kernel/kmod.c

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