeof(Node);
 295
 296        memset(e, 0, sizeof(Node));
 297        if (copy_from_user(buf, buffer, count))
 298                goto efault;
 299
 300        del = *p++;     /* delimeter */
 301
 302        pr_debug("register: delim: %#x {%c}\n", del, del);
 303
 304        /* Pad the buffer with the delim to simplify parsing below. */
 305        memset(buf + count, del, 8);
 306
 307        /* Parse the 'name' field. */
 308        e->name = p;
 309        p = strchr(p, del);
 310        if (!p)
 311                goto einval;
 312        *p++ = '\0';
 313        if (!e->name[0] ||
 314            !strcmp(e->name, ".") ||
 315            !strcmp(e->name, "..") ||
 316            strchr(e->name, '/'))
 317                goto einval;
 318
 319        pr_debug("register: name: {%s}\n", e->name);
 320
 321        /* Parse the 'type' field. */
 322        switch (*p++) {
 323        case 'E':
 324                pr_debug("register: type: E (extension)\n");
 325                e->flags = 1 << Enabled;
 326                break;
 327        case 'M':
 328                pr_debug("register: type: M (magic)\n");
 329                e->flags = (1 << Enabled) | (1 << Magic);
 330                break;
 331        default:
 332                goto einval;
 333        }
 334        if (*p++ != del)
 335                goto einval;
 336
 337        if (test_bit(Magic, &e->flags)) {
 338                /* Handle the 'M' (magic) format. */
 339                char *s;
 340
 341                /* Parse the 'offset' field. */
 342                s = strchr(p, del);
 343                if (!s)
 344                        goto einval;
 345                *s = '\0';
 346                if (p != s) {
 347                        int r = kstrtoint(p, 10, &e->offset);
 348                        if (r != 0 || e->offset < 0)
 349                                goto einval;
 350                }
 351                p = s;
 352                if (*p++)
 353                        goto einval;
 354                pr_debug("register: offset: %#x\n", e->offset);
 355
 356                /* Parse the 'magic' field. */
 357                e->magic = p;
 358                p = scanarg(p, del);
 359                if (!p)
 360                        goto einval;
 361                if (!e->magic[0])
 362                        goto einval;
 363                if (USE_DEBUG)
 364                        print_hex_dump_bytes(
 365                                KBUILD_MODNAME ": register: magic[raw]: ",
 366                                DUMP_PREFIX_NONE, e->magic, p - e->magic);
 367
 368                /* Parse the 'mask' field. */
 369                e->mask = p;
 370                p = scanarg(p, del);
 371                if (!p)
 372                        goto einval;
 373                if (!e->mask[0]) {
 374                        e->mask = NULL;
 375                        pr_debug("register:  mask[raw]: none\n");
 376                } else if (USE_DEBUG)
 377                        print_hex_dump_bytes(
 378                                KBUILD_MODNAME ": register:  mask[raw]: ",
 379                                DUMP_PREFIX_NONE, e->mask, p - e->mask);
 380
 381                /*
 382                 * Decode the magic & mask fields.
 383                 * Note: while we might have accepted embedded NUL bytes from
 384                 * above, the unescape helpers here will stop at the first one
 385                 * it encounters.
 386                 */
 387                e->size = string_unescape_inplace(e->magic, UNESCAPE_HEX);
 388                if (e->mask &&
 389                    string_unescape_inplace(e->mask, UNESCAPE_HEX) != e->size)
 390                        goto einval;
 391                if (e->size > BINPRM_BUF_SIZE ||
 392                    BINPRM_BUF_SIZE - e->size < e->offset)
 393                        goto einval;
 394                pr_debug("register: magic/mask length: %i\n", e->size);
 395                if (USE_DEBUG) {
 396                        print_hex_dump_bytes(
 397                                KBUILD_MODNAME ": register: magic[decoded]: ",
 398                                DUMP_PREFIX_NONE, e->magic, e->size);
 399
 400                        if (e->mask) {
 401                                int i;
 402                                char *masked = kmalloc(e->size, GFP_KERNEL);
 403
 404                                print_hex_dump_bytes(
 405                                        KBUILD_MODNAME ": register:  mask[decoded]: ",
 406                                        DUMP_PREFIX_NONE, e->mask, e->size);
 407
 408                                if (masked) {
 409                                        for (i = 0; i < e->size; ++i)
 410                                                masked[i] = e->magic[i] & e->mask[i];
 411                                        print_hex_dump_bytes(
 412                                                KBUILD_MODNAME ": register:  magic[masked]: ",
 413                                                DUMP_PREFIX_NONE, masked, e->size);
 414
 415                                        kfree(masked);
 416                                }
 417                        }
 418                }
 419        } else {
 420                /* Handle the 'E' (extension) format. */
 421
 422                /* Skip the 'offset' field. */
 423                p = strchr(p, del);
 424                if (!p)
 425                        goto einval;
 426                *p++ = '\0';
 427
 428                /* Parse the 'magic' field. */
 429                e->magic = p;
 430                p = strchr(p, del);
 431                if (!p)
 432                        goto einval;
 433                *p++ = '\0';
 434                if (!e->magic[0] || strchr(e->magic, '/'))
 435                        goto einval;
 436                pr_debug("register: extension: {%s}\n", e->magic);
 437
 438                /* Skip the 'mask' field. */
 439                p = strchr(p, del);
 440                if (!p)
 441                        goto einval;
 442                *p++ = '\0';
 443        }
 444
 445        /* Parse the 'interpreter' field. */
 446        e->interpreter = p;
 447        p = strchr(p, del);
 448        if (!p)
 449                goto einval;
 450        *p++ = '\0';
 451        if (!e->interpreter[0])
 452                goto einval;
 453        pr_debug("register: interpreter: {%s}\n", e->interpreter);
 454
 455        /* Parse the 'flags' field. */
 456        p = check_special_flags(p, e);
 457        if (*p == '\n')
 458                p++;
 459        if (p != buf + count)
 460                goto einval;
 461
 462        return e;
 463
 464out:
 465        return ERR_PTR(err);
 466
 467efault:
 468        kfree(e);
 469        return ERR_PTR(-EFAULT);
 470einval:
 471        kfree(e);
 472        return ERR_PTR(-EINVAL);
 473}
 474
 475/*
 476 * Set status of entry/binfmt_misc:
 477 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
 478 */
 479static int parse_command(const char __user *buffer, size_t count)
 480{
 481        char s[4];
 482
 483        if (count > 3)
 484                return -EINVAL;
 485        if (copy_from_user(s, buffer, count))
 486                return -EFAULT;
 487        if (!count)
 488                return 0;
 489        if (s[count - 1] == '\n')
 490                count--;
 491        if (count == 1 && s[0] == '0')
 492                return 1;
 493        if (count == 1 && s[0] == '1')
 494                return 2;
 495        if (count == 2 && s[0] == '-' && s[1] == '1')
 496                return 3;
 497        return -EINVAL;
 498}
 499
 500/* generic stuff */
 501
 502static void entry_status(Node *e, char *page)
 503{
 504        char *dp = page;
 505        const char *status = "disabled";
 506
 507        if (test_bit(Enabled, &e->flags))
 508                status = "enabled";
 509
 510        if (!VERBOSE_STATUS) {
 511                sprintf(page, "%s\n", status);
 512                return;
 513        }
 514
 515        dp += sprintf(dp, "%s\ninterpreter %s\n", status, e->interpreter);
 516
 517        /* print the special flags */
 518        dp += sprintf(dp, "flags: ");
 519        if (e->flags & MISC_FMT_PRESERVE_ARGV0)
 520                *dp++ = 'P';
 521        if (e->flags & MISC_FMT_OPEN_BINARY)
 522                *dp++ = 'O';
 523        if (e->flags & MISC_FMT_CREDENTIALS)
 524                *dp++ = 'C';
 525        if (e->flags & MISC_FMT_OPEN_FILE)
 526                *dp++ = 'F';
 527        *dp++ = '\n';
 528
 529        if (!test_bit(Magic, &e->flags)) {
 530                sprintf(dp, "extension .%s\n", e->magic);
 531        } else {
 532                dp += sprintf(dp, "offset %i\nmagic ", e->offset);
 533                dp = bin2hex(dp, e->magic, e->size);
 534                if (e->mask) {
 535                        dp += sprintf(dp, "\nmask ");
 536                        dp = bin2hex(dp, e->mask, e->size);
 537                }
 538                *dp++ = '\n';
 539                *dp = '\0';
 540        }
 541}
 542
 543static struct inode *bm_get_inode(struct super_block *sb, int mode)
 544{
 545        struct inode *inode = new_inode(sb);
 546
 547        if (inode) {
 548                inode->i_ino = get_next_ino();
 549                inode->i_mode = mode;
 550                inode->i_atime = inode->i_mtime = inode->i_ctime =
 551                        current_time(inode);
 552        }
 553        return inode;
 554}
 555
 556static void bm_evict_inode(struct inode *inode)
 557{
 558        Node *e = inode->i_private;
 559
 560        if (e && e->flags & MISC_FMT_OPEN_FILE)
 561                filp_close(e->interp_file, NULL);
 562
 563        clear_inode(inode);
 564        kfree(e);
 565}
 566
 567static void kill_node(Node *e)
 568{
 569        struct dentry *dentry;
 570
 571        write_lock(&entries_lock);
 572        list_del_init(&e->list);
 573        write_unlock(&entries_lock);
 574
 575        dentry = e->dentry;
 576        drop_nlink(d_inode(dentry));
 577        d_drop(dentry);
 578        dput(dentry);
 579        simple_release_fs(&bm_mnt, &entry_count);
 580}
 581
 582/* /<entry> */
 583
 584static ssize_t
 585bm_entry_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 586{
 587        Node *e = file_inode(file)->i_private;
 588        ssize_t res;
 589        char *page;
 590
 591        page = (char *) __get_free_page(GFP_KERNEL);
 592        if (!page)
 593                return -ENOMEM;
 594
 595        entry_status(e, page);
 596
 597        res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
 598
 599        free_page((unsigned long) page);
 600        return res;
 601}
 602
 603static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
 604                                size_t count, loff_t *ppos)
 605{
 606        struct dentry *root;
 607        Node *e = file_inode(file)->i_private;
 608        int res = parse_command(buffer, count);
 609
 610        switch (res) {
 611        case 1:
 612                /* Disable this handler. */
 613                clear_bit(Enabled, &e->flags);
 614                break;
 615        case 2:
 616                /* Enable this handler. */
 617                set_bit(Enabled, &e->flags);
 618                break;
 619        case 3:
 620                /* Delete this handler. */
 621                root = file_inode(file)->i_sb->s_root;
 622                inode_lock(d_inode(root));
 623
 624                if (!list_empty(&e->list))
 625                        kill_node(e);
 626
 627                inode_unlock(d_inode(root));
 628                break;
 629        default:
 630                return res;
 631        }
 632
 633        return count;
 634}
 635
 636static const struct file_operations bm_entry_operations = {
 637        .read           = bm_entry_read,
 638        .write          = bm_entry_write,
 639        .llseek         = default_llseek,
 640};
 641
 642/* /register */
 643
 644static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 645                               size_t count, loff_t *ppos)
 646{
 647        Node *e;
 648        struct inode *inode;
 649        struct super_block *sb = file_inode(file)->i_sb;
 650        struct dentry *root = sb->s_root, *dentry;
 651        int err = 0;
 652        struct file *f = NULL;
 653
 654        e = create_entry(buffer, count);
 655
 656        if (IS_ERR(e))
 657                return PTR_ERR(e);
 658
 659        if (e->flags & MISC_FMT_OPEN_FILE) {
 660                f = open_exec(e->interpreter);
 661                if (IS_ERR(f)) {
 662                        pr_notice("register: failed to install interpreter file %s\n",
 663                                 e->interpreter);
 664                        kfree(e);
 665                        return PTR_ERR(f);
 666                }
 667                e->interp_file = f;
 668        }
 669
 670        inode_lock(d_inode(root));
 671        dentry = lookup_one_len(e->name, root, strlen(e->name));
 672        err = PTR_ERR(dentry);
 673        if (IS_ERR(dentry))
 674                goto out;
 675
 676        err = -EEXIST;
 677        if (d_really_is_positive(dentry))
 678                goto out2;
 679
 680        inode = bm_get_inode(sb, S_IFREG | 0644);
 681
 682        err = -ENOMEM;
 683        if (!inode)
 684                goto out2;
 685
 686        err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
 687        if (err) {
 688                iput(inode);
 689                inode = NULL;
 690                goto out2;
 691        }
 692
 693        e->dentry = dget(dentry);
 694        inode->i_private = e;
 695        inode->i_fop = &bm_entry_operations;
 696
 697        d_instantiate(dentry, inode);
 698        write_lock(&entries_lock);
 699        list_add(&e->list, &entries);
 700        write_unlock(&entries_lock);
 701
 702        err = 0;
 703out2:
 704        dput(dentry);
 705out:
 706        inode_unlock(d_inode(root));
 707
 708        if (err) {
 709                if (f)
 710                        filp_close(f, NULL);
 711                kfree(e);
 712                return err;
 713        }
 714        return count;
 715}
 716
 717static const struct file_operations bm_register_operations = {
 718        .write          = bm_register_write,
 719        .llseek         = noop_llseek,
 720};
 721
 722/* /status */
 723
 724static ssize_t
 725bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 726{
 727        char *s = enabled ? "enabled\n" : "disabled\n";
 728
 729        return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
 730}
 731
 732static ssize_t bm_status_write(struct file *file, const char __user *buffer,
 733                size_t count, loff_t *ppos)
 734{
 735        int res = parse_command(buffer, count);
 736        struct dentry *root;
 737
 738        switch (res) {
 739        case 1:
 740                /* Disable all handlers. */
 741                enabled = 0;
 742                break;
 743        case 2:
 744                /* Enable all handlers. */
 745                enabled = 1;
 746                break;
 747        case 3:
 748                /* Delete all handlers. */
 749                root = file_inode(file)->i_sb->s_root;
 750                inode_lock(d_inode(root));
 751
 752                while (!list_empty(&entries))
 753                        kill_node(list_first_entry(&entries, Node, list));
 754
 755                inode_unlock(d_inode(root));
 756                break;
 757        default:
 758                return res;
 759        }
 760
 761        return count;
 762}
 763
 764static const struct file_operations bm_status_operations = {
 765        .read           = bm_status_read,
 766        .write          = bm_status_write,
 767        .llseek         = default_llseek,
 768};
 769
 770/* Superblock handling */
 771
 772static const struct super_operations s_ops = {
 773        .statfs         = simple_statfs,
 774        .evict_inode    = bm_evict_inode,
 775};
 776
 777static int bm_fill_super(struct super_block *sb, struct fs_context *fc)
 778{
 779        int err;
 780        static const struct tree_descr bm_files[] = {
 781                [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
 782                [3] = {"register", &bm_register_operations, S_IWUSR},
 783                /* last one */ {""}
 784        };
 785
 786        err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
 787        if (!err)
 788                sb->s_op = &s_ops;
 789        return err;
 790}
 791
 792static int bm_get_tree(struct fs_context *fc)
 793{
 794        return get_tree_single(fc, bm_fill_super);
 795}
 796
 797static const struct fs_context_operations bm_context_ops = {
 798        .get_tree       = bm_get_tree,
 799};
 800
 801static int bm_init_fs_context(struct fs_context *fc)
 802{
 803        fc->ops = &bm_context_ops;
 804        return 0;
 805}
 806
 807static struct linux_binfmt misc_format = {
 808        .module = THIS_MODULE,
 809        .load_binary = load_misc_binary,
 810};
 811
 812static struct file_system_type bm_fs_type = {
 813        .owner          = THIS_MODULE,
 814        .name           = "binfmt_misc",
 815        .init_fs_context = bm_init_fs_context,
 816        .kill_sb        = kill_litter_super,
 817};
 818MODULE_ALIAS_FS("binfmt_misc");
 819
 820static int __init init_misc_binfmt(void)
 821{
 822        int err = register_filesystem(&bm_fs_type);
 823        if (!err)
 824                insert_binfmt(&misc_format);
 825        return err;
 826}
 827
 828static void __exit exit_misc_binfmt(void)
 829{
 830        unregister_binfmt(&misc_format);
 831        unregister_filesystem(&bm_fs_type);
 832}
 833
 834core_initcall(init_misc_binfmt);
 835module_exit(exit_misc_binfmt);
 836MODULE_LICENSE("GPL");
 837
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