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