kernel/umh.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * umh - the kernel usermode helper
   4  */
   5 #include <linux/module.h>
   6 #include <linux/sched.h>
   7 #include <linux/sched/task.h>
   8 #include <linux/binfmts.h>
   9 #include <linux/syscalls.h>
  10 #include <linux/unistd.h>
  11 #include <linux/kmod.h>
  12 #include <linux/slab.h>
  13 #include <linux/completion.h>
  14 #include <linux/cred.h>
  15 #include <linux/file.h>
  16 #include <linux/fdtable.h>
  17 #include <linux/fs_struct.h>
  18 #include <linux/workqueue.h>
  19 #include <linux/security.h>
  20 #include <linux/mount.h>
  21 #include <linux/kernel.h>
  22 #include <linux/init.h>
  23 #include <linux/resource.h>
  24 #include <linux/notifier.h>
  25 #include <linux/suspend.h>
  26 #include <linux/rwsem.h>
  27 #include <linux/ptrace.h>
  28 #include <linux/async.h>
  29 #include <linux/uaccess.h>
  30 #include <linux/shmem_fs.h>
  31 #include <linux/pipe_fs_i.h>
  32
  33 #include <trace/events/module.h>
  34
  35 #define CAP_BSET        (void *)1
  36 #define CAP_PI          (void *)2
  37
  38 static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
  39 static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
  40 static DEFINE_SPINLOCK(umh_sysctl_lock);
  41 static DECLARE_RWSEM(umhelper_sem);
  42 static LIST_HEAD(umh_list);
  43 static DEFINE_MUTEX(umh_list_lock);
  44
  45 static void call_usermodehelper_freeinfo(struct subprocess_info *info)
  46 {
  47         if (info->cleanup)
  48                 (*info->cleanup)(info);
  49         kfree(info);
  50 }
  51
  52 static void umh_complete(struct subprocess_info *sub_info)
  53 {
  54         struct completion *comp = xchg(&sub_info->complete, NULL);
  55         /*
  56          * See call_usermodehelper_exec(). If xchg() returns NULL
  57          * we own sub_info, the UMH_KILLABLE caller has gone away
  58          * or the caller used UMH_NO_WAIT.
  59          */
  60         if (comp)
  61                 complete(comp);
  62         else
  63                 call_usermodehelper_freeinfo(sub_info);
  64 }
  65
  66 /*
  67  * This is the task which runs the usermode application
  68  */
  69 static int call_usermodehelper_exec_async(void *data)
  70 {
  71         struct subprocess_info *sub_info = data;
  72         struct cred *new;
  73         int retval;
  74
  75         spin_lock_irq(&current->sighand->siglock);
  76         flush_signal_handlers(current, 1);
  77         spin_unlock_irq(&current->sighand->siglock);
  78
  79         /*
  80          * Initial kernel threads share ther FS with init, in order to
  81          * get the init root directory. But we've now created a new
  82          * thread that is going to execve a user process and has its own
  83          * 'struct fs_struct'. Reset umask to the default.
  84          */
  85         current->fs->umask = 0022;
  86
  87         /*
  88          * Our parent (unbound workqueue) runs with elevated scheduling
  89          * priority. Avoid propagating that into the userspace child.
  90          */
  91         set_user_nice(current, 0);
  92
  93         retval = -ENOMEM;
  94         new = prepare_kernel_cred(current);
  95         if (!new)
  96                 goto out;
  97
  98         spin_lock(&umh_sysctl_lock);
  99         new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
 100         new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
 101                                              new->cap_inheritable);
 102         spin_unlock(&umh_sysctl_lock);
 103
 104         if (sub_info->init) {
 105                 retval = sub_info->init(sub_info, new);
 106                 if (retval) {
 107                         abort_creds(new);
 108                         goto out;
 109                 }
 110         }
 111
 112         commit_creds(new);
 113
 114         sub_info->pid = task_pid_nr(current);
 115         if (sub_info->file) {
 116                 retval = do_execve_file(sub_info->file,
 117                                         sub_info->argv, sub_info->envp);
 118                 if (!retval)
 119                         current->flags |= PF_UMH;
 120         } else
 121                 retval = do_execve(getname_kernel(sub_info->path),
 122                                    (const char __user *const __user *)sub_info->argv,
 123                                    (const char __user *const __user *)sub_info->envp);
 124 out:
 125         sub_info->retval = retval;
 126         /*
 127          * call_usermodehelper_exec_sync() will call umh_complete
 128          * if UHM_WAIT_PROC.
 129          */
 130         if (!(sub_info->wait & UMH_WAIT_PROC))
 131                 umh_complete(sub_info);
 132         if (!retval)
 133                 return 0;
 134         do_exit(0);
 135 }
 136
 137 /* Handles UMH_WAIT_PROC.  */
 138 static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
 139 {
 140         pid_t pid;
 141
 142         /* If SIGCLD is ignored kernel_wait4 won't populate the status. */
 143         kernel_sigaction(SIGCHLD, SIG_DFL);
 144         pid = kernel_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
 145         if (pid < 0) {
 146                 sub_info->retval = pid;
 147         } else {
 148                 int ret = -ECHILD;
 149                 /*
 150                  * Normally it is bogus to call wait4() from in-kernel because
 151                  * wait4() wants to write the exit code to a userspace address.
 152                  * But call_usermodehelper_exec_sync() always runs as kernel
 153                  * thread (workqueue) and put_user() to a kernel address works
 154                  * OK for kernel threads, due to their having an mm_segment_t
 155                  * which spans the entire address space.
 156                  *
 157                  * Thus the __user pointer cast is valid here.
 158                  */
 159                 kernel_wait4(pid, (int __user *)&ret, 0, NULL);
 160
 161                 /*
 162                  * If ret is 0, either call_usermodehelper_exec_async failed and
 163                  * the real error code is already in sub_info->retval or
 164                  * sub_info->retval is 0 anyway, so don't mess with it then.
 165                  */
 166                 if (ret)
 167                         sub_info->retval = ret;
 168         }
 169
 170         /* Restore default kernel sig handler */
 171         kernel_sigaction(SIGCHLD, SIG_IGN);
 172
 173         umh_complete(sub_info);
 174 }
 175
 176 /*
 177  * We need to create the usermodehelper kernel thread from a task that is affine
 178  * to an optimized set of CPUs (or nohz housekeeping ones) such that they
 179  * inherit a widest affinity irrespective of call_usermodehelper() callers with
 180  * possibly reduced affinity (eg: per-cpu workqueues). We don't want
 181  * usermodehelper targets to contend a busy CPU.
 182  *
 183  * Unbound workqueues provide such wide affinity and allow to block on
 184  * UMH_WAIT_PROC requests without blocking pending request (up to some limit).
 185  *
 186  * Besides, workqueues provide the privilege level that caller might not have
 187  * to perform the usermodehelper request.
 188  *
 189  */
 190 static void call_usermodehelper_exec_work(struct work_struct *work)
 191 {
 192         struct subprocess_info *sub_info =
 193                 container_of(work, struct subprocess_info, work);
 194
 195         if (sub_info->wait & UMH_WAIT_PROC) {
 196                 call_usermodehelper_exec_sync(sub_info);
 197         } else {
 198                 pid_t pid;
 199                 /*
 200                  * Use CLONE_PARENT to reparent it to kthreadd; we do not
 201                  * want to pollute current->children, and we need a parent
 202                  * that always ignores SIGCHLD to ensure auto-reaping.
 203                  */
 204                 pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
 205                                     CLONE_PARENT | SIGCHLD);
 206                 if (pid < 0) {
 207                         sub_info->retval = pid;
 208                         umh_complete(sub_info);
 209                 }
 210         }
 211 }
 212
 213 /*
 214  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
 215  * (used for preventing user land processes from being created after the user
 216  * land has been frozen during a system-wide hibernation or suspend operation).
 217  * Should always be manipulated under umhelper_sem acquired for write.
 218  */
 219 static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED;
 220
 221 /* Number of helpers running */
 222 static atomic_t running_helpers = ATOMIC_INIT(0);
 223
 224 /*
 225  * Wait queue head used by usermodehelper_disable() to wait for all running
 226  * helpers to finish.
 227  */
 228 static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq);
 229
 230 /*
 231  * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled
 232  * to become 'false'.
 233  */
 234 static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq);
 235
 236 /*
 237  * Time to wait for running_helpers to become zero before the setting of
 238  * usermodehelper_disabled in usermodehelper_disable() fails
 239  */
 240 #define RUNNING_HELPERS_TIMEOUT (5 * HZ)
 241
 242 int usermodehelper_read_trylock(void)
 243 {
 244         DEFINE_WAIT(wait);
 245         int ret = 0;
 246
 247         down_read(&umhelper_sem);
 248         for (;;) {
 249                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 250                                 TASK_INTERRUPTIBLE);
 251                 if (!usermodehelper_disabled)
 252                         break;
 253
 254                 if (usermodehelper_disabled == UMH_DISABLED)
 255                         ret = -EAGAIN;
 256
 257                 up_read(&umhelper_sem);
 258
 259                 if (ret)
 260                         break;
 261
 262                 schedule();
 263                 try_to_freeze();
 264
 265                 down_read(&umhelper_sem);
 266         }
 267         finish_wait(&usermodehelper_disabled_waitq, &wait);
 268         return ret;
 269 }
 270 EXPORT_SYMBOL_GPL(usermodehelper_read_trylock);
 271
 272 long usermodehelper_read_lock_wait(long timeout)
 273 {
 274         DEFINE_WAIT(wait);
 275
 276         if (timeout < 0)
 277                 return -EINVAL;
 278
 279         down_read(&umhelper_sem);
 280         for (;;) {
 281                 prepare_to_wait(&usermodehelper_disabled_waitq, &wait,
 282                                 TASK_UNINTERRUPTIBLE);
 283                 if (!usermodehelper_disabled)
 284                         break;
 285
 286                 up_read(&umhelper_sem);
 287
 288                 timeout = schedule_timeout(timeout);
 289                 if (!timeout)
 290                         break;
 291
 292                 down_read(&umhelper_sem);
 293         }
 294         finish_wait(&usermodehelper_disabled_waitq, &wait);
 295         return timeout;
 296 }
 297 EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait);
 298
 299 void usermodehelper_read_unlock(void)
 300 {
 301         up_read(&umhelper_sem);
 302 }
 303 EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 304
 305 /**
 306  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
 307  * @depth: New value to assign to usermodehelper_disabled.
 308  *
 309  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
 310  * writing) and wakeup tasks waiting for it to change.
 311  */
 312 void __usermodehelper_set_disable_depth(enum umh_disable_depth depth)
 313 {
 314         down_write(&umhelper_sem);
 315         usermodehelper_disabled = depth;
 316         wake_up(&usermodehelper_disabled_waitq);
 317         up_write(&umhelper_sem);
 318 }
 319
 320 /**
 321  * __usermodehelper_disable - Prevent new helpers from being started.
 322  * @depth: New value to assign to usermodehelper_disabled.
 323  *
 324  * Set usermodehelper_disabled to @depth and wait for running helpers to exit.
 325  */
 326 int __usermodehelper_disable(enum umh_disable_depth depth)
 327 {
 328         long retval;
 329
 330         if (!depth)
 331                 return -EINVAL;
 332
 333         down_write(&umhelper_sem);
 334         usermodehelper_disabled = depth;
 335         up_write(&umhelper_sem);
 336
 337         /*
 338          * From now on call_usermodehelper_exec() won't start any new
 339          * helpers, so it is sufficient if running_helpers turns out to
 340          * be zero at one point (it may be increased later, but that
 341          * doesn't matter).
 342          */
 343         retval = wait_event_timeout(running_helpers_waitq,
 344                                         atomic_read(&running_helpers) == 0,
 345                                         RUNNING_HELPERS_TIMEOUT);
 346         if (retval)
 347                 return 0;
 348
 349         __usermodehelper_set_disable_depth(UMH_ENABLED);
 350         return -EAGAIN;
 351 }
 352
 353 static void helper_lock(void)
 354 {
 355         atomic_inc(&running_helpers);
 356         smp_mb__after_atomic();
 357 }
 358
 359 static void helper_unlock(void)
 360 {
 361         if (atomic_dec_and_test(&running_helpers))
 362                 wake_up(&running_helpers_waitq);
 363 }
 364
 365 /**
 366  * call_usermodehelper_setup - prepare to call a usermode helper
 367  * @path: path to usermode executable
 368  * @argv: arg vector for process
 369  * @envp: environment for process
 370  * @gfp_mask: gfp mask for memory allocation
 371  * @cleanup: a cleanup function
 372  * @init: an init function
 373  * @data: arbitrary context sensitive data
 374  *
 375  * Returns either %NULL on allocation failure, or a subprocess_info
 376  * structure.  This should be passed to call_usermodehelper_exec to
 377  * exec the process and free the structure.
 378  *
 379  * The init function is used to customize the helper process prior to
 380  * exec.  A non-zero return code causes the process to error out, exit,
 381  * and return the failure to the calling process
 382  *
 383  * The cleanup function is just before ethe subprocess_info is about to
 384  * be freed.  This can be used for freeing the argv and envp.  The
 385  * Function must be runnable in either a process context or the
 386  * context in which call_usermodehelper_exec is called.
 387  */
 388 struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
 389                 char **envp, gfp_t gfp_mask,
 390                 int (*init)(struct subprocess_info *info, struct cred *new),
 391                 void (*cleanup)(struct subprocess_info *info),
 392                 void *data)
 393 {
 394         struct subprocess_info *sub_info;
 395         sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask);
 396         if (!sub_info)
 397                 goto out;
 398
 399         INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
 400
 401 #ifdef CONFIG_STATIC_USERMODEHELPER
 402         sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
 403 #else
 404         sub_info->path = path;
 405 #endif
 406         sub_info->argv = argv;
 407         sub_info->envp = envp;
 408
 409         sub_info->cleanup = cleanup;
 410         sub_info->init = init;
 411         sub_info->data = data;
 412   out:
 413         return sub_info;
 414 }
 415 EXPORT_SYMBOL(call_usermodehelper_setup);
 416
 417 struct subprocess_info *call_usermodehelper_setup_file(struct file *file,
 418                 int (*init)(struct subprocess_info *info, struct cred *new),
 419                 void (*cleanup)(struct subprocess_info *info), void *data)
 420 {
 421         struct subprocess_info *sub_info;
 422         struct umh_info *info = data;
 423         const char *cmdline = (info->cmdline) ? info->cmdline : "usermodehelper";
 424
 425         sub_info = kzalloc(sizeof(struct subprocess_info), GFP_KERNEL);
 426         if (!sub_info)
 427                 return NULL;
 428
 429         sub_info->argv = argv_split(GFP_KERNEL, cmdline, NULL);
 430         if (!sub_info->argv) {
 431                 kfree(sub_info);
 432                 return NULL;
 433         }
 434
 435         INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
 436         sub_info->path = "none";
 437         sub_info->file = file;
 438         sub_info->init = init;
 439         sub_info->cleanup = cleanup;
 440         sub_info->data = data;
 441         return sub_info;
 442 }
 443
 444 static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 445 {
 446         struct umh_info *umh_info = info->data;
 447         struct file *from_umh[2];
 448         struct file *to_umh[2];
 449         int err;
 450
 451         /* create pipe to send data to umh */
 452         err = create_pipe_files(to_umh, 0);
 453         if (err)
 454                 return err;
 455         err = replace_fd(0, to_umh[0], 0);
 456         fput(to_umh[0]);
 457         if (err < 0) {
 458                 fput(to_umh[1]);
 459                 return err;
 460         }
 461
 462         /* create pipe to receive data from umh */
 463         err = create_pipe_files(from_umh, 0);
 464         if (err) {
 465                 fput(to_umh[1]);
 466                 replace_fd(0, NULL, 0);
 467                 return err;
 468         }
 469         err = replace_fd(1, from_umh[1], 0);
 470         fput(from_umh[1]);
 471         if (err < 0) {
 472                 fput(to_umh[1]);
 473                 replace_fd(0, NULL, 0);
 474                 fput(from_umh[0]);
 475                 return err;
 476         }
 477
 478         umh_info->pipe_to_umh = to_umh[1];
 479         umh_info->pipe_from_umh = from_umh[0];
 480         return 0;
 481 }
 482
 483 static void umh_clean_and_save_pid(struct subprocess_info *info)
 484 {
 485         struct umh_info *umh_info = info->data;
 486
 487         /* cleanup if umh_pipe_setup() was successful but exec failed */
 488         if (info->pid && info->retval) {
 489                 fput(umh_info->pipe_to_umh);
 490                 fput(umh_info->pipe_from_umh);
 491         }
 492
 493         argv_free(info->argv);
 494         umh_info->pid = info->pid;
 495 }
 496
 497 /**
 498  * fork_usermode_blob - fork a blob of bytes as a usermode process
 499  * @data: a blob of bytes that can be do_execv-ed as a file
 500  * @len: length of the blob
 501  * @info: information about usermode process (shouldn't be NULL)
 502  *
 503  * If info->cmdline is set it will be used as command line for the
 504  * user process, else "usermodehelper" is used.
 505  *
 506  * Returns either negative error or zero which indicates success
 507  * in executing a blob of bytes as a usermode process. In such
 508  * case 'struct umh_info *info' is populated with two pipes
 509  * and a pid of the process. The caller is responsible for health
 510  * check of the user process, killing it via pid, and closing the
 511  * pipes when user process is no longer needed.
 512  */
 513 int fork_usermode_blob(void *data, size_t len, struct umh_info *info)
 514 {
 515         struct subprocess_info *sub_info;
 516         struct file *file;
 517         ssize_t written;
 518         loff_t pos = 0;
 519         int err;
 520
 521         file = shmem_kernel_file_setup("", len, 0);
 522         if (IS_ERR(file))
 523                 return PTR_ERR(file);
 524
 525         written = kernel_write(file, data, len, &pos);
 526         if (written != len) {
 527                 err = written;
 528                 if (err >= 0)
 529                         err = -ENOMEM;
 530                 goto out;
 531         }
 532
 533         err = -ENOMEM;
 534         sub_info = call_usermodehelper_setup_file(file, umh_pipe_setup,
 535                                                   umh_clean_and_save_pid, info);
 536         if (!sub_info)
 537                 goto out;
 538
 539         err = call_usermodehelper_exec(sub_info, UMH_WAIT_EXEC);
 540         if (!err) {
 541                 mutex_lock(&umh_list_lock);
 542                 list_add(&info->list, &umh_list);
 543                 mutex_unlock(&umh_list_lock);
 544         }
 545 out:
 546         fput(file);
 547         return err;
 548 }
 549 EXPORT_SYMBOL_GPL(fork_usermode_blob);
 550
 551 /**
 552  * call_usermodehelper_exec - start a usermode application
 553  * @sub_info: information about the subprocessa
 554  * @wait: wait for the application to finish and return status.
 555  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 556  *        when the program couldn't be exec'ed. This makes it safe to call
 557  *        from interrupt context.
 558  *
 559  * Runs a user-space application.  The application is started
 560  * asynchronously if wait is not set, and runs as a child of system workqueues.
 561  * (ie. it runs with full root capabilities and optimized affinity).
 562  *
 563  * Note: successful return value does not guarantee the helper was called at
 564  * all. You can't rely on sub_info->{init,cleanup} being called even for
 565  * UMH_WAIT_* wait modes as STATIC_USERMODEHELPER_PATH="" turns all helpers
 566  * into a successful no-op.
 567  */
 568 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 569 {
 570         DECLARE_COMPLETION_ONSTACK(done);
 571         int retval = 0;
 572
 573         if (!sub_info->path) {
 574                 call_usermodehelper_freeinfo(sub_info);
 575                 return -EINVAL;
 576         }
 577         helper_lock();
 578         if (usermodehelper_disabled) {
 579                 retval = -EBUSY;
 580                 goto out;
 581         }
 582
 583         /*
 584          * If there is no binary for us to call, then just return and get out of
 585          * here.  This allows us to set STATIC_USERMODEHELPER_PATH to "" and
 586          * disable all call_usermodehelper() calls.
 587          */
 588         if (strlen(sub_info->path) == 0)
 589                 goto out;
 590
 591         /*
 592          * Set the completion pointer only if there is a waiter.
 593          * This makes it possible to use umh_complete to free
 594          * the data structure in case of UMH_NO_WAIT.
 595          */
 596         sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
 597         sub_info->wait = wait;
 598
 599         queue_work(system_unbound_wq, &sub_info->work);
 600         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
 601                 goto unlock;
 602
 603         if (wait & UMH_KILLABLE) {
 604                 retval = wait_for_completion_killable(&done);
 605                 if (!retval)
 606                         goto wait_done;
 607
 608                 /* umh_complete() will see NULL and free sub_info */
 609                 if (xchg(&sub_info->complete, NULL))
 610                         goto unlock;
 611                 /* fallthrough, umh_complete() was already called */
 612         }
 613
 614         wait_for_completion(&done);
 615 wait_done:
 616         retval = sub_info->retval;
 617 out:
 618         call_usermodehelper_freeinfo(sub_info);
 619 unlock:
 620         helper_unlock();
 621         return retval;
 622 }
 623 EXPORT_SYMBOL(call_usermodehelper_exec);
 624
 625 /**
 626  * call_usermodehelper() - prepare and start a usermode application
 627  * @path: path to usermode executable
 628  * @argv: arg vector for process
 629  * @envp: environment for process
 630  * @wait: wait for the application to finish and return status.
 631  *        when UMH_NO_WAIT don't wait at all, but you get no useful error back
 632  *        when the program couldn't be exec'ed. This makes it safe to call
 633  *        from interrupt context.
 634  *
 635  * This function is the equivalent to use call_usermodehelper_setup() and
 636  * call_usermodehelper_exec().
 637  */
 638 int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
 639 {
 640         struct subprocess_info *info;
 641         gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 642
 643         info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
 644                                          NULL, NULL, NULL);
 645         if (info == NULL)
 646                 return -ENOMEM;
 647
 648         return call_usermodehelper_exec(info, wait);
 649 }
 650 EXPORT_SYMBOL(call_usermodehelper);
 651
 652 static int proc_cap_handler(struct ctl_table *table, int write,
 653                          void __user *buffer, size_t *lenp, loff_t *ppos)
 654 {
 655         struct ctl_table t;
 656         unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
 657         kernel_cap_t new_cap;
 658         int err, i;
 659
 660         if (write && (!capable(CAP_SETPCAP) ||
 661                       !capable(CAP_SYS_MODULE)))
 662                 return -EPERM;
 663
 664         /*
 665          * convert from the global kernel_cap_t to the ulong array to print to
 666          * userspace if this is a read.
 667          */
 668         spin_lock(&umh_sysctl_lock);
 669         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
 670                 if (table->data == CAP_BSET)
 671                         cap_array[i] = usermodehelper_bset.cap[i];
 672                 else if (table->data == CAP_PI)
 673                         cap_array[i] = usermodehelper_inheritable.cap[i];
 674                 else
 675                         BUG();
 676         }
 677         spin_unlock(&umh_sysctl_lock);
 678
 679         t = *table;
 680         t.data = &cap_array;
 681
 682         /*
 683          * actually read or write and array of ulongs from userspace.  Remember
 684          * these are least significant 32 bits first
 685          */
 686         err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
 687         if (err < 0)
 688                 return err;
 689
 690         /*
 691          * convert from the sysctl array of ulongs to the kernel_cap_t
 692          * internal representation
 693          */
 694         for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
 695                 new_cap.cap[i] = cap_array[i];
 696
 697         /*
 698          * Drop everything not in the new_cap (but don't add things)
 699          */
 700         if (write) {
 701                 spin_lock(&umh_sysctl_lock);
 702                 if (table->data == CAP_BSET)
 703                         usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
 704                 if (table->data == CAP_PI)
 705                         usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
 706                 spin_unlock(&umh_sysctl_lock);
 707         }
 708
 709         return 0;
 710 }
 711
 712 void __exit_umh(struct task_struct *tsk)
 713 {
 714         struct umh_info *info;
 715         pid_t pid = tsk->pid;
 716
 717         mutex_lock(&umh_list_lock);
 718         list_for_each_entry(info, &umh_list, list) {
 719                 if (info->pid == pid) {
 720                         list_del(&info->list);
 721                         mutex_unlock(&umh_list_lock);
 722                         goto out;
 723                 }
 724         }
 725         mutex_unlock(&umh_list_lock);
 726         return;
 727 out:
 728         if (info->cleanup)
 729                 info->cleanup(info);
 730 }
 731
 732 struct ctl_table usermodehelper_table[] = {
 733         {
 734                 .procname       = "bset",
 735                 .data           = CAP_BSET,
 736                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 737                 .mode           = 0600,
 738                 .proc_handler   = proc_cap_handler,
 739         },
 740         {
 741                 .procname       = "inheritable",
 742                 .data           = CAP_PI,
 743                 .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
 744                 .mode           = 0600,
 745                 .proc_handler   = proc_cap_handler,
 746         },
 747         { }
 748 };