| 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 | va_start(args, fmt); |
| 151 | ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args); |
| 152 | va_end(args); |
| 153 | if (ret >= MODULE_NAME_LEN) |
| 154 | return -ENAMETOOLONG; |
| 155 | |
| 156 | ret = security_kernel_module_request(module_name); |
| 157 | if (ret) |
| 158 | return ret; |
| 159 | |
| 160 | /* If modprobe needs a service that is in a module, we get a recursive |
| 161 | * loop. Limit the number of running kmod threads to max_threads/2 or |
| 162 | * MAX_KMOD_CONCURRENT, whichever is the smaller. A cleaner method |
| 163 | * would be to run the parents of this process, counting how many times |
| 164 | * kmod was invoked. That would mean accessing the internals of the |
| 165 | * process tables to get the command line, proc_pid_cmdline is static |
| 166 | * and it is not worth changing the proc code just to handle this case. |
| 167 | * KAO. |
| 168 | * |
| 169 | * "trace the ppid" is simple, but will fail if someone's |
| 170 | * parent exits. I think this is as good as it gets. --RR |
| 171 | */ |
| 172 | max_modprobes = min(max_threads/2, MAX_KMOD_CONCURRENT); |
| 173 | atomic_inc(&kmod_concurrent); |
| 174 | if (atomic_read(&kmod_concurrent) > max_modprobes) { |
| 175 | /* We may be blaming an innocent here, but unlikely */ |
| 176 | if (kmod_loop_msg < 5) { |
| 177 | printk(KERN_ERR |
| 178 | "request_module: runaway loop modprobe %s\n", |
| 179 | module_name); |
| 180 | kmod_loop_msg++; |
| 181 | } |
| 182 | atomic_dec(&kmod_concurrent); |
| 183 | return -ENOMEM; |
| 184 | } |
| 185 | |
| 186 | trace_module_request(module_name, wait, _RET_IP_); |
| 187 | |
| 188 | ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); |
| 189 | |
| 190 | atomic_dec(&kmod_concurrent); |
| 191 | return ret; |
| 192 | } |
| 193 | EXPORT_SYMBOL(__request_module); |
| 194 | #endif /* CONFIG_MODULES */ |
| 195 | |
| 196 | /* |
| 197 | * This is the task which runs the usermode application |
| 198 | */ |
| 199 | static int ____call_usermodehelper(void *data) |
| 200 | { |
| 201 | struct subprocess_info *sub_info = data; |
| 202 | struct cred *new; |
| 203 | int retval; |
| 204 | |
| 205 | spin_lock_irq(¤t->sighand->siglock); |
| 206 | flush_signal_handlers(current, 1); |
| 207 | spin_unlock_irq(¤t->sighand->siglock); |
| 208 | |
| 209 | /* We can run anywhere, unlike our parent keventd(). */ |
| 210 | set_cpus_allowed_ptr(current, cpu_all_mask); |
| 211 | |
| 212 | /* |
| 213 | * Our parent is keventd, which runs with elevated scheduling priority. |
| 214 | * Avoid propagating that into the userspace child. |
| 215 | */ |
| 216 | set_user_nice(current, 0); |
| 217 | |
| 218 | retval = -ENOMEM; |
| 219 | new = prepare_kernel_cred(current); |
| 220 | if (!new) |
| 221 | goto fail; |
| 222 | |
| 223 | spin_lock(&umh_sysctl_lock); |
| 224 | new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset); |
| 225 | new->cap_inheritable = cap_intersect(usermodehelper_inheritable, |
| 226 | new->cap_inheritable); |
| 227 | spin_unlock(&umh_sysctl_lock); |
| 228 | |
| 229 | if (sub_info->init) { |
| 230 | retval = sub_info->init(sub_info, new); |
| 231 | if (retval) { |
| 232 | abort_creds(new); |
| 233 | goto fail; |
| 234 | } |
| 235 | } |
| 236 | |
| 237 | commit_creds(new); |
| 238 | |
| 239 | retval = do_execve(sub_info->path, |
| 240 | (const char __user *const __user *)sub_info->argv, |
| 241 | (const char __user *const __user *)sub_info->envp); |
| 242 | if (!retval) |
| 243 | return 0; |
| 244 | |
| 245 | /* Exec failed? */ |
| 246 | fail: |
| 247 | sub_info->retval = retval; |
| 248 | do_exit(0); |
| 249 | } |
| 250 | |
| 251 | static int call_helper(void *data) |
| 252 | { |
| 253 | /* Worker thread started blocking khelper thread. */ |
| 254 | kmod_thread_locker = current; |
| 255 | return ____call_usermodehelper(data); |
| 256 | } |
| 257 | |
| 258 | static void call_usermodehelper_freeinfo(struct subprocess_info *info) |
| 259 | { |
| 260 | if (info->cleanup) |
| 261 | (*info->cleanup)(info); |
| 262 | kfree(info); |
| 263 | } |
| 264 | |
| 265 | static void umh_complete(struct subprocess_info *sub_info) |
| 266 | { |
| 267 | struct completion *comp = xchg(&sub_info->complete, NULL); |
| 268 | /* |
| 269 | * See call_usermodehelper_exec(). If xchg() returns NULL |
| 270 | * we own sub_info, the UMH_KILLABLE caller has gone away. |
| 271 | */ |
| 272 | if (comp) |
| 273 | complete(comp); |
| 274 | else |
| 275 | call_usermodehelper_freeinfo(sub_info); |
| 276 | } |
| 277 | |
| 278 | /* Keventd can't block, but this (a child) can. */ |
| 279 | static int wait_for_helper(void *data) |
| 280 | { |
| 281 | struct subprocess_info *sub_info = data; |
| 282 | pid_t pid; |
| 283 | |
| 284 | /* If SIGCLD is ignored sys_wait4 won't populate the status. */ |
| 285 | spin_lock_irq(¤t->sighand->siglock); |
| 286 | current->sighand->action[SIGCHLD-1].sa.sa_handler = SIG_DFL; |
| 287 | spin_unlock_irq(¤t->sighand->siglock); |
| 288 | |
| 289 | pid = kernel_thread(____call_usermodehelper, sub_info, SIGCHLD); |
| 290 | if (pid < 0) { |
| 291 | sub_info->retval = pid; |
| 292 | } else { |
| 293 | int ret = -ECHILD; |
| 294 | /* |
| 295 | * Normally it is bogus to call wait4() from in-kernel because |
| 296 | * wait4() wants to write the exit code to a userspace address. |
| 297 | * But wait_for_helper() always runs as keventd, and put_user() |
| 298 | * to a kernel address works OK for kernel threads, due to their |
| 299 | * having an mm_segment_t which spans the entire address space. |
| 300 | * |
| 301 | * Thus the __user pointer cast is valid here. |
| 302 | */ |
| 303 | sys_wait4(pid, (int __user *)&ret, 0, NULL); |
| 304 | |
| 305 | /* |
| 306 | * If ret is 0, either ____call_usermodehelper failed and the |
| 307 | * real error code is already in sub_info->retval or |
| 308 | * sub_info->retval is 0 anyway, so don't mess with it then. |
| 309 | */ |
| 310 | if (ret) |
| 311 | sub_info->retval = ret; |
| 312 | } |
| 313 | |
| 314 | umh_complete(sub_info); |
| 315 | do_exit(0); |
| 316 | } |
| 317 | |
| 318 | /* This is run by khelper thread */ |
| 319 | static void __call_usermodehelper(struct work_struct *work) |
| 320 | { |
| 321 | struct subprocess_info *sub_info = |
| 322 | container_of(work, struct subprocess_info, work); |
| 323 | int wait = sub_info->wait & ~UMH_KILLABLE; |
| 324 | pid_t pid; |
| 325 | |
| 326 | /* CLONE_VFORK: wait until the usermode helper has execve'd |
| 327 | * successfully We need the data structures to stay around |
| 328 | * until that is done. */ |
| 329 | if (wait == UMH_WAIT_PROC) |
| 330 | pid = kernel_thread(wait_for_helper, sub_info, |
| 331 | CLONE_FS | CLONE_FILES | SIGCHLD); |
| 332 | else { |
| 333 | pid = kernel_thread(call_helper, sub_info, |
| 334 | CLONE_VFORK | SIGCHLD); |
| 335 | /* Worker thread stopped blocking khelper thread. */ |
| 336 | kmod_thread_locker = NULL; |
| 337 | } |
| 338 | |
| 339 | switch (wait) { |
| 340 | case UMH_NO_WAIT: |
| 341 | call_usermodehelper_freeinfo(sub_info); |
| 342 | break; |
| 343 | |
| 344 | case UMH_WAIT_PROC: |
| 345 | if (pid > 0) |
| 346 | break; |
| 347 | /* FALLTHROUGH */ |
| 348 | case UMH_WAIT_EXEC: |
| 349 | if (pid < 0) |
| 350 | sub_info->retval = pid; |
| 351 | umh_complete(sub_info); |
| 352 | } |
| 353 | } |
| 354 | |
| 355 | /* |
| 356 | * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY |
| 357 | * (used for preventing user land processes from being created after the user |
| 358 | * land has been frozen during a system-wide hibernation or suspend operation). |
| 359 | * Should always be manipulated under umhelper_sem acquired for write. |
| 360 | */ |
| 361 | static enum umh_disable_depth usermodehelper_disabled = UMH_DISABLED; |
| 362 | |
| 363 | /* Number of helpers running */ |
| 364 | static atomic_t running_helpers = ATOMIC_INIT(0); |
| 365 | |
| 366 | /* |
| 367 | * Wait queue head used by usermodehelper_disable() to wait for all running |
| 368 | * helpers to finish. |
| 369 | */ |
| 370 | static DECLARE_WAIT_QUEUE_HEAD(running_helpers_waitq); |
| 371 | |
| 372 | /* |
| 373 | * Used by usermodehelper_read_lock_wait() to wait for usermodehelper_disabled |
| 374 | * to become 'false'. |
| 375 | */ |
| 376 | static DECLARE_WAIT_QUEUE_HEAD(usermodehelper_disabled_waitq); |
| 377 | |
| 378 | /* |
| 379 | * Time to wait for running_helpers to become zero before the setting of |
| 380 | * usermodehelper_disabled in usermodehelper_disable() fails |
| 381 | */ |
| 382 | #define RUNNING_HELPERS_TIMEOUT (5 * HZ) |
| 383 | |
| 384 | int usermodehelper_read_trylock(void) |
| 385 | { |
| 386 | DEFINE_WAIT(wait); |
| 387 | int ret = 0; |
| 388 | |
| 389 | down_read(&umhelper_sem); |
| 390 | for (;;) { |
| 391 | prepare_to_wait(&usermodehelper_disabled_waitq, &wait, |
| 392 | TASK_INTERRUPTIBLE); |
| 393 | if (!usermodehelper_disabled) |
| 394 | break; |
| 395 | |
| 396 | if (usermodehelper_disabled == UMH_DISABLED) |
| 397 | ret = -EAGAIN; |
| 398 | |
| 399 | up_read(&umhelper_sem); |
| 400 | |
| 401 | if (ret) |
| 402 | break; |
| 403 | |
| 404 | schedule(); |
| 405 | try_to_freeze(); |
| 406 | |
| 407 | down_read(&umhelper_sem); |
| 408 | } |
| 409 | finish_wait(&usermodehelper_disabled_waitq, &wait); |
| 410 | return ret; |
| 411 | } |
| 412 | EXPORT_SYMBOL_GPL(usermodehelper_read_trylock); |
| 413 | |
| 414 | long usermodehelper_read_lock_wait(long timeout) |
| 415 | { |
| 416 | DEFINE_WAIT(wait); |
| 417 | |
| 418 | if (timeout < 0) |
| 419 | return -EINVAL; |
| 420 | |
| 421 | down_read(&umhelper_sem); |
| 422 | for (;;) { |
| 423 | prepare_to_wait(&usermodehelper_disabled_waitq, &wait, |
| 424 | TASK_UNINTERRUPTIBLE); |
| 425 | if (!usermodehelper_disabled) |
| 426 | break; |
| 427 | |
| 428 | up_read(&umhelper_sem); |
| 429 | |
| 430 | timeout = schedule_timeout(timeout); |
| 431 | if (!timeout) |
| 432 | break; |
| 433 | |
| 434 | down_read(&umhelper_sem); |
| 435 | } |
| 436 | finish_wait(&usermodehelper_disabled_waitq, &wait); |
| 437 | return timeout; |
| 438 | } |
| 439 | EXPORT_SYMBOL_GPL(usermodehelper_read_lock_wait); |
| 440 | |
| 441 | void usermodehelper_read_unlock(void) |
| 442 | { |
| 443 | up_read(&umhelper_sem); |
| 444 | } |
| 445 | EXPORT_SYMBOL_GPL(usermodehelper_read_unlock); |
| 446 | |
| 447 | /** |
| 448 | * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled. |
| 449 | * @depth: New value to assign to usermodehelper_disabled. |
| 450 | * |
| 451 | * Change the value of usermodehelper_disabled (under umhelper_sem locked for |
| 452 | * writing) and wakeup tasks waiting for it to change. |
| 453 | */ |
| 454 | void __usermodehelper_set_disable_depth(enum umh_disable_depth depth) |
| 455 | { |
| 456 | down_write(&umhelper_sem); |
| 457 | usermodehelper_disabled = depth; |
| 458 | wake_up(&usermodehelper_disabled_waitq); |
| 459 | up_write(&umhelper_sem); |
| 460 | } |
| 461 | EXPORT_SYMBOL_GPL(__usermodehelper_set_disable_depth); |
| 462 | |
| 463 | /** |
| 464 | * __usermodehelper_disable - Prevent new helpers from being started. |
| 465 | * @depth: New value to assign to usermodehelper_disabled. |
| 466 | * |
| 467 | * Set usermodehelper_disabled to @depth and wait for running helpers to exit. |
| 468 | */ |
| 469 | int __usermodehelper_disable(enum umh_disable_depth depth) |
| 470 | { |
| 471 | long retval; |
| 472 | |
| 473 | if (!depth) |
| 474 | return -EINVAL; |
| 475 | |
| 476 | down_write(&umhelper_sem); |
| 477 | usermodehelper_disabled = depth; |
| 478 | up_write(&umhelper_sem); |
| 479 | |
| 480 | /* |
| 481 | * From now on call_usermodehelper_exec() won't start any new |
| 482 | * helpers, so it is sufficient if running_helpers turns out to |
| 483 | * be zero at one point (it may be increased later, but that |
| 484 | * doesn't matter). |
| 485 | */ |
| 486 | retval = wait_event_timeout(running_helpers_waitq, |
| 487 | atomic_read(&running_helpers) == 0, |
| 488 | RUNNING_HELPERS_TIMEOUT); |
| 489 | if (retval) |
| 490 | return 0; |
| 491 | |
| 492 | __usermodehelper_set_disable_depth(UMH_ENABLED); |
| 493 | return -EAGAIN; |
| 494 | } |
| 495 | EXPORT_SYMBOL_GPL(__usermodehelper_disable); |
| 496 | |
| 497 | static void helper_lock(void) |
| 498 | { |
| 499 | atomic_inc(&running_helpers); |
| 500 | smp_mb__after_atomic_inc(); |
| 501 | } |
| 502 | |
| 503 | static void helper_unlock(void) |
| 504 | { |
| 505 | if (atomic_dec_and_test(&running_helpers)) |
| 506 | wake_up(&running_helpers_waitq); |
| 507 | } |
| 508 | |
| 509 | /** |
| 510 | * call_usermodehelper_setup - prepare to call a usermode helper |
| 511 | * @path: path to usermode executable |
| 512 | * @argv: arg vector for process |
| 513 | * @envp: environment for process |
| 514 | * @gfp_mask: gfp mask for memory allocation |
| 515 | * @cleanup: a cleanup function |
| 516 | * @init: an init function |
| 517 | * @data: arbitrary context sensitive data |
| 518 | * |
| 519 | * Returns either %NULL on allocation failure, or a subprocess_info |
| 520 | * structure. This should be passed to call_usermodehelper_exec to |
| 521 | * exec the process and free the structure. |
| 522 | * |
| 523 | * The init function is used to customize the helper process prior to |
| 524 | * exec. A non-zero return code causes the process to error out, exit, |
| 525 | * and return the failure to the calling process |
| 526 | * |
| 527 | * The cleanup function is just before ethe subprocess_info is about to |
| 528 | * be freed. This can be used for freeing the argv and envp. The |
| 529 | * Function must be runnable in either a process context or the |
| 530 | * context in which call_usermodehelper_exec is called. |
| 531 | */ |
| 532 | struct subprocess_info *call_usermodehelper_setup(char *path, char **argv, |
| 533 | char **envp, gfp_t gfp_mask, |
| 534 | int (*init)(struct subprocess_info *info, struct cred *new), |
| 535 | void (*cleanup)(struct subprocess_info *info), |
| 536 | void *data) |
| 537 | { |
| 538 | struct subprocess_info *sub_info; |
| 539 | sub_info = kzalloc(sizeof(struct subprocess_info), gfp_mask); |
| 540 | if (!sub_info) |
| 541 | goto out; |
| 542 | |
| 543 | INIT_WORK(&sub_info->work, __call_usermodehelper); |
| 544 | sub_info->path = path; |
| 545 | sub_info->argv = argv; |
| 546 | sub_info->envp = envp; |
| 547 | |
| 548 | sub_info->cleanup = cleanup; |
| 549 | sub_info->init = init; |
| 550 | sub_info->data = data; |
| 551 | out: |
| 552 | return sub_info; |
| 553 | } |
| 554 | EXPORT_SYMBOL(call_usermodehelper_setup); |
| 555 | |
| 556 | /** |
| 557 | * call_usermodehelper_exec - start a usermode application |
| 558 | * @sub_info: information about the subprocessa |
| 559 | * @wait: wait for the application to finish and return status. |
| 560 | * when UMH_NO_WAIT don't wait at all, but you get no useful error back |
| 561 | * when the program couldn't be exec'ed. This makes it safe to call |
| 562 | * from interrupt context. |
| 563 | * |
| 564 | * Runs a user-space application. The application is started |
| 565 | * asynchronously if wait is not set, and runs as a child of keventd. |
| 566 | * (ie. it runs with full root capabilities). |
| 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 | helper_lock(); |
| 574 | if (!sub_info->path) { |
| 575 | retval = -EINVAL; |
| 576 | goto out; |
| 577 | } |
| 578 | |
| 579 | if (sub_info->path[0] == '\0') |
| 580 | goto out; |
| 581 | |
| 582 | if (!khelper_wq || usermodehelper_disabled) { |
| 583 | pr_warn("[%s] retval(%d), usermodehelper_disabled(%d)\n", __func__, retval, usermodehelper_disabled); |
| 584 | retval = -EBUSY; |
| 585 | goto out; |
| 586 | } |
| 587 | /* |
| 588 | * Worker thread must not wait for khelper thread at below |
| 589 | * wait_for_completion() if the thread was created with CLONE_VFORK |
| 590 | * flag, for khelper thread is already waiting for the thread at |
| 591 | * wait_for_completion() in do_fork(). |
| 592 | */ |
| 593 | if (wait != UMH_NO_WAIT && current == kmod_thread_locker) { |
| 594 | retval = -EBUSY; |
| 595 | goto out; |
| 596 | } |
| 597 | |
| 598 | sub_info->complete = &done; |
| 599 | sub_info->wait = wait; |
| 600 | |
| 601 | queue_work(khelper_wq, &sub_info->work); |
| 602 | if (wait == UMH_NO_WAIT) /* task has freed sub_info */ |
| 603 | goto unlock; |
| 604 | |
| 605 | if (wait & UMH_KILLABLE) { |
| 606 | retval = wait_for_completion_killable(&done); |
| 607 | if (!retval) |
| 608 | goto wait_done; |
| 609 | |
| 610 | /* umh_complete() will see NULL and free sub_info */ |
| 611 | if (xchg(&sub_info->complete, NULL)) |
| 612 | goto unlock; |
| 613 | /* fallthrough, umh_complete() was already called */ |
| 614 | } |
| 615 | |
| 616 | wait_for_completion(&done); |
| 617 | wait_done: |
| 618 | retval = sub_info->retval; |
| 619 | out: |
| 620 | call_usermodehelper_freeinfo(sub_info); |
| 621 | unlock: |
| 622 | helper_unlock(); |
| 623 | return retval; |
| 624 | } |
| 625 | EXPORT_SYMBOL(call_usermodehelper_exec); |
| 626 | |
| 627 | /** |
| 628 | * call_usermodehelper() - prepare and start a usermode application |
| 629 | * @path: path to usermode executable |
| 630 | * @argv: arg vector for process |
| 631 | * @envp: environment for process |
| 632 | * @wait: wait for the application to finish and return status. |
| 633 | * when UMH_NO_WAIT don't wait at all, but you get no useful error back |
| 634 | * when the program couldn't be exec'ed. This makes it safe to call |
| 635 | * from interrupt context. |
| 636 | * |
| 637 | * This function is the equivalent to use call_usermodehelper_setup() and |
| 638 | * call_usermodehelper_exec(). |
| 639 | */ |
| 640 | int call_usermodehelper(char *path, char **argv, char **envp, int wait) |
| 641 | { |
| 642 | struct subprocess_info *info; |
| 643 | gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL; |
| 644 | |
| 645 | info = call_usermodehelper_setup(path, argv, envp, gfp_mask, |
| 646 | NULL, NULL, NULL); |
| 647 | if (info == NULL) |
| 648 | return -ENOMEM; |
| 649 | |
| 650 | return call_usermodehelper_exec(info, wait); |
| 651 | } |
| 652 | EXPORT_SYMBOL(call_usermodehelper); |
| 653 | |
| 654 | static int proc_cap_handler(struct ctl_table *table, int write, |
| 655 | void __user *buffer, size_t *lenp, loff_t *ppos) |
| 656 | { |
| 657 | struct ctl_table t; |
| 658 | unsigned long cap_array[_KERNEL_CAPABILITY_U32S]; |
| 659 | kernel_cap_t new_cap; |
| 660 | int err, i; |
| 661 | |
| 662 | if (write && (!capable(CAP_SETPCAP) || |
| 663 | !capable(CAP_SYS_MODULE))) |
| 664 | return -EPERM; |
| 665 | |
| 666 | /* |
| 667 | * convert from the global kernel_cap_t to the ulong array to print to |
| 668 | * userspace if this is a read. |
| 669 | */ |
| 670 | spin_lock(&umh_sysctl_lock); |
| 671 | for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) { |
| 672 | if (table->data == CAP_BSET) |
| 673 | cap_array[i] = usermodehelper_bset.cap[i]; |
| 674 | else if (table->data == CAP_PI) |
| 675 | cap_array[i] = usermodehelper_inheritable.cap[i]; |
| 676 | else |
| 677 | BUG(); |
| 678 | } |
| 679 | spin_unlock(&umh_sysctl_lock); |
| 680 | |
| 681 | t = *table; |
| 682 | t.data = &cap_array; |
| 683 | |
| 684 | /* |
| 685 | * actually read or write and array of ulongs from userspace. Remember |
| 686 | * these are least significant 32 bits first |
| 687 | */ |
| 688 | err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos); |
| 689 | if (err < 0) |
| 690 | return err; |
| 691 | |
| 692 | /* |
| 693 | * convert from the sysctl array of ulongs to the kernel_cap_t |
| 694 | * internal representation |
| 695 | */ |
| 696 | for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++) |
| 697 | new_cap.cap[i] = cap_array[i]; |
| 698 | |
| 699 | /* |
| 700 | * Drop everything not in the new_cap (but don't add things) |
| 701 | */ |
| 702 | spin_lock(&umh_sysctl_lock); |
| 703 | if (write) { |
| 704 | if (table->data == CAP_BSET) |
| 705 | usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap); |
| 706 | if (table->data == CAP_PI) |
| 707 | usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap); |
| 708 | } |
| 709 | spin_unlock(&umh_sysctl_lock); |
| 710 | |
| 711 | return 0; |
| 712 | } |
| 713 | |
| 714 | struct ctl_table usermodehelper_table[] = { |
| 715 | { |
| 716 | .procname = "bset", |
| 717 | .data = CAP_BSET, |
| 718 | .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long), |
| 719 | .mode = 0600, |
| 720 | .proc_handler = proc_cap_handler, |
| 721 | }, |
| 722 | { |
| 723 | .procname = "inheritable", |
| 724 | .data = CAP_PI, |
| 725 | .maxlen = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long), |
| 726 | .mode = 0600, |
| 727 | .proc_handler = proc_cap_handler, |
| 728 | }, |
| 729 | { } |
| 730 | }; |
| 731 | |
| 732 | void __init usermodehelper_init(void) |
| 733 | { |
| 734 | khelper_wq = create_singlethread_workqueue("khelper"); |
| 735 | BUG_ON(!khelper_wq); |
| 736 | } |