linux/fs/binfmt_misc.c
<<
>>
Prefs
   1/*
   2 *  binfmt_misc.c
   3 *
   4 *  Copyright (C) 1997 Richard G√ľnther
   5 *
   6 *  binfmt_misc detects binaries via a magic or filename extension and invokes
   7 *  a specified wrapper. This should obsolete binfmt_java, binfmt_em86 and
   8 *  binfmt_mz.
   9 *
  10 *  1997-04-25 first version
  11 *  [...]
  12 *  1997-05-19 cleanup
  13 *  1997-06-26 hpa: pass the real filename rather than argv[0]
  14 *  1997-06-30 minor cleanup
  15 *  1997-08-09 removed extension stripping, locking cleanup
  16 *  2001-02-28 AV: rewritten into something that resembles C. Original didn't.
  17 */
  18
  19#include <linux/module.h>
  20#include <linux/init.h>
  21#include <linux/sched.h>
  22#include <linux/magic.h>
  23#include <linux/binfmts.h>
  24#include <linux/slab.h>
  25#include <linux/ctype.h>
  26#include <linux/file.h>
  27#include <linux/pagemap.h>
  28#include <linux/namei.h>
  29#include <linux/mount.h>
  30#include <linux/syscalls.h>
  31#include <linux/fs.h>
  32
  33#include <asm/uaccess.h>
  34
  35enum {
  36        VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
  37};
  38
  39static LIST_HEAD(entries);
  40static int enabled = 1;
  41
  42enum {Enabled, Magic};
  43#define MISC_FMT_PRESERVE_ARGV0 (1<<31)
  44#define MISC_FMT_OPEN_BINARY (1<<30)
  45#define MISC_FMT_CREDENTIALS (1<<29)
  46
  47typedef struct {
  48        struct list_head list;
  49        unsigned long flags;            /* type, status, etc. */
  50        int offset;                     /* offset of magic */
  51        int size;                       /* size of magic/mask */
  52        char *magic;                    /* magic or filename extension */
  53        char *mask;                     /* mask, NULL for exact match */
  54        char *interpreter;              /* filename of interpreter */
  55        char *name;
  56        struct dentry *dentry;
  57} Node;
  58
  59static DEFINE_RWLOCK(entries_lock);
  60static struct file_system_type bm_fs_type;
  61static struct vfsmount *bm_mnt;
  62static int entry_count;
  63
  64/* 
  65 * Check if we support the binfmt
  66 * if we do, return the node, else NULL
  67 * locking is done in load_misc_binary
  68 */
  69static Node *check_file(struct linux_binprm *bprm)
  70{
  71        char *p = strrchr(bprm->interp, '.');
  72        struct list_head *l;
  73
  74        list_for_each(l, &entries) {
  75                Node *e = list_entry(l, Node, list);
  76                char *s;
  77                int j;
  78
  79                if (!test_bit(Enabled, &e->flags))
  80                        continue;
  81
  82                if (!test_bit(Magic, &e->flags)) {
  83                        if (p && !strcmp(e->magic, p + 1))
  84                                return e;
  85                        continue;
  86                }
  87
  88                s = bprm->buf + e->offset;
  89                if (e->mask) {
  90                        for (j = 0; j < e->size; j++)
  91                                if ((*s++ ^ e->magic[j]) & e->mask[j])
  92                                        break;
  93                } else {
  94                        for (j = 0; j < e->size; j++)
  95                                if ((*s++ ^ e->magic[j]))
  96                                        break;
  97                }
  98                if (j == e->size)
  99                        return e;
 100        }
 101        return NULL;
 102}
 103
 104/*
 105 * the loader itself
 106 */
 107static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 108{
 109        Node *fmt;
 110        struct file * interp_file = NULL;
 111        char iname[BINPRM_BUF_SIZE];
 112        const char *iname_addr = iname;
 113        int retval;
 114        int fd_binary = -1;
 115
 116        retval = -ENOEXEC;
 117        if (!enabled)
 118                goto _ret;
 119
 120        retval = -ENOEXEC;
 121        if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
 122                goto _ret;
 123
 124        /* to keep locking time low, we copy the interpreter string */
 125        read_lock(&entries_lock);
 126        fmt = check_file(bprm);
 127        if (fmt)
 128                strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
 129        read_unlock(&entries_lock);
 130        if (!fmt)
 131                goto _ret;
 132
 133        if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
 134                retval = remove_arg_zero(bprm);
 135                if (retval)
 136                        goto _ret;
 137        }
 138
 139        if (fmt->flags & MISC_FMT_OPEN_BINARY) {
 140
 141                /* if the binary should be opened on behalf of the
 142                 * interpreter than keep it open and assign descriptor
 143                 * to it */
 144                fd_binary = get_unused_fd();
 145                if (fd_binary < 0) {
 146                        retval = fd_binary;
 147                        goto _ret;
 148                }
 149                fd_install(fd_binary, bprm->file);
 150
 151                /* if the binary is not readable than enforce mm->dumpable=0
 152                   regardless of the interpreter's permissions */
 153                would_dump(bprm, bprm->file);
 154
 155                allow_write_access(bprm->file);
 156                bprm->file = NULL;
 157
 158                /* mark the bprm that fd should be passed to interp */
 159                bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
 160                bprm->interp_data = fd_binary;
 161
 162        } else {
 163                allow_write_access(bprm->file);
 164                fput(bprm->file);
 165                bprm->file = NULL;
 166        }
 167        /* make argv[1] be the path to the binary */
 168        retval = copy_strings_kernel (1, &bprm->interp, bprm);
 169        if (retval < 0)
 170                goto _error;
 171        bprm->argc++;
 172
 173        /* add the interp as argv[0] */
 174        retval = copy_strings_kernel (1, &iname_addr, bprm);
 175        if (retval < 0)
 176                goto _error;
 177        bprm->argc ++;
 178
 179        bprm->interp = iname;   /* for binfmt_script */
 180
 181        interp_file = open_exec (iname);
 182        retval = PTR_ERR (interp_file);
 183        if (IS_ERR (interp_file))
 184                goto _error;
 185
 186        bprm->file = interp_file;
 187        if (fmt->flags & MISC_FMT_CREDENTIALS) {
 188                /*
 189                 * No need to call prepare_binprm(), it's already been
 190                 * done.  bprm->buf is stale, update from interp_file.
 191                 */
 192                memset(bprm->buf, 0, BINPRM_BUF_SIZE);
 193                retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
 194        } else
 195                retval = prepare_binprm (bprm);
 196
 197        if (retval < 0)
 198                goto _error;
 199
 200        bprm->recursion_depth++;
 201
 202        retval = search_binary_handler (bprm, regs);
 203        if (retval < 0)
 204                goto _error;
 205
 206_ret:
 207        return retval;
 208_error:
 209        if (fd_binary > 0)
 210                sys_close(fd_binary);
 211        bprm->interp_flags = 0;
 212        bprm->interp_data = 0;
 213        goto _ret;
 214}
 215
 216/* Command parsers */
 217
 218/*
 219 * parses and copies one argument enclosed in del from *sp to *dp,
 220 * recognising the \x special.
 221 * returns pointer to the copied argument or NULL in case of an
 222 * error (and sets err) or null argument length.
 223 */
 224static char *scanarg(char *s, char del)
 225{
 226        char c;
 227
 228        while ((c = *s++) != del) {
 229                if (c == '\\' && *s == 'x') {
 230                        s++;
 231                        if (!isxdigit(*s++))
 232                                return NULL;
 233                        if (!isxdigit(*s++))
 234                                return NULL;
 235                }
 236        }
 237        return s;
 238}
 239
 240static int unquote(char *from)
 241{
 242        char c = 0, *s = from, *p = from;
 243
 244        while ((c = *s++) != '\0') {
 245                if (c == '\\' && *s == 'x') {
 246                        s++;
 247                        c = toupper(*s++);
 248                        *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
 249                        c = toupper(*s++);
 250                        *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
 251                        continue;
 252                }
 253                *p++ = c;
 254        }
 255        return p - from;
 256}
 257
 258static char * check_special_flags (char * sfs, Node * e)
 259{
 260        char * p = sfs;
 261        int cont = 1;
 262
 263        /* special flags */
 264        while (cont) {
 265                switch (*p) {
 266                        case 'P':
 267                                p++;
 268                                e->flags |= MISC_FMT_PRESERVE_ARGV0;
 269                                break;
 270                        case 'O':
 271                                p++;
 272                                e->flags |= MISC_FMT_OPEN_BINARY;
 273                                break;
 274                        case 'C':
 275                                p++;
 276                                /* this flags also implies the
 277                                   open-binary flag */
 278                                e->flags |= (MISC_FMT_CREDENTIALS |
 279                                                MISC_FMT_OPEN_BINARY);
 280                                break;
 281                        default:
 282                                cont = 0;
 283                }
 284        }
 285
 286        return p;
 287}
 288/*
 289 * This registers a new binary format, it recognises the syntax
 290 * ':name:type:offset:magic:mask:interpreter:flags'
 291 * where the ':' is the IFS, that can be chosen with the first char
 292 */
 293static Node *create_entry(const char __user *buffer, size_t count)
 294{
 295        Node *e;
 296        int memsize, err;
 297        char *buf, *p;
 298        char del;
 299
 300        /* some sanity checks */
 301        err = -EINVAL;
 302        if ((count < 11) || (count > 256))
 303                goto out;
 304
 305        err = -ENOMEM;
 306        memsize = sizeof(Node) + count + 8;
 307        e = kmalloc(memsize, GFP_USER);
 308        if (!e)
 309                goto out;
 310
 311        p = buf = (char *)e + sizeof(Node);
 312
 313        memset(e, 0, sizeof(Node));
 314        if (copy_from_user(buf, buffer, count))
 315                goto Efault;
 316
 317        del = *p++;     /* delimeter */
 318
 319        memset(buf+count, del, 8);
 320
 321        e->name = p;
 322        p = strchr(p, del);
 323        if (!p)
 324                goto Einval;
 325        *p++ = '\0';
 326        if (!e->name[0] ||
 327            !strcmp(e->name, ".") ||
 328            !strcmp(e->name, "..") ||
 329            strchr(e->name, '/'))
 330                goto Einval;
 331        switch (*p++) {
 332                case 'E': e->flags = 1<<Enabled; break;
 333                case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
 334                default: goto Einval;
 335        }
 336        if (*p++ != del)
 337                goto Einval;
 338        if (test_bit(Magic, &e->flags)) {
 339                char *s = strchr(p, del);
 340                if (!s)
 341                        goto Einval;
 342                *s++ = '\0';
 343                e->offset = simple_strtoul(p, &p, 10);
 344                if (*p++)
 345                        goto Einval;
 346                e->magic = p;
 347                p = scanarg(p, del);
 348                if (!p)
 349                        goto Einval;
 350                p[-1] = '\0';
 351                if (!e->magic[0])
 352                        goto Einval;
 353                e->mask = p;
 354                p = scanarg(p, del);
 355                if (!p)
 356                        goto Einval;
 357                p[-1] = '\0';
 358                if (!e->mask[0])
 359                        e->mask = NULL;
 360                e->size = unquote(e->magic);
 361                if (e->mask && unquote(e->mask) != e->size)
 362                        goto Einval;
 363                if (e->size + e->offset > BINPRM_BUF_SIZE)
 364                        goto Einval;
 365        } else {
 366                p = strchr(p, del);
 367                if (!p)
 368                        goto Einval;
 369                *p++ = '\0';
 370                e->magic = p;
 371                p = strchr(p, del);
 372                if (!p)
 373                        goto Einval;
 374                *p++ = '\0';
 375                if (!e->magic[0] || strchr(e->magic, '/'))
 376                        goto Einval;
 377                p = strchr(p, del);
 378                if (!p)
 379                        goto Einval;
 380                *p++ = '\0';
 381        }
 382        e->interpreter = p;
 383        p = strchr(p, del);
 384        if (!p)
 385                goto Einval;
 386        *p++ = '\0';
 387        if (!e->interpreter[0])
 388                goto Einval;
 389
 390
 391        p = check_special_flags (p, e);
 392
 393        if (*p == '\n')
 394                p++;
 395        if (p != buf + count)
 396                goto Einval;
 397        return e;
 398
 399out:
 400        return ERR_PTR(err);
 401
 402Efault:
 403        kfree(e);
 404        return ERR_PTR(-EFAULT);
 405Einval:
 406        kfree(e);
 407        return ERR_PTR(-EINVAL);
 408}
 409
 410/*
 411 * Set status of entry/binfmt_misc:
 412 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
 413 */
 414static int parse_command(const char __user *buffer, size_t count)
 415{
 416        char s[4];
 417
 418        if (!count)
 419                return 0;
 420        if (count > 3)
 421                return -EINVAL;
 422        if (copy_from_user(s, buffer, count))
 423                return -EFAULT;
 424        if (s[count-1] == '\n')
 425                count--;
 426        if (count == 1 && s[0] == '0')
 427                return 1;
 428        if (count == 1 && s[0] == '1')
 429                return 2;
 430        if (count == 2 && s[0] == '-' && s[1] == '1')
 431                return 3;
 432        return -EINVAL;
 433}
 434
 435/* generic stuff */
 436
 437static void entry_status(Node *e, char *page)
 438{
 439        char *dp;
 440        char *status = "disabled";
 441        const char * flags = "flags: ";
 442
 443        if (test_bit(Enabled, &e->flags))
 444                status = "enabled";
 445
 446        if (!VERBOSE_STATUS) {
 447                sprintf(page, "%s\n", status);
 448                return;
 449        }
 450
 451        sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
 452        dp = page + strlen(page);
 453
 454        /* print the special flags */
 455        sprintf (dp, "%s", flags);
 456        dp += strlen (flags);
 457        if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
 458                *dp ++ = 'P';
 459        }
 460        if (e->flags & MISC_FMT_OPEN_BINARY) {
 461                *dp ++ = 'O';
 462        }
 463        if (e->flags & MISC_FMT_CREDENTIALS) {
 464                *dp ++ = 'C';
 465        }
 466        *dp ++ = '\n';
 467
 468
 469        if (!test_bit(Magic, &e->flags)) {
 470                sprintf(dp, "extension .%s\n", e->magic);
 471        } else {
 472                int i;
 473
 474                sprintf(dp, "offset %i\nmagic ", e->offset);
 475                dp = page + strlen(page);
 476                for (i = 0; i < e->size; i++) {
 477                        sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
 478                        dp += 2;
 479                }
 480                if (e->mask) {
 481                        sprintf(dp, "\nmask ");
 482                        dp += 6;
 483                        for (i = 0; i < e->size; i++) {
 484                                sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
 485                                dp += 2;
 486                        }
 487                }
 488                *dp++ = '\n';
 489                *dp = '\0';
 490        }
 491}
 492
 493static struct inode *bm_get_inode(struct super_block *sb, int mode)
 494{
 495        struct inode * inode = new_inode(sb);
 496
 497        if (inode) {
 498                inode->i_ino = get_next_ino();
 499                inode->i_mode = mode;
 500                inode->i_atime = inode->i_mtime = inode->i_ctime =
 501                        current_fs_time(inode->i_sb);
 502        }
 503        return inode;
 504}
 505
 506static void bm_evict_inode(struct inode *inode)
 507{
 508        clear_inode(inode);
 509        kfree(inode->i_private);
 510}
 511
 512static void kill_node(Node *e)
 513{
 514        struct dentry *dentry;
 515
 516        write_lock(&entries_lock);
 517        dentry = e->dentry;
 518        if (dentry) {
 519                list_del_init(&e->list);
 520                e->dentry = NULL;
 521        }
 522        write_unlock(&entries_lock);
 523
 524        if (dentry) {
 525                drop_nlink(dentry->d_inode);
 526                d_drop(dentry);
 527                dput(dentry);
 528                simple_release_fs(&bm_mnt, &entry_count);
 529        }
 530}
 531
 532/* /<entry> */
 533
 534static ssize_t
 535bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
 536{
 537        Node *e = file->f_path.dentry->d_inode->i_private;
 538        ssize_t res;
 539        char *page;
 540
 541        if (!(page = (char*) __get_free_page(GFP_KERNEL)))
 542                return -ENOMEM;
 543
 544        entry_status(e, page);
 545
 546        res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
 547
 548        free_page((unsigned long) page);
 549        return res;
 550}
 551
 552static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
 553                                size_t count, loff_t *ppos)
 554{
 555        struct dentry *root;
 556        Node *e = file->f_path.dentry->d_inode->i_private;
 557        int res = parse_command(buffer, count);
 558
 559        switch (res) {
 560                case 1: clear_bit(Enabled, &e->flags);
 561                        break;
 562                case 2: set_bit(Enabled, &e->flags);
 563                        break;
 564                case 3: root = dget(file->f_path.dentry->d_sb->s_root);
 565                        mutex_lock(&root->d_inode->i_mutex);
 566
 567                        kill_node(e);
 568
 569                        mutex_unlock(&root->d_inode->i_mutex);
 570                        dput(root);
 571                        break;
 572                default: return res;
 573        }
 574        return count;
 575}
 576
 577static const struct file_operations bm_entry_operations = {
 578        .read           = bm_entry_read,
 579        .write          = bm_entry_write,
 580        .llseek         = default_llseek,
 581};
 582
 583/* /register */
 584
 585static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 586                               size_t count, loff_t *ppos)
 587{
 588        Node *e;
 589        struct inode *inode;
 590        struct dentry *root, *dentry;
 591        struct super_block *sb = file->f_path.dentry->d_sb;
 592        int err = 0;
 593
 594        e = create_entry(buffer, count);
 595
 596        if (IS_ERR(e))
 597                return PTR_ERR(e);
 598
 599        root = dget(sb->s_root);
 600        mutex_lock(&root->d_inode->i_mutex);
 601        dentry = lookup_one_len(e->name, root, strlen(e->name));
 602        err = PTR_ERR(dentry);
 603        if (IS_ERR(dentry))
 604                goto out;
 605
 606        err = -EEXIST;
 607        if (dentry->d_inode)
 608                goto out2;
 609
 610        inode = bm_get_inode(sb, S_IFREG | 0644);
 611
 612        err = -ENOMEM;
 613        if (!inode)
 614                goto out2;
 615
 616        err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
 617        if (err) {
 618                iput(inode);
 619                inode = NULL;
 620                goto out2;
 621        }
 622
 623        e->dentry = dget(dentry);
 624        inode->i_private = e;
 625        inode->i_fop = &bm_entry_operations;
 626
 627        d_instantiate(dentry, inode);
 628        write_lock(&entries_lock);
 629        list_add(&e->list, &entries);
 630        write_unlock(&entries_lock);
 631
 632        err = 0;
 633out2:
 634        dput(dentry);
 635out:
 636        mutex_unlock(&root->d_inode->i_mutex);
 637        dput(root);
 638
 639        if (err) {
 640                kfree(e);
 641                return -EINVAL;
 642        }
 643        return count;
 644}
 645
 646static const struct file_operations bm_register_operations = {
 647        .write          = bm_register_write,
 648        .llseek         = noop_llseek,
 649};
 650
 651/* /status */
 652
 653static ssize_t
 654bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
 655{
 656        char *s = enabled ? "enabled\n" : "disabled\n";
 657
 658        return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
 659}
 660
 661static ssize_t bm_status_write(struct file * file, const char __user * buffer,
 662                size_t count, loff_t *ppos)
 663{
 664        int res = parse_command(buffer, count);
 665        struct dentry *root;
 666
 667        switch (res) {
 668                case 1: enabled = 0; break;
 669                case 2: enabled = 1; break;
 670                case 3: root = dget(file->f_path.dentry->d_sb->s_root);
 671                        mutex_lock(&root->d_inode->i_mutex);
 672
 673                        while (!list_empty(&entries))
 674                                kill_node(list_entry(entries.next, Node, list));
 675
 676                        mutex_unlock(&root->d_inode->i_mutex);
 677                        dput(root);
 678                default: return res;
 679        }
 680        return count;
 681}
 682
 683static const struct file_operations bm_status_operations = {
 684        .read           = bm_status_read,
 685        .write          = bm_status_write,
 686        .llseek         = default_llseek,
 687};
 688
 689/* Superblock handling */
 690
 691static const struct super_operations s_ops = {
 692        .statfs         = simple_statfs,
 693        .evict_inode    = bm_evict_inode,
 694};
 695
 696static int bm_fill_super(struct super_block * sb, void * data, int silent)
 697{
 698        static struct tree_descr bm_files[] = {
 699                [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
 700                [3] = {"register", &bm_register_operations, S_IWUSR},
 701                /* last one */ {""}
 702        };
 703        int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
 704        if (!err)
 705                sb->s_op = &s_ops;
 706        return err;
 707}
 708
 709static struct dentry *bm_mount(struct file_system_type *fs_type,
 710        int flags, const char *dev_name, void *data)
 711{
 712        return mount_single(fs_type, flags, data, bm_fill_super);
 713}
 714
 715static struct linux_binfmt misc_format = {
 716        .module = THIS_MODULE,
 717        .load_binary = load_misc_binary,
 718};
 719
 720static struct file_system_type bm_fs_type = {
 721        .owner          = THIS_MODULE,
 722        .name           = "binfmt_misc",
 723        .mount          = bm_mount,
 724        .kill_sb        = kill_litter_super,
 725};
 726
 727static int __init init_misc_binfmt(void)
 728{
 729        int err = register_filesystem(&bm_fs_type);
 730        if (!err)
 731                insert_binfmt(&misc_format);
 732        return err;
 733}
 734
 735static void __exit exit_misc_binfmt(void)
 736{
 737        unregister_binfmt(&misc_format);
 738        unregister_filesystem(&bm_fs_type);
 739}
 740
 741core_initcall(init_misc_binfmt);
 742module_exit(exit_misc_binfmt);
 743MODULE_LICENSE("GPL");
 744
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.