kernel/umh.c

   1 /*
   2  * umh - the kernel usermode helper
   3  */
   4 #include <linux/module.h>
   5 #include <linux/sched.h>
   6 #include <linux/sched/task.h>
   7 #include <linux/binfmts.h>
   8 #include <linux/syscalls.h>
   9 #include <linux/unistd.h>
  10 #include <linux/kmod.h>
  11 #include <linux/slab.h>
  12 #include <linux/completion.h>
  13 #include <linux/cred.h>
  14 #include <linux/file.h>
  15 #include <linux/fdtable.h>
  16 #include <linux/fs_struct.h>
  17 #include <linux/workqueue.h>
  18 #include <linux/security.h>
  19 #include <linux/mount.h>
  20 #include <linux/kernel.h>
  21 #include <linux/init.h>
  22 #include <linux/resource.h>
  23 #include <linux/notifier.h>
  24 #include <linux/suspend.h>
  25 #include <linux/rwsem.h>
  26 #include <linux/ptrace.h>
  27 #include <linux/async.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/shmem_fs.h>
  30 #include <linux/pipe_fs_i.h>
  31
  32 #include <trace/events/module.h>
  33
  34 #define CAP_BSET        (void *)1
  35 #define CAP_PI          (void *)2
  36
  37 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
  38 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
  39 static DEFINE_SPINLOCK(umh_sysctl_lock);
  40 static DECLARE_RWSEM(umhelper_sem);
  41
  42 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
  43 {
  44         if (info->cleanup)
  45                 (*info->cleanup)(info);
  46         kfree(info);
  47 }
  48
  49 static void umh_complete(struct subprocess_info *sub_info)
  50 {
  51         struct completion *comp = xchg(&sub_info->complete, NULL);
  52         /*
  53          * See call_usermodehelper_exec(). If xchg() returns NULL
  54          * we own sub_info, the UMH_KILLABLE caller has gone away
  55          * or the caller used UMH_NO_WAIT.
  56          */
  57         if (comp)
  58                 complete(comp);
  59         else
  60                 call_usermodehelper_freeinfo(sub_info);
  61 }
  62
  63 /*
  64  * This is the task which runs the usermode application
  65  */
  66 static int call_usermodehelper_exec_async(void *data)
  67 {
  68         struct subprocess_info *sub_info = data;
  69         struct cred *new;
  70         int retval;
  71
  72         spin_lock_irq(&current->sighand->siglock);
  73         flush_signal_handlers(current, 1);
  74         spin_unlock_irq(&current->sighand->siglock);
  75
  76         /*
  77          * Initial kernel threads share ther FS with init, in order to
  78          * get the init root directory. But we've now created a new
  79          * thread that is going to execve a user process and has its own
  80          * 'struct fs_struct'. Reset umask to the default.
  81          */
  82         current->fs->umask = 0022;
  83
  84         /*
  85          * Our parent (unbound workqueue) runs with elevated scheduling
  86          * priority. Avoid propagating that into the userspace child.
  87          */
  88         set_user_nice(current, 0);
  89
  90         retval = -ENOMEM;
  91         new = prepare_kernel_cred(current);
  92         if (!new)
  93                 goto out;
  94
  95         spin_lock(&umh_sysctl_lock);
  96         new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
  97         new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
  98                                              new->cap_inheritable);
  99         spin_unlock(&umh_sysctl_lock);
 100
 101         if (sub_info->init) {
 102                 retval = sub_info->init(sub_info, new);
 103                 if (retval) {
 104                         abort_creds(new);
 105                         goto out;
 106                 }
 107         }
 108
 109         commit_creds(new);
 110
 111         sub_info->pid = task_pid_nr(current);
 112         if (sub_info->file)
 113                 retval = do_execve_file(sub_info->file,
 114                                         sub_info->argv, sub_info->envp);
 115         else
 116                 retval = do_execve(getname_kernel(sub_info->path),
 117                                    (const char __user *const __user *)sub_info->argv,
 118                                    (const char __user *const __user *)sub_info->envp);
 119 out:
 120         sub_info->retval = retval;
 121         /*
 122          * call_usermodehelper_exec_sync() will call umh_complete
 123          * if UHM_WAIT_PROC.
 124          */
 125         if (!(sub_info->wait & UMH_WAIT_PROC))
 126                 umh_complete(sub_info);
 127         if (!retval)
 128                 return 0;
 129         do_exit(0);
 130 }
 131
 132 /* Handles UMH_WAIT_PROC.  */
 133 static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
 134 {
 135         pid_t pid;
 136
 137         /* If SIGCLD is ignored kernel_wait4 won't populate the status. */
 138         kernel_sigaction(SIGCHLD, SIG_DFL);
 139         pid = kernel_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
 140         if (pid < 0) {
 141                 sub_info->retval = pid;
 142         } else {
 143                 int ret = -ECHILD;
 144                 /*
 145                  * Normally it is bogus to call wait4() from in-kernel because
 146                  * wait4() wants to write the exit code to a userspace address.
 147                  * But call_usermodehelper_exec_sync() always runs as kernel
 148                  * thread (workqueue) and put_user() to a kernel address works
 149                  * OK for kernel threads, due to their having an mm_segment_t
 150                  * which spans the entire address space.
 151                  *
 152                  * Thus the __user pointer cast is valid here.
 153                  */
 154                 kernel_wait4(pid, (int __user *)&ret, 0, NULL);
 155
 156                 /*
 157                  * If ret is 0, either call_usermodehelper_exec_async failed and
 158                  * the real error code is already in sub_info->retval or
 159                  * sub_info->retval is 0 anyway, so don't mess with it then.
 160                  */
 161                 if (ret)
 162                         sub_info->retval = ret;
 163         }
 164
 165         /* Restore default kernel sig handler */
 166         kernel_sigaction(SIGCHLD, SIG_IGN);
 167
 168         umh_complete(sub_info);
 169 }
 170
 171 /*
 172  * We need to create the usermodehelper kernel thread from a task that is affine
 173  * to an optimized set of CPUs (or nohz housekeeping ones) such that they
 174  * inherit a widest affinity irrespective of call_usermodehelper() callers with
 175  * possibly reduced affinity (eg: per-cpu workqueues). We don't want
 176  * usermodehelper targets to contend a busy CPU.
 177  *
 178  * Unbound workqueues provide such wide affinity and allow to block on
 179  * UMH_WAIT_PROC requests without blocking pending request (up to some limit).
 180  *
 181  * Besides, workqueues provide the privilege level that caller might not have
 182  * to perform the usermodehelper request.
 183  *
 184  */
 185 static void call_usermodehelper_exec_work(struct work_struct *work)
 186 {
 187         struct subprocess_info *sub_info =
 188                 container_of(work, struct subprocess_info, work);
 189
 190         if (sub_info->wait & UMH_WAIT_PROC) {
 191                 call_usermodehelper_exec_sync(sub_info);
 192         } else {
 193                 pid_t pid;
 194                 /*
 195                  * Use CLONE_PARENT to reparent it to kthreadd; we do not
 196                  * want to pollute current->children, and we need a parent
 197                  * that always ignores SIGCHLD to ensure auto-reaping.
 198                  */
 199                 pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
 200                                     CLONE_PARENT | SIGCHLD);
 201                 if (pid < 0) {
 202                         sub_info->retval = pid;
 203                         umh_complete(sub_info);
 204                 }
 205         }
 206 }
 207
 208 /*
 209  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
 210  * (used for preventing user land processes from being created after the user
 211  * land has been frozen during a system-wide hibernation or suspend operation).
 212  * Should always be manipulated under umhelper_sem acquired for write.
 213  */
 214 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 215
 216 /* Number of helpers running */
 217 static atomic_t running_helpers = ATOMIC_INIT(0);
 218
 219 /*
 220  * Wait queue head used by usermodehelper_disable() to wait for all running
 221  * helpers to finish.
 222  */
 223 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
 224
 225 /*
 226  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
 227  * to become 'false'.
 228  */
 229 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 230
 231 /*
 232  * Time to wait for running_helpers to become zero before the setting of
 233  * usermodehelper_disabled in usermodehelper_disable() fails
 234  */
 235 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
 236
 237 int usermodehelper_read_trylock(void)
 238 {
 239         DEFINE_WAIT(wait);
 240         int ret = 0;
 241
 242         down_read(&umhelper_sem);
 243         for (;;) {
 244                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 245                                 TASK_INTERRUPTIBLE);
 246                 if (!usermodehelper_disabled)
 247                         break;
 248
 249                 if (usermodehelper_disabled == UMH_DISABLED)
 250                         ret = -EAGAIN;
 251
 252                 up_read(&umhelper_sem);
 253
 254                 if (ret)
 255                         break;
 256
 257                 schedule();
 258                 try_to_freeze();
 259
 260                 down_read(&umhelper_sem);
 261         }
 262         finish_wait(&usermodehelper_disabled_waitq, &wait);
 263         return ret;
 264 }
 265 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
 266
 267 long usermodehelper_read_lock_wait(long timeout)
 268 {
 269         DEFINE_WAIT(wait);
 270
 271         if (timeout < 0)
 272                 return -EINVAL;
 273
 274         down_read(&umhelper_sem);
 275         for (;;) {
 276                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 277                                 TASK_UNINTERRUPTIBLE);
 278                 if (!usermodehelper_disabled)
 279                         break;
 280
 281                 up_read(&umhelper_sem);
 282
 283                 timeout = schedule_timeout(timeout);
 284                 if (!timeout)
 285                         break;
 286
 287                 down_read(&umhelper_sem);
 288         }
 289         finish_wait(&usermodehelper_disabled_waitq, &wait);
 290         return timeout;
 291 }
 292 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
 293
 294 void usermodehelper_read_unlock(void)
 295 {
 296         up_read(&umhelper_sem);
 297 }
 298 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 299
 300 /**
 301  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
 302  * @depth: New value to assign to usermodehelper_disabled.
 303  *
 304  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
 305  * writing) and wakeup tasks waiting for it to change.
 306  */
 307 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 308 {
 309         down_write(&umhelper_sem);
 310         usermodehelper_disabled = depth;
 311         wake_up(&usermodehelper_disabled_waitq);
 312         up_write(&umhelper_sem);
 313 }
 314
 315 /**
 316  * __usermodehelper_disable - Prevent new helpers from being started.
 317  * @depth: New value to assign to usermodehelper_disabled.
 318  *
 319  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
 320  */
 321 int __usermodehelper_disable(enum umh_disable_depth depth)
 322 {
 323         long retval;
 324
 325         if (!depth)
 326                 return -EINVAL;
 327
 328         down_write(&umhelper_sem);
 329         usermodehelper_disabled = depth;
 330         up_write(&umhelper_sem);
 331
 332         /*
 333          * From now on call_usermodehelper_exec() won't start any new
 334          * helpers, so it is sufficient if running_helpers turns out to
 335          * be zero at one point (it may be increased later, but that
 336          * doesn't matter).
 337          */
 338         retval = wait_event_timeout(running_helpers_waitq,
 339                                         atomic_read(&running_helpers) == 0,
 340                                         RUNNING_HELPERS_TIMEOUT);
 341         if (retval)
 342                 return 0;
 343
 344         __usermodehelper_set_disable_depth(UMH_ENABLED);
 345         return -EAGAIN;
 346 }
 347
 348 static void helper_lock(void)
 349 {
 350         atomic_inc(&running_helpers);
 351         smp_mb__after_atomic();
 352 }
 353
 354 static void helper_unlock(void)
 355 {
 356         if (atomic_dec_and_test(&running_helpers))
 357                 wake_up(&running_helpers_waitq);
 358 }
 359
 360 /**
 361  * call_usermodehelper_setup - prepare to call a usermode helper
 362  * @path: path to usermode executable
 363  * @argv: arg vector for process
 364  * @envp: environment for process
 365  * @gfp_mask: gfp mask for memory allocation
 366  * @cleanup: a cleanup function
 367  * @init: an init function
 368  * @data: arbitrary context sensitive data
 369  *
 370  * Returns either %NULL on allocation failure, or a subprocess_info
 371  * structure.  This should be passed to call_usermodehelper_exec to
 372  * exec the process and free the structure.
 373  *
 374  * The init function is used to customize the helper process prior to
 375  * exec.  A non-zero return code causes the process to error out, exit,
 376  * and return the failure to the calling process
 377  *
 378  * The cleanup function is just before ethe subprocess_info is about to
 379  * be freed.  This can be used for freeing the argv and envp.  The
 380  * Function must be runnable in either a process context or the
 381  * context in which call_usermodehelper_exec is called.
 382  */
 383 struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
 384                 char **envp, gfp_t gfp_mask,
 385                 int (*init)(struct subprocess_info *info, struct cred *new),
 386                 void (*cleanup)(struct subprocess_info *info),
 387                 void *data)
 388 {
 389         struct subprocess_info *sub_info;
 390         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
 391         if (!sub_info)
 392                 goto out;
 393
 394         INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
 395
 396 #ifdef CONFIG_STATIC_USERMODEHELPER
 397         sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
 398 #else
 399         sub_info->path = path;
 400 #endif
 401         sub_info->argv = argv;
 402         sub_info->envp = envp;
 403
 404         sub_info->cleanup = cleanup;
 405         sub_info->init = init;
 406         sub_info->data = data;
 407   out:
 408         return sub_info;
 409 }
 410 EXPORT_SYMBOL(call_usermodehelper_setup);
 411
 412 struct subprocess_info *call_usermodehelper_setup_file(struct file *file,
 413                 int (*init)(struct subprocess_info *info, struct cred *new),
 414                 void (*cleanup)(struct subprocess_info *info), void *data)
 415 {
 416         struct subprocess_info *sub_info;
 417
 418         sub_info = kzalloc(sizeof(struct subprocess_info), GFP_KERNEL);
 419         if (!sub_info)
 420                 return NULL;
 421
 422         INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
 423         sub_info->path = "none";
 424         sub_info->file = file;
 425         sub_info->init = init;
 426         sub_info->cleanup = cleanup;
 427         sub_info->data = data;
 428         return sub_info;
 429 }
 430
 431 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 432 {
 433         struct umh_info *umh_info = info->data;
 434         struct file *from_umh[2];
 435         struct file *to_umh[2];
 436         int err;
 437
 438         /* create pipe to send data to umh */
 439         err = create_pipe_files(to_umh, 0);
 440         if (err)
 441                 return err;
 442         err = replace_fd(0, to_umh[0], 0);
 443         fput(to_umh[0]);
 444         if (err < 0) {
 445                 fput(to_umh[1]);
 446                 return err;
 447         }
 448
 449         /* create pipe to receive data from umh */
 450         err = create_pipe_files(from_umh, 0);
 451         if (err) {
 452                 fput(to_umh[1]);
 453                 replace_fd(0, NULL, 0);
 454                 return err;
 455         }
 456         err = replace_fd(1, from_umh[1], 0);
 457         fput(from_umh[1]);
 458         if (err < 0) {
 459                 fput(to_umh[1]);
 460                 replace_fd(0, NULL, 0);
 461                 fput(from_umh[0]);
 462                 return err;
 463         }
 464
 465         umh_info->pipe_to_umh = to_umh[1];
 466         umh_info->pipe_from_umh = from_umh[0];
 467         return 0;
 468 }
 469
 470 static void umh_save_pid(struct subprocess_info *info)
 471 {
 472         struct umh_info *umh_info = info->data;
 473
 474         umh_info->pid = info->pid;
 475 }
 476
 477 /**
 478  * fork_usermode_blob - fork a blob of bytes as a usermode process
 479  * @data: a blob of bytes that can be do_execv-ed as a file
 480  * @len: length of the blob
 481  * @info: information about usermode process (shouldn't be NULL)
 482  *
 483  * Returns either negative error or zero which indicates success
 484  * in executing a blob of bytes as a usermode process. In such
 485  * case 'struct umh_info *info' is populated with two pipes
 486  * and a pid of the process. The caller is responsible for health
 487  * check of the user process, killing it via pid, and closing the
 488  * pipes when user process is no longer needed.
 489  */
 490 int fork_usermode_blob(void *data, size_t len, struct umh_info *info)
 491 {
 492         struct subprocess_info *sub_info;
 493         struct file *file;
 494         ssize_t written;
 495         loff_t pos = 0;
 496         int err;
 497
 498         file = shmem_kernel_file_setup("", len, 0);
 499         if (IS_ERR(file))
 500                 return PTR_ERR(file);
 501
 502         written = kernel_write(file, data, len, &pos);
 503         if (written != len) {
 504                 err = written;
 505                 if (err >= 0)
 506                         err = -ENOMEM;
 507                 goto out;
 508         }
 509
 510         err = -ENOMEM;
 511         sub_info = call_usermodehelper_setup_file(file, umh_pipe_setup,
 512                                                   umh_save_pid, info);
 513         if (!sub_info)
 514                 goto out;
 515
 516         err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
 517 out:
 518         fput(file);
 519         return err;
 520 }
 521 EXPORT_SYMBOL_GPL(fork_usermode_blob);
 522
 523 /**
 524  * call_usermodehelper_exec - start a usermode application
 525  * @sub_info: information about the subprocessa
 526  * @wait: wait for the application to finish and return status.
 527  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 528  *        when the program couldn't be exec'ed. This makes it safe to call
 529  *        from interrupt context.
 530  *
 531  * Runs a user-space application.  The application is started
 532  * asynchronously if wait is not set, and runs as a child of system workqueues.
 533  * (ie. it runs with full root capabilities and optimized affinity).
 534  *
 535  * Note: successful return value does not guarantee the helper was called at
 536  * all. You can't rely on sub_info->{init,cleanup} being called even for
 537  * UMH_WAIT_* wait modes as STATIC_USERMODEHELPER_PATH="" turns all helpers
 538  * into a successful no-op.
 539  */
 540 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 541 {
 542         DECLARE_COMPLETION_ONSTACK(done);
 543         int retval = 0;
 544
 545         if (!sub_info->path) {
 546                 call_usermodehelper_freeinfo(sub_info);
 547                 return -EINVAL;
 548         }
 549         helper_lock();
 550         if (usermodehelper_disabled) {
 551                 retval = -EBUSY;
 552                 goto out;
 553         }
 554
 555         /*
 556          * If there is no binary for us to call, then just return and get out of
 557          * here.  This allows us to set STATIC_USERMODEHELPER_PATH to "" and
 558          * disable all call_usermodehelper() calls.
 559          */
 560         if (strlen(sub_info->path) == 0)
 561                 goto out;
 562
 563         /*
 564          * Set the completion pointer only if there is a waiter.
 565          * This makes it possible to use umh_complete to free
 566          * the data structure in case of UMH_NO_WAIT.
 567          */
 568         sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
 569         sub_info->wait = wait;
 570
 571         queue_work(system_unbound_wq, &sub_info->work);
 572         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 573                 goto unlock;
 574
 575         if (wait & UMH_KILLABLE) {
 576                 retval = wait_for_completion_killable(&done);
 577                 if (!retval)
 578                         goto wait_done;
 579
 580                 /* umh_complete() will see NULL and free sub_info */
 581                 if (xchg(&sub_info->complete, NULL))
 582                         goto unlock;
 583                 /* fallthrough, umh_complete() was already called */
 584         }
 585
 586         wait_for_completion(&done);
 587 wait_done:
 588         retval = sub_info->retval;
 589 out:
 590         call_usermodehelper_freeinfo(sub_info);
 591 unlock:
 592         helper_unlock();
 593         return retval;
 594 }
 595 EXPORT_SYMBOL(call_usermodehelper_exec);
 596
 597 /**
 598  * call_usermodehelper() - prepare and start a usermode application
 599  * @path: path to usermode executable
 600  * @argv: arg vector for process
 601  * @envp: environment for process
 602  * @wait: wait for the application to finish and return status.
 603  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 604  *        when the program couldn't be exec'ed. This makes it safe to call
 605  *        from interrupt context.
 606  *
 607  * This function is the equivalent to use call_usermodehelper_setup() and
 608  * call_usermodehelper_exec().
 609  */
 610 int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
 611 {
 612         struct subprocess_info *info;
 613         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 614
 615         info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
 616                                          NULL, NULL, NULL);
 617         if (info == NULL)
 618                 return -ENOMEM;
 619
 620         return call_usermodehelper_exec(info, wait);
 621 }
 622 EXPORT_SYMBOL(call_usermodehelper);
 623
 624 static int proc_cap_handler(struct ctl_table *table, int write,
 625                          void __user *buffer, size_t *lenp, loff_t *ppos)
 626 {
 627         struct ctl_table t;
 628         unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
 629         kernel_cap_t new_cap;
 630         int err, i;
 631
 632         if (write && (!capable(CAP_SETPCAP) ||
 633                       !capable(CAP_SYS_MODULE)))
 634                 return -EPERM;
 635
 636         /*
 637          * convert from the global kernel_cap_t to the ulong array to print to
 638          * userspace if this is a read.
 639          */
 640         spin_lock(&umh_sysctl_lock);
 641         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
 642                 if (table->data == CAP_BSET)
 643                         cap_array[i] = usermodehelper_bset.cap[i];
 644                 else if (table->data == CAP_PI)
 645                         cap_array[i] = usermodehelper_inheritable.cap[i];
 646                 else
 647                         BUG();
 648         }
 649         spin_unlock(&umh_sysctl_lock);
 650
 651         t = *table;
 652         t.data = &cap_array;
 653
 654         /*
 655          * actually read or write and array of ulongs from userspace.  Remember
 656          * these are least significant 32 bits first
 657          */
 658         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
 659         if (err < 0)
 660                 return err;
 661
 662         /*
 663          * convert from the sysctl array of ulongs to the kernel_cap_t
 664          * internal representation
 665          */
 666         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
 667                 new_cap.cap[i] = cap_array[i];
 668
 669         /*
 670          * Drop everything not in the new_cap (but don't add things)
 671          */
 672         if (write) {
 673                 spin_lock(&umh_sysctl_lock);
 674                 if (table->data == CAP_BSET)
 675                         usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 676                 if (table->data == CAP_PI)
 677                         usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
 678                 spin_unlock(&umh_sysctl_lock);
 679         }
 680
 681         return 0;
 682 }
 683
 684 struct ctl_table usermodehelper_table[] = {
 685         {
 686                 .procname       = "bset",
 687                 .data           = CAP_BSET,
 688                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 689                 .mode           = 0600,
 690                 .proc_handler   = proc_cap_handler,
 691         },
 692         {
 693                 .procname       = "inheritable",
 694                 .data           = CAP_PI,
 695                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 696                 .mode           = 0600,
 697                 .proc_handler   = proc_cap_handler,
 698         },
 699         { }
 700 };