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 /*
  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  */
  55 static const struct task_struct *kmod_thread_locker;
  56
  57 #define CAP_BSET        (void *)1
  58 #define CAP_PI          (void *)2
  59
  60 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
  61 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
  62 static DEFINE_SPINLOCK(umh_sysctl_lock);
  63 static DECLARE_RWSEM(umhelper_sem);
  64
  65 #ifdef CONFIG_MODULES
  66
  67 /*
  68         modprobe_path is set via /proc/sys.
  69 */
  70 char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
  71
  72 static void free_modprobe_argv(struct subprocess_info *info)
  73 {
  74         kfree(info->argv[3]); /* check call_modprobe() */
  75         kfree(info->argv);
  76 }
  77
  78 static 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
 109 free_module_name:
 110         kfree(module_name);
 111 free_argv:
 112         kfree(argv);
 113 out:
 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  */
 132 int __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 }
 196 EXPORT_SYMBOL(__request_module);
 197 #endif /* CONFIG_MODULES */
 198
 199 /*
 200  * This is the task which runs the usermode application
 201  */
 202 static 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(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? */
 249 fail:
 250         sub_info->retval = retval;
 251         do_exit(0);
 252 }
 253
 254 static 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
 261 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
 262 {
 263         if (info->cleanup)
 264                 (*info->cleanup)(info);
 265         kfree(info);
 266 }
 267
 268 static 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. */
 282 static 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         spin_lock_irq(&current->sighand->siglock);
 289         current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL;
 290         spin_unlock_irq(&current->sighand->siglock);
 291
 292         pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD);
 293         if (pid < 0) {
 294                 sub_info->retval = pid;
 295         } else {
 296                 int ret = -ECHILD;
 297                 /*
 298                  * Normally it is bogus to call wait4() from in-kernel because
 299                  * wait4() wants to write the exit code to a userspace address.
 300                  * But wait_for_helper() always runs as keventd, and put_user()
 301                  * to a kernel address works OK for kernel threads, due to their
 302                  * having an mm_segment_t which spans the entire address space.
 303                  *
 304                  * Thus the __user pointer cast is valid here.
 305                  */
 306                 sys_wait4(pid, (int __user *)&ret, 0, NULL);
 307
 308                 /*
 309                  * If ret is 0, either ____call_usermodehelper failed and the
 310                  * real error code is already in sub_info->retval or
 311                  * sub_info->retval is 0 anyway, so don't mess with it then.
 312                  */
 313                 if (ret)
 314                         sub_info->retval = ret;
 315         }
 316
 317         umh_complete(sub_info);
 318         do_exit(0);
 319 }
 320
 321 /* This is run by khelper thread  */
 322 static void __call_usermodehelper(struct work_struct *work)
 323 {
 324         struct subprocess_info *sub_info =
 325                 container_of(work, struct subprocess_info, work);
 326         int wait = sub_info->wait & ~UMH_KILLABLE;
 327         pid_t pid;
 328
 329         /* CLONE_VFORK: wait until the usermode helper has execve'd
 330          * successfully We need the data structures to stay around
 331          * until that is done.  */
 332         if (wait == UMH_WAIT_PROC)
 333                 pid = kernel_thread(wait_for_helper, sub_info,
 334                                     CLONE_FS | CLONE_FILES | SIGCHLD);
 335         else {
 336                 pid = kernel_thread(call_helper, sub_info,
 337                                     CLONE_VFORK | SIGCHLD);
 338                 /* Worker thread stopped blocking khelper thread. */
 339                 kmod_thread_locker = NULL;
 340         }
 341
 342         switch (wait) {
 343         case UMH_NO_WAIT:
 344                 call_usermodehelper_freeinfo(sub_info);
 345                 break;
 346
 347         case UMH_WAIT_PROC:
 348                 if (pid > 0)
 349                         break;
 350                 /* FALLTHROUGH */
 351         case UMH_WAIT_EXEC:
 352                 if (pid < 0)
 353                         sub_info->retval = pid;
 354                 umh_complete(sub_info);
 355         }
 356 }
 357
 358 /*
 359  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
 360  * (used for preventing user land processes from being created after the user
 361  * land has been frozen during a system-wide hibernation or suspend operation).
 362  * Should always be manipulated under umhelper_sem acquired for write.
 363  */
 364 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 365
 366 /* Number of helpers running */
 367 static atomic_t running_helpers = ATOMIC_INIT(0);
 368
 369 /*
 370  * Wait queue head used by usermodehelper_disable() to wait for all running
 371  * helpers to finish.
 372  */
 373 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
 374
 375 /*
 376  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
 377  * to become 'false'.
 378  */
 379 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 380
 381 /*
 382  * Time to wait for running_helpers to become zero before the setting of
 383  * usermodehelper_disabled in usermodehelper_disable() fails
 384  */
 385 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
 386
 387 int usermodehelper_read_trylock(void)
 388 {
 389         DEFINE_WAIT(wait);
 390         int ret = 0;
 391
 392         down_read(&umhelper_sem);
 393         for (;;) {
 394                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 395                                 TASK_INTERRUPTIBLE);
 396                 if (!usermodehelper_disabled)
 397                         break;
 398
 399                 if (usermodehelper_disabled == UMH_DISABLED)
 400                         ret = -EAGAIN;
 401
 402                 up_read(&umhelper_sem);
 403
 404                 if (ret)
 405                         break;
 406
 407                 schedule();
 408                 try_to_freeze();
 409
 410                 down_read(&umhelper_sem);
 411         }
 412         finish_wait(&usermodehelper_disabled_waitq, &wait);
 413         return ret;
 414 }
 415 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
 416
 417 long usermodehelper_read_lock_wait(long timeout)
 418 {
 419         DEFINE_WAIT(wait);
 420
 421         if (timeout < 0)
 422                 return -EINVAL;
 423
 424         down_read(&umhelper_sem);
 425         for (;;) {
 426                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 427                                 TASK_UNINTERRUPTIBLE);
 428                 if (!usermodehelper_disabled)
 429                         break;
 430
 431                 up_read(&umhelper_sem);
 432
 433                 timeout = schedule_timeout(timeout);
 434                 if (!timeout)
 435                         break;
 436
 437                 down_read(&umhelper_sem);
 438         }
 439         finish_wait(&usermodehelper_disabled_waitq, &wait);
 440         return timeout;
 441 }
 442 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
 443
 444 void usermodehelper_read_unlock(void)
 445 {
 446         up_read(&umhelper_sem);
 447 }
 448 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 449
 450 /**
 451  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
 452  * @depth: New value to assign to usermodehelper_disabled.
 453  *
 454  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
 455  * writing) and wakeup tasks waiting for it to change.
 456  */
 457 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 458 {
 459         down_write(&umhelper_sem);
 460         usermodehelper_disabled = depth;
 461         wake_up(&usermodehelper_disabled_waitq);
 462         up_write(&umhelper_sem);
 463 }
 464
 465 /**
 466  * __usermodehelper_disable - Prevent new helpers from being started.
 467  * @depth: New value to assign to usermodehelper_disabled.
 468  *
 469  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
 470  */
 471 int __usermodehelper_disable(enum umh_disable_depth depth)
 472 {
 473         long retval;
 474
 475         if (!depth)
 476                 return -EINVAL;
 477
 478         down_write(&umhelper_sem);
 479         usermodehelper_disabled = depth;
 480         up_write(&umhelper_sem);
 481
 482         /*
 483          * From now on call_usermodehelper_exec() won't start any new
 484          * helpers, so it is sufficient if running_helpers turns out to
 485          * be zero at one point (it may be increased later, but that
 486          * doesn't matter).
 487          */
 488         retval = wait_event_timeout(running_helpers_waitq,
 489                                         atomic_read(&running_helpers) == 0,
 490                                         RUNNING_HELPERS_TIMEOUT);
 491         if (retval)
 492                 return 0;
 493
 494         __usermodehelper_set_disable_depth(UMH_ENABLED);
 495         return -EAGAIN;
 496 }
 497
 498 static void helper_lock(void)
 499 {
 500         atomic_inc(&running_helpers);
 501         smp_mb__after_atomic_inc();
 502 }
 503
 504 static void helper_unlock(void)
 505 {
 506         if (atomic_dec_and_test(&running_helpers))
 507                 wake_up(&running_helpers_waitq);
 508 }
 509
 510 /**
 511  * call_usermodehelper_setup - prepare to call a usermode helper
 512  * @path: path to usermode executable
 513  * @argv: arg vector for process
 514  * @envp: environment for process
 515  * @gfp_mask: gfp mask for memory allocation
 516  * @cleanup: a cleanup function
 517  * @init: an init function
 518  * @data: arbitrary context sensitive data
 519  *
 520  * Returns either %NULL on allocation failure, or a subprocess_info
 521  * structure.  This should be passed to call_usermodehelper_exec to
 522  * exec the process and free the structure.
 523  *
 524  * The init function is used to customize the helper process prior to
 525  * exec.  A non-zero return code causes the process to error out, exit,
 526  * and return the failure to the calling process
 527  *
 528  * The cleanup function is just before ethe subprocess_info is about to
 529  * be freed.  This can be used for freeing the argv and envp.  The
 530  * Function must be runnable in either a process context or the
 531  * context in which call_usermodehelper_exec is called.
 532  */
 533 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
 534                 char **envp, gfp_t gfp_mask,
 535                 int (*init)(struct subprocess_info *info, struct cred *new),
 536                 void (*cleanup)(struct subprocess_info *info),
 537                 void *data)
 538 {
 539         struct subprocess_info *sub_info;
 540         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
 541         if (!sub_info)
 542                 goto out;
 543
 544         INIT_WORK(&sub_info->work, __call_usermodehelper);
 545         sub_info->path = path;
 546         sub_info->argv = argv;
 547         sub_info->envp = envp;
 548
 549         sub_info->cleanup = cleanup;
 550         sub_info->init = init;
 551         sub_info->data = data;
 552   out:
 553         return sub_info;
 554 }
 555 EXPORT_SYMBOL(call_usermodehelper_setup);
 556
 557 /**
 558  * call_usermodehelper_exec - start a usermode application
 559  * @sub_info: information about the subprocessa
 560  * @wait: wait for the application to finish and return status.
 561  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 562  *        when the program couldn't be exec'ed. This makes it safe to call
 563  *        from interrupt context.
 564  *
 565  * Runs a user-space application.  The application is started
 566  * asynchronously if wait is not set, and runs as a child of keventd.
 567  * (ie. it runs with full root capabilities).
 568  */
 569 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 570 {
 571         DECLARE_COMPLETION_ONSTACK(done);
 572         int retval = 0;
 573
 574         if (!sub_info->path) {
 575                 call_usermodehelper_freeinfo(sub_info);
 576                 return -EINVAL;
 577         }
 578         helper_lock();
 579         if (!khelper_wq || usermodehelper_disabled) {
 580                 retval = -EBUSY;
 581                 goto out;
 582         }
 583         /*
 584          * Worker thread must not wait for khelper thread at below
 585          * wait_for_completion() if the thread was created with CLONE_VFORK
 586          * flag, for khelper thread is already waiting for the thread at
 587          * wait_for_completion() in do_fork().
 588          */
 589         if (wait != UMH_NO_WAIT && current == kmod_thread_locker) {
 590                 retval = -EBUSY;
 591                 goto out;
 592         }
 593
 594         sub_info->complete = &done;
 595         sub_info->wait = wait;
 596
 597         queue_work(khelper_wq, &sub_info->work);
 598         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 599                 goto unlock;
 600
 601         if (wait & UMH_KILLABLE) {
 602                 retval = wait_for_completion_killable(&done);
 603                 if (!retval)
 604                         goto wait_done;
 605
 606                 /* umh_complete() will see NULL and free sub_info */
 607                 if (xchg(&sub_info->complete, NULL))
 608                         goto unlock;
 609                 /* fallthrough, umh_complete() was already called */
 610         }
 611
 612         wait_for_completion(&done);
 613 wait_done:
 614         retval = sub_info->retval;
 615 out:
 616         call_usermodehelper_freeinfo(sub_info);
 617 unlock:
 618         helper_unlock();
 619         return retval;
 620 }
 621 EXPORT_SYMBOL(call_usermodehelper_exec);
 622
 623 /**
 624  * call_usermodehelper() - prepare and start a usermode application
 625  * @path: path to usermode executable
 626  * @argv: arg vector for process
 627  * @envp: environment for process
 628  * @wait: wait for the application to finish and return status.
 629  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 630  *        when the program couldn't be exec'ed. This makes it safe to call
 631  *        from interrupt context.
 632  *
 633  * This function is the equivalent to use call_usermodehelper_setup() and
 634  * call_usermodehelper_exec().
 635  */
 636 int call_usermodehelper(char *path, char **argv, char **envp, int wait)
 637 {
 638         struct subprocess_info *info;
 639         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 640
 641         info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
 642                                          NULL, NULL, NULL);
 643         if (info == NULL)
 644                 return -ENOMEM;
 645
 646         return call_usermodehelper_exec(info, wait);
 647 }
 648 EXPORT_SYMBOL(call_usermodehelper);
 649
 650 static int proc_cap_handler(struct ctl_table *table, int write,
 651                          void __user *buffer, size_t *lenp, loff_t *ppos)
 652 {
 653         struct ctl_table t;
 654         unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
 655         kernel_cap_t new_cap;
 656         int err, i;
 657
 658         if (write && (!capable(CAP_SETPCAP) ||
 659                       !capable(CAP_SYS_MODULE)))
 660                 return -EPERM;
 661
 662         /*
 663          * convert from the global kernel_cap_t to the ulong array to print to
 664          * userspace if this is a read.
 665          */
 666         spin_lock(&umh_sysctl_lock);
 667         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
 668                 if (table->data == CAP_BSET)
 669                         cap_array[i] = usermodehelper_bset.cap[i];
 670                 else if (table->data == CAP_PI)
 671                         cap_array[i] = usermodehelper_inheritable.cap[i];
 672                 else
 673                         BUG();
 674         }
 675         spin_unlock(&umh_sysctl_lock);
 676
 677         t = *table;
 678         t.data = &cap_array;
 679
 680         /*
 681          * actually read or write and array of ulongs from userspace.  Remember
 682          * these are least significant 32 bits first
 683          */
 684         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
 685         if (err < 0)
 686                 return err;
 687
 688         /*
 689          * convert from the sysctl array of ulongs to the kernel_cap_t
 690          * internal representation
 691          */
 692         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
 693                 new_cap.cap[i] = cap_array[i];
 694
 695         /*
 696          * Drop everything not in the new_cap (but don't add things)
 697          */
 698         spin_lock(&umh_sysctl_lock);
 699         if (write) {
 700                 if (table->data == CAP_BSET)
 701                         usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 702                 if (table->data == CAP_PI)
 703                         usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
 704         }
 705         spin_unlock(&umh_sysctl_lock);
 706
 707         return 0;
 708 }
 709
 710 struct ctl_table usermodehelper_table[] = {
 711         {
 712                 .procname       = "bset",
 713                 .data           = CAP_BSET,
 714                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 715                 .mode           = 0600,
 716                 .proc_handler   = proc_cap_handler,
 717         },
 718         {
 719                 .procname       = "inheritable",
 720                 .data           = CAP_PI,
 721                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 722                 .mode           = 0600,
 723                 .proc_handler   = proc_cap_handler,
 724         },
 725         { }
 726 };
 727
 728 void __init usermodehelper_init(void)
 729 {
 730         khelper_wq = create_singlethread_workqueue("khelper");
 731         BUG_ON(!khelper_wq);
 732 }