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