linux/kernel/kmod.c
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   1/*
   2        kmod, the new module loader (replaces kerneld)
   3        Kirk Petersen
   4
   5        Reorganized not to be a daemon by Adam Richter, with guidance
   6        from Greg Zornetzer.
   7
   8        Modified to avoid chroot and file sharing problems.
   9        Mikael Pettersson
  10
  11        Limit the concurrent number of kmod modprobes to catch loops from
  12        "modprobe needs a service that is in a module".
  13        Keith Owens <kaos@ocs.com.au> December 1999
  14
  15        Unblock all signals when we exec a usermode process.
  16        Shuu Yamaguchi <shuu@wondernetworkresources.com> December 2000
  17
  18        call_usermodehelper wait flag, and remove exec_usermodehelper.
  19        Rusty Russell <rusty@rustcorp.com.au>  Jan 2003
  20*/
  21#include <linux/module.h>
  22#include <linux/sched.h>
  23#include <linux/syscalls.h>
  24#include <linux/unistd.h>
  25#include <linux/kmod.h>
  26#include <linux/slab.h>
  27#include <linux/completion.h>
  28#include <linux/cred.h>
  29#include <linux/file.h>
  30#include <linux/fdtable.h>
  31#include <linux/workqueue.h>
  32#include <linux/security.h>
  33#include <linux/mount.h>
  34#include <linux/kernel.h>
  35#include <linux/init.h>
  36#include <linux/resource.h>
  37#include <linux/notifier.h>
  38#include <linux/suspend.h>
  39#include <linux/rwsem.h>
  40#include <linux/ptrace.h>
  41#include <linux/async.h>
  42#include <asm/uaccess.h>
  43
  44#include <trace/events/module.h>
  45
  46extern int max_threads;
  47
  48static struct workqueue_struct *khelper_wq;
  49
  50/*
  51 * kmod_thread_locker is used for deadlock avoidance.  There is no explicit
  52 * locking to protect this global - it is private to the singleton khelper
  53 * thread and should only ever be modified by that thread.
  54 */
  55static const struct task_struct *kmod_thread_locker;
  56
  57#define CAP_BSET        (void *)1
  58#define CAP_PI          (void *)2
  59
  60static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
  61static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
  62static DEFINE_SPINLOCK(umh_sysctl_lock);
  63static DECLARE_RWSEM(umhelper_sem);
  64
  65#ifdef CONFIG_MODULES
  66
  67/*
  68        modprobe_path is set via /proc/sys.
  69*/
  70char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
  71
  72static void free_modprobe_argv(struct subprocess_info *info)
  73{
  74        kfree(info->argv[3]); /* check call_modprobe() */
  75        kfree(info->argv);
  76}
  77
  78static int call_modprobe(char *module_name, int wait)
  79{
  80        static char *envp[] = {
  81                "HOME=/",
  82                "TERM=linux",
  83                "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
  84                NULL
  85        };
  86
  87        char **argv = kmalloc(sizeof(char *[5]), GFP_KERNEL);
  88        if (!argv)
  89                goto out;
  90
  91        module_name = kstrdup(module_name, GFP_KERNEL);
  92        if (!module_name)
  93                goto free_argv;
  94
  95        argv[0] = modprobe_path;
  96        argv[1] = "-q";
  97        argv[2] = "--";
  98        argv[3] = module_name;  /* check free_modprobe_argv() */
  99        argv[4] = NULL;
 100
 101        return call_usermodehelper_fns(modprobe_path, argv, envp,
 102                wait | UMH_KILLABLE, NULL, free_modprobe_argv, NULL);
 103free_argv:
 104        kfree(argv);
 105out:
 106        return -ENOMEM;
 107}
 108
 109/**
 110 * __request_module - try to load a kernel module
 111 * @wait: wait (or not) for the operation to complete
 112 * @fmt: printf style format string for the name of the module
 113 * @...: arguments as specified in the format string
 114 *
 115 * Load a module using the user mode module loader. The function returns
 116 * zero on success or a negative errno code on failure. Note that a
 117 * successful module load does not mean the module did not then unload
 118 * and exit on an error of its own. Callers must check that the service
 119 * they requested is now available not blindly invoke it.
 120 *
 121 * If module auto-loading support is disabled then this function
 122 * becomes a no-operation.
 123 */
 124int __request_module(bool wait, const char *fmt, ...)
 125{
 126        va_list args;
 127        char module_name[MODULE_NAME_LEN];
 128        unsigned int max_modprobes;
 129        int ret;
 130        static atomic_t kmod_concurrent = ATOMIC_INIT(0);
 131#define MAX_KMOD_CONCURRENT 50  /* Completely arbitrary value - KAO */
 132        static int kmod_loop_msg;
 133
 134        /*
 135         * We don't allow synchronous module loading from async.  Module
 136         * init may invoke async_synchronize_full() which will end up
 137         * waiting for this task which already is waiting for the module
 138         * loading to complete, leading to a deadlock.
 139         */
 140        WARN_ON_ONCE(wait && current_is_async());
 141
 142        va_start(args, fmt);
 143        ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
 144        va_end(args);
 145        if (ret >= MODULE_NAME_LEN)
 146                return -ENAMETOOLONG;
 147
 148        ret = security_kernel_module_request(module_name);
 149        if (ret)
 150                return ret;
 151
 152        /* If modprobe needs a service that is in a module, we get a recursive
 153         * loop.  Limit the number of running kmod threads to max_threads/2 or
 154         * MAX_KMOD_CONCURRENT, whichever is the smaller.  A cleaner method
 155         * would be to run the parents of this process, counting how many times
 156         * kmod was invoked.  That would mean accessing the internals of the
 157         * process tables to get the command line, proc_pid_cmdline is static
 158         * and it is not worth changing the proc code just to handle this case. 
 159         * KAO.
 160         *
 161         * "trace the ppid" is simple, but will fail if someone's
 162         * parent exits.  I think this is as good as it gets. --RR
 163         */
 164        max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT);
 165        atomic_inc(&kmod_concurrent);
 166        if (atomic_read(&kmod_concurrent) > max_modprobes) {
 167                /* We may be blaming an innocent here, but unlikely */
 168                if (kmod_loop_msg < 5) {
 169                        printk(KERN_ERR
 170                               "request_module: runaway loop modprobe %s\n",
 171                               module_name);
 172                        kmod_loop_msg++;
 173                }
 174                atomic_dec(&kmod_concurrent);
 175                return -ENOMEM;
 176        }
 177
 178        trace_module_request(module_name, wait, _RET_IP_);
 179
 180        ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
 181
 182        atomic_dec(&kmod_concurrent);
 183        return ret;
 184}
 185EXPORT_SYMBOL(__request_module);
 186#endif /* CONFIG_MODULES */
 187
 188/*
 189 * This is the task which runs the usermode application
 190 */
 191static int ____call_usermodehelper(void *data)
 192{
 193        struct subprocess_info *sub_info = data;
 194        struct cred *new;
 195        int retval;
 196
 197        spin_lock_irq(&current->sighand->siglock);
 198        flush_signal_handlers(current, 1);
 199        spin_unlock_irq(&current->sighand->siglock);
 200
 201        /* We can run anywhere, unlike our parent keventd(). */
 202        set_cpus_allowed_ptr(current, cpu_all_mask);
 203
 204        /*
 205         * Our parent is keventd, which runs with elevated scheduling priority.
 206         * Avoid propagating that into the userspace child.
 207         */
 208        set_user_nice(current, 0);
 209
 210        retval = -ENOMEM;
 211        new = prepare_kernel_cred(current);
 212        if (!new)
 213                goto fail;
 214
 215        spin_lock(&umh_sysctl_lock);
 216        new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
 217        new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
 218                                             new->cap_inheritable);
 219        spin_unlock(&umh_sysctl_lock);
 220
 221        if (sub_info->init) {
 222                retval = sub_info->init(sub_info, new);
 223                if (retval) {
 224                        abort_creds(new);
 225                        goto fail;
 226                }
 227        }
 228
 229        commit_creds(new);
 230
 231        retval = do_execve(sub_info->path,
 232                           (const char __user *const __user *)sub_info->argv,
 233                           (const char __user *const __user *)sub_info->envp);
 234        if (!retval)
 235                return 0;
 236
 237        /* Exec failed? */
 238fail:
 239        sub_info->retval = retval;
 240        do_exit(0);
 241}
 242
 243static int call_helper(void *data)
 244{
 245        /* Worker thread started blocking khelper thread. */
 246        kmod_thread_locker = current;
 247        return ____call_usermodehelper(data);
 248}
 249
 250static void call_usermodehelper_freeinfo(struct subprocess_info *info)
 251{
 252        if (info->cleanup)
 253                (*info->cleanup)(info);
 254        kfree(info);
 255}
 256
 257static void umh_complete(struct subprocess_info *sub_info)
 258{
 259        struct completion *comp = xchg(&sub_info->complete, NULL);
 260        /*
 261         * See call_usermodehelper_exec(). If xchg() returns NULL
 262         * we own sub_info, the UMH_KILLABLE caller has gone away.
 263         */
 264        if (comp)
 265                complete(comp);
 266        else
 267                call_usermodehelper_freeinfo(sub_info);
 268}
 269
 270/* Keventd can't block, but this (a child) can. */
 271static int wait_for_helper(void *data)
 272{
 273        struct subprocess_info *sub_info = data;
 274        pid_t pid;
 275
 276        /* If SIGCLD is ignored sys_wait4 won't populate the status. */
 277        spin_lock_irq(&current->sighand->siglock);
 278        current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
 279        spin_unlock_irq(&current->sighand->siglock);
 280
 281        pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
 282        if (pid < 0) {
 283                sub_info->retval = pid;
 284        } else {
 285                int ret = -ECHILD;
 286                /*
 287                 * Normally it is bogus to call wait4() from in-kernel because
 288                 * wait4() wants to write the exit code to a userspace address.
 289                 * But wait_for_helper() always runs as keventd, and put_user()
 290                 * to a kernel address works OK for kernel threads, due to their
 291                 * having an mm_segment_t which spans the entire address space.
 292                 *
 293                 * Thus the __user pointer cast is valid here.
 294                 */
 295                sys_wait4(pid, (int __user *)&ret, 0, NULL);
 296
 297                /*
 298                 * If ret is 0, either ____call_usermodehelper failed and the
 299                 * real error code is already in sub_info->retval or
 300                 * sub_info->retval is 0 anyway, so don't mess with it then.
 301                 */
 302                if (ret)
 303                        sub_info->retval = ret;
 304        }
 305
 306        umh_complete(sub_info);
 307        do_exit(0);
 308}
 309
 310/* This is run by khelper thread  */
 311static void __call_usermodehelper(struct work_struct *work)
 312{
 313        struct subprocess_info *sub_info =
 314                container_of(work, struct subprocess_info, work);
 315        int wait = sub_info->wait & ~UMH_KILLABLE;
 316        pid_t pid;
 317
 318        /* CLONE_VFORK: wait until the usermode helper has execve'd
 319         * successfully We need the data structures to stay around
 320         * until that is done.  */
 321        if (wait == UMH_WAIT_PROC)
 322                pid = kernel_thread(wait_for_helper, sub_info,
 323                                    CLONE_FS | CLONE_FILES | SIGCHLD);
 324        else {
 325                pid = kernel_thread(call_helper, sub_info,
 326                                    CLONE_VFORK | SIGCHLD);
 327                /* Worker thread stopped blocking khelper thread. */
 328                kmod_thread_locker = NULL;
 329        }
 330
 331        switch (wait) {
 332        case UMH_NO_WAIT:
 333                call_usermodehelper_freeinfo(sub_info);
 334                break;
 335
 336        case UMH_WAIT_PROC:
 337                if (pid > 0)
 338                        break;
 339                /* FALLTHROUGH */
 340        case UMH_WAIT_EXEC:
 341                if (pid < 0)
 342                        sub_info->retval = pid;
 343                umh_complete(sub_info);
 344        }
 345}
 346
 347/*
 348 * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
 349 * (used for preventing user land processes from being created after the user
 350 * land has been frozen during a system-wide hibernation or suspend operation).
 351 * Should always be manipulated under umhelper_sem acquired for write.
 352 */
 353static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 354
 355/* Number of helpers running */
 356static atomic_t running_helpers = ATOMIC_INIT(0);
 357
 358/*
 359 * Wait queue head used by usermodehelper_disable() to wait for all running
 360 * helpers to finish.
 361 */
 362static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
 363
 364/*
 365 * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
 366 * to become 'false'.
 367 */
 368static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 369
 370/*
 371 * Time to wait for running_helpers to become zero before the setting of
 372 * usermodehelper_disabled in usermodehelper_disable() fails
 373 */
 374#define RUNNING_HELPERS_TIMEOUT (5 * HZ)
 375
 376int usermodehelper_read_trylock(void)
 377{
 378        DEFINE_WAIT(wait);
 379        int ret = 0;
 380
 381        down_read(&umhelper_sem);
 382        for (;;) {
 383                prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 384                                TASK_INTERRUPTIBLE);
 385                if (!usermodehelper_disabled)
 386                        break;
 387
 388                if (usermodehelper_disabled == UMH_DISABLED)
 389                        ret = -EAGAIN;
 390
 391                up_read(&umhelper_sem);
 392
 393                if (ret)
 394                        break;
 395
 396                schedule();
 397                try_to_freeze();
 398
 399                down_read(&umhelper_sem);
 400        }
 401        finish_wait(&usermodehelper_disabled_waitq, &wait);
 402        return ret;
 403}
 404EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
 405
 406long usermodehelper_read_lock_wait(long timeout)
 407{
 408        DEFINE_WAIT(wait);
 409
 410        if (timeout < 0)
 411                return -EINVAL;
 412
 413        down_read(&umhelper_sem);
 414        for (;;) {
 415                prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 416                                TASK_UNINTERRUPTIBLE);
 417                if (!usermodehelper_disabled)
 418                        break;
 419
 420                up_read(&umhelper_sem);
 421
 422                timeout = schedule_timeout(timeout);
 423                if (!timeout)
 424                        break;
 425
 426                down_read(&umhelper_sem);
 427        }
 428        finish_wait(&usermodehelper_disabled_waitq, &wait);
 429        return timeout;
 430}
 431EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
 432
 433void usermodehelper_read_unlock(void)
 434{
 435        up_read(&umhelper_sem);
 436}
 437EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 438
 439/**
 440 * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
 441 * @depth: New value to assign to usermodehelper_disabled.
 442 *
 443 * Change the value of usermodehelper_disabled (under umhelper_sem locked for
 444 * writing) and wakeup tasks waiting for it to change.
 445 */
 446void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 447{
 448        down_write(&umhelper_sem);
 449        usermodehelper_disabled = depth;
 450        wake_up(&usermodehelper_disabled_waitq);
 451        up_write(&umhelper_sem);
 452}
 453
 454/**
 455 * __usermodehelper_disable - Prevent new helpers from being started.
 456 * @depth: New value to assign to usermodehelper_disabled.
 457 *
 458 * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
 459 */
 460int __usermodehelper_disable(enum umh_disable_depth depth)
 461{
 462        long retval;
 463
 464        if (!depth)
 465                return -EINVAL;
 466
 467        down_write(&umhelper_sem);
 468        usermodehelper_disabled = depth;
 469        up_write(&umhelper_sem);
 470
 471        /*
 472         * From now on call_usermodehelper_exec() won't start any new
 473         * helpers, so it is sufficient if running_helpers turns out to
 474         * be zero at one point (it may be increased later, but that
 475         * doesn't matter).
 476         */
 477        retval = wait_event_timeout(running_helpers_waitq,
 478                                        atomic_read(&running_helpers) == 0,
 479                                        RUNNING_HELPERS_TIMEOUT);
 480        if (retval)
 481                return 0;
 482
 483        __usermodehelper_set_disable_depth(UMH_ENABLED);
 484        return -EAGAIN;
 485}
 486
 487static void helper_lock(void)
 488{
 489        atomic_inc(&running_helpers);
 490        smp_mb__after_atomic_inc();
 491}
 492
 493static void helper_unlock(void)
 494{
 495        if (atomic_dec_and_test(&running_helpers))
 496                wake_up(&running_helpers_waitq);
 497}
 498
 499/**
 500 * call_usermodehelper_setup - prepare to call a usermode helper
 501 * @path: path to usermode executable
 502 * @argv: arg vector for process
 503 * @envp: environment for process
 504 * @gfp_mask: gfp mask for memory allocation
 505 *
 506 * Returns either %NULL on allocation failure, or a subprocess_info
 507 * structure.  This should be passed to call_usermodehelper_exec to
 508 * exec the process and free the structure.
 509 */
 510static
 511struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
 512                                                  char **envp, gfp_t gfp_mask)
 513{
 514        struct subprocess_info *sub_info;
 515        sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
 516        if (!sub_info)
 517                goto out;
 518
 519        INIT_WORK(&sub_info->work, __call_usermodehelper);
 520        sub_info->path = path;
 521        sub_info->argv = argv;
 522        sub_info->envp = envp;
 523  out:
 524        return sub_info;
 525}
 526
 527/**
 528 * call_usermodehelper_setfns - set a cleanup/init function
 529 * @info: a subprocess_info returned by call_usermodehelper_setup
 530 * @cleanup: a cleanup function
 531 * @init: an init function
 532 * @data: arbitrary context sensitive data
 533 *
 534 * The init function is used to customize the helper process prior to
 535 * exec.  A non-zero return code causes the process to error out, exit,
 536 * and return the failure to the calling process
 537 *
 538 * The cleanup function is just before ethe subprocess_info is about to
 539 * be freed.  This can be used for freeing the argv and envp.  The
 540 * Function must be runnable in either a process context or the
 541 * context in which call_usermodehelper_exec is called.
 542 */
 543static
 544void call_usermodehelper_setfns(struct subprocess_info *info,
 545                    int (*init)(struct subprocess_info *info, struct cred *new),
 546                    void (*cleanup)(struct subprocess_info *info),
 547                    void *data)
 548{
 549        info->cleanup = cleanup;
 550        info->init = init;
 551        info->data = data;
 552}
 553
 554/**
 555 * call_usermodehelper_exec - start a usermode application
 556 * @sub_info: information about the subprocessa
 557 * @wait: wait for the application to finish and return status.
 558 *        when -1 don't wait at all, but you get no useful error back when
 559 *        the program couldn't be exec'ed. This makes it safe to call
 560 *        from interrupt context.
 561 *
 562 * Runs a user-space application.  The application is started
 563 * asynchronously if wait is not set, and runs as a child of keventd.
 564 * (ie. it runs with full root capabilities).
 565 */
 566static
 567int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 568{
 569        DECLARE_COMPLETION_ONSTACK(done);
 570        int retval = 0;
 571
 572        helper_lock();
 573        if (!sub_info->path) {
 574                retval = -EINVAL;
 575                goto out;
 576        }
 577
 578        if (sub_info->path[0] == '\0')
 579                goto out;
 580
 581        if (!khelper_wq || usermodehelper_disabled) {
 582                retval = -EBUSY;
 583                goto out;
 584        }
 585        /*
 586         * Worker thread must not wait for khelper thread at below
 587         * wait_for_completion() if the thread was created with CLONE_VFORK
 588         * flag, for khelper thread is already waiting for the thread at
 589         * wait_for_completion() in do_fork().
 590         */
 591        if (wait != UMH_NO_WAIT && current == kmod_thread_locker) {
 592                retval = -EBUSY;
 593                goto out;
 594        }
 595
 596        sub_info->complete = &done;
 597        sub_info->wait = wait;
 598
 599        queue_work(khelper_wq, &sub_info->work);
 600        if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 601                goto unlock;
 602
 603        if (wait & UMH_KILLABLE) {
 604                retval = wait_for_completion_killable(&done);
 605                if (!retval)
 606                        goto wait_done;
 607
 608                /* umh_complete() will see NULL and free sub_info */
 609                if (xchg(&sub_info->complete, NULL))
 610                        goto unlock;
 611                /* fallthrough, umh_complete() was already called */
 612        }
 613
 614        wait_for_completion(&done);
 615wait_done:
 616        retval = sub_info->retval;
 617out:
 618        call_usermodehelper_freeinfo(sub_info);
 619unlock:
 620        helper_unlock();
 621        return retval;
 622}
 623
 624/*
 625 * call_usermodehelper_fns() will not run the caller-provided cleanup function
 626 * if a memory allocation failure is experienced.  So the caller might need to
 627 * check the call_usermodehelper_fns() return value: if it is -ENOMEM, perform
 628 * the necessaary cleanup within the caller.
 629 */
 630int call_usermodehelper_fns(
 631        char *path, char **argv, char **envp, int wait,
 632        int (*init)(struct subprocess_info *info, struct cred *new),
 633        void (*cleanup)(struct subprocess_info *), void *data)
 634{
 635        struct subprocess_info *info;
 636        gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 637
 638        info = call_usermodehelper_setup(path, argv, envp, gfp_mask);
 639
 640        if (info == NULL)
 641                return -ENOMEM;
 642
 643        call_usermodehelper_setfns(info, init, cleanup, data);
 644
 645        return call_usermodehelper_exec(info, wait);
 646}
 647EXPORT_SYMBOL(call_usermodehelper_fns);
 648
 649static int proc_cap_handler(struct ctl_table *table, int write,
 650                         void __user *buffer, size_t *lenp, loff_t *ppos)
 651{
 652        struct ctl_table t;
 653        unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
 654        kernel_cap_t new_cap;
 655        int err, i;
 656
 657        if (write && (!capable(CAP_SETPCAP) ||
 658                      !capable(CAP_SYS_MODULE)))
 659                return -EPERM;
 660
 661        /*
 662         * convert from the global kernel_cap_t to the ulong array to print to
 663         * userspace if this is a read.
 664         */
 665        spin_lock(&umh_sysctl_lock);
 666        for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
 667                if (table->data == CAP_BSET)
 668                        cap_array[i] = usermodehelper_bset.cap[i];
 669                else if (table->data == CAP_PI)
 670                        cap_array[i] = usermodehelper_inheritable.cap[i];
 671                else
 672                        BUG();
 673        }
 674        spin_unlock(&umh_sysctl_lock);
 675
 676        t = *table;
 677        t.data = &cap_array;
 678
 679        /*
 680         * actually read or write and array of ulongs from userspace.  Remember
 681         * these are least significant 32 bits first
 682         */
 683        err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
 684        if (err < 0)
 685                return err;
 686
 687        /*
 688         * convert from the sysctl array of ulongs to the kernel_cap_t
 689         * internal representation
 690         */
 691        for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
 692                new_cap.cap[i] = cap_array[i];
 693
 694        /*
 695         * Drop everything not in the new_cap (but don't add things)
 696         */
 697        spin_lock(&umh_sysctl_lock);
 698        if (write) {
 699                if (table->data == CAP_BSET)
 700                        usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 701                if (table->data == CAP_PI)
 702                        usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
 703        }
 704        spin_unlock(&umh_sysctl_lock);
 705
 706        return 0;
 707}
 708
 709struct ctl_table usermodehelper_table[] = {
 710        {
 711                .procname       = "bset",
 712                .data           = CAP_BSET,
 713                .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 714                .mode           = 0600,
 715                .proc_handler   = proc_cap_handler,
 716        },
 717        {
 718                .procname       = "inheritable",
 719                .data           = CAP_PI,
 720                .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 721                .mode           = 0600,
 722                .proc_handler   = proc_cap_handler,
 723        },
 724        { }
 725};
 726
 727void __init usermodehelper_init(void)
 728{
 729        khelper_wq = create_singlethread_workqueue("khelper");
 730        BUG_ON(!khelper_wq);
 731}
 732
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