1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/kernel/seccomp.c 4 * 5 * Copyright 2004-2005 Andrea Arcangeli <[email protected]> 6 * 7 * Copyright (C) 2012 Google, Inc. 8 * Will Drewry <[email protected]> 9 * 10 * This defines a simple but solid secure-computing facility. 11 * 12 * Mode 1 uses a fixed list of allowed system calls. 13 * Mode 2 allows user-defined system call filters in the form 14 * of Berkeley Packet Filters/Linux Socket Filters. 15 */ 16 #define pr_fmt(fmt) "seccomp: " fmt 17 18 #include <linux/refcount.h> 19 #include <linux/audit.h> 20 #include <linux/compat.h> 21 #include <linux/coredump.h> 22 #include <linux/kmemleak.h> 23 #include <linux/nospec.h> 24 #include <linux/prctl.h> 25 #include <linux/sched.h> 26 #include <linux/sched/task_stack.h> 27 #include <linux/seccomp.h> 28 #include <linux/slab.h> 29 #include <linux/syscalls.h> 30 #include <linux/sysctl.h> 31 32 #include <asm/syscall.h> 33 34 /* Not exposed in headers: strictly internal use only. */ 35 #define SECCOMP_MODE_DEAD (SECCOMP_MODE_FILTER + 1) 36 37 #ifdef CONFIG_SECCOMP_FILTER 38 #include <linux/file.h> 39 #include <linux/filter.h> 40 #include <linux/pid.h> 41 #include <linux/ptrace.h> 42 #include <linux/capability.h> 43 #include <linux/uaccess.h> 44 #include <linux/anon_inodes.h> 45 #include <linux/lockdep.h> 46 47 /* 48 * When SECCOMP_IOCTL_NOTIF_ID_VALID was first introduced, it had the 49 * wrong direction flag in the ioctl number. This is the broken one, 50 * which the kernel needs to keep supporting until all userspaces stop 51 * using the wrong command number. 52 */ 53 #define SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR SECCOMP_IOR(2, __u64) 54 55 enum notify_state { 56 SECCOMP_NOTIFY_INIT, 57 SECCOMP_NOTIFY_SENT, 58 SECCOMP_NOTIFY_REPLIED, 59 }; 60 61 struct seccomp_knotif { 62 /* The struct pid of the task whose filter triggered the notification */ 63 struct task_struct *task; 64 65 /* The "cookie" for this request; this is unique for this filter. */ 66 u64 id; 67 68 /* 69 * The seccomp data. This pointer is valid the entire time this 70 * notification is active, since it comes from __seccomp_filter which 71 * eclipses the entire lifecycle here. 72 */ 73 const struct seccomp_data *data; 74 75 /* 76 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a 77 * struct seccomp_knotif is created and starts out in INIT. Once the 78 * handler reads the notification off of an FD, it transitions to SENT. 79 * If a signal is received the state transitions back to INIT and 80 * another message is sent. When the userspace handler replies, state 81 * transitions to REPLIED. 82 */ 83 enum notify_state state; 84 85 /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */ 86 int error; 87 long val; 88 u32 flags; 89 90 /* 91 * Signals when this has changed states, such as the listener 92 * dying, a new seccomp addfd message, or changing to REPLIED 93 */ 94 struct completion ready; 95 96 struct list_head list; 97 98 /* outstanding addfd requests */ 99 struct list_head addfd; 100 }; 101 102 /** 103 * struct seccomp_kaddfd - container for seccomp_addfd ioctl messages 104 * 105 * @file: A reference to the file to install in the other task 106 * @fd: The fd number to install it at. If the fd number is -1, it means the 107 * installing process should allocate the fd as normal. 108 * @flags: The flags for the new file descriptor. At the moment, only O_CLOEXEC 109 * is allowed. 110 * @ioctl_flags: The flags used for the seccomp_addfd ioctl. 111 * @setfd: whether or not SECCOMP_ADDFD_FLAG_SETFD was set during notify_addfd 112 * @ret: The return value of the installing process. It is set to the fd num 113 * upon success (>= 0). 114 * @completion: Indicates that the installing process has completed fd 115 * installation, or gone away (either due to successful 116 * reply, or signal) 117 * @list: list_head for chaining seccomp_kaddfd together. 118 * 119 */ 120 struct seccomp_kaddfd { 121 struct file *file; 122 int fd; 123 unsigned int flags; 124 __u32 ioctl_flags; 125 126 union { 127 bool setfd; 128 /* To only be set on reply */ 129 int ret; 130 }; 131 struct completion completion; 132 struct list_head list; 133 }; 134 135 /** 136 * struct notification - container for seccomp userspace notifications. Since 137 * most seccomp filters will not have notification listeners attached and this 138 * structure is fairly large, we store the notification-specific stuff in a 139 * separate structure. 140 * 141 * @requests: A semaphore that users of this notification can wait on for 142 * changes. Actual reads and writes are still controlled with 143 * filter->notify_lock. 144 * @flags: A set of SECCOMP_USER_NOTIF_FD_* flags. 145 * @next_id: The id of the next request. 146 * @notifications: A list of struct seccomp_knotif elements. 147 */ 148 149 struct notification { 150 atomic_t requests; 151 u32 flags; 152 u64 next_id; 153 struct list_head notifications; 154 }; 155 156 #ifdef SECCOMP_ARCH_NATIVE 157 /** 158 * struct action_cache - per-filter cache of seccomp actions per 159 * arch/syscall pair 160 * 161 * @allow_native: A bitmap where each bit represents whether the 162 * filter will always allow the syscall, for the 163 * native architecture. 164 * @allow_compat: A bitmap where each bit represents whether the 165 * filter will always allow the syscall, for the 166 * compat architecture. 167 */ 168 struct action_cache { 169 DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR); 170 #ifdef SECCOMP_ARCH_COMPAT 171 DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR); 172 #endif 173 }; 174 #else 175 struct action_cache { }; 176 177 static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter, 178 const struct seccomp_data *sd) 179 { 180 return false; 181 } 182 183 static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter) 184 { 185 } 186 #endif /* SECCOMP_ARCH_NATIVE */ 187 188 /** 189 * struct seccomp_filter - container for seccomp BPF programs 190 * 191 * @refs: Reference count to manage the object lifetime. 192 * A filter's reference count is incremented for each directly 193 * attached task, once for the dependent filter, and if 194 * requested for the user notifier. When @refs reaches zero, 195 * the filter can be freed. 196 * @users: A filter's @users count is incremented for each directly 197 * attached task (filter installation, fork(), thread_sync), 198 * and once for the dependent filter (tracked in filter->prev). 199 * When it reaches zero it indicates that no direct or indirect 200 * users of that filter exist. No new tasks can get associated with 201 * this filter after reaching 0. The @users count is always smaller 202 * or equal to @refs. Hence, reaching 0 for @users does not mean 203 * the filter can be freed. 204 * @cache: cache of arch/syscall mappings to actions 205 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged 206 * @wait_killable_recv: Put notifying process in killable state once the 207 * notification is received by the userspace listener. 208 * @prev: points to a previously installed, or inherited, filter 209 * @prog: the BPF program to evaluate 210 * @notif: the struct that holds all notification related information 211 * @notify_lock: A lock for all notification-related accesses. 212 * @wqh: A wait queue for poll if a notifier is in use. 213 * 214 * seccomp_filter objects are organized in a tree linked via the @prev 215 * pointer. For any task, it appears to be a singly-linked list starting 216 * with current->seccomp.filter, the most recently attached or inherited filter. 217 * However, multiple filters may share a @prev node, by way of fork(), which 218 * results in a unidirectional tree existing in memory. This is similar to 219 * how namespaces work. 220 * 221 * seccomp_filter objects should never be modified after being attached 222 * to a task_struct (other than @refs). 223 */ 224 struct seccomp_filter { 225 refcount_t refs; 226 refcount_t users; 227 bool log; 228 bool wait_killable_recv; 229 struct action_cache cache; 230 struct seccomp_filter *prev; 231 struct bpf_prog *prog; 232 struct notification *notif; 233 struct mutex notify_lock; 234 wait_queue_head_t wqh; 235 }; 236 237 /* Limit any path through the tree to 256KB worth of instructions. */ 238 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) 239 240 /* 241 * Endianness is explicitly ignored and left for BPF program authors to manage 242 * as per the specific architecture. 243 */ 244 static void populate_seccomp_data(struct seccomp_data *sd) 245 { 246 /* 247 * Instead of using current_pt_reg(), we're already doing the work 248 * to safely fetch "current", so just use "task" everywhere below. 249 */ 250 struct task_struct *task = current; 251 struct pt_regs *regs = task_pt_regs(task); 252 unsigned long args[6]; 253 254 sd->nr = syscall_get_nr(task, regs); 255 sd->arch = syscall_get_arch(task); 256 syscall_get_arguments(task, regs, args); 257 sd->args[0] = args[0]; 258 sd->args[1] = args[1]; 259 sd->args[2] = args[2]; 260 sd->args[3] = args[3]; 261 sd->args[4] = args[4]; 262 sd->args[5] = args[5]; 263 sd->instruction_pointer = KSTK_EIP(task); 264 } 265 266 /** 267 * seccomp_check_filter - verify seccomp filter code 268 * @filter: filter to verify 269 * @flen: length of filter 270 * 271 * Takes a previously checked filter (by bpf_check_classic) and 272 * redirects all filter code that loads struct sk_buff data 273 * and related data through seccomp_bpf_load. It also 274 * enforces length and alignment checking of those loads. 275 * 276 * Returns 0 if the rule set is legal or -EINVAL if not. 277 */ 278 static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) 279 { 280 int pc; 281 for (pc = 0; pc < flen; pc++) { 282 struct sock_filter *ftest = &filter[pc]; 283 u16 code = ftest->code; 284 u32 k = ftest->k; 285 286 switch (code) { 287 case BPF_LD | BPF_W | BPF_ABS: 288 ftest->code = BPF_LDX | BPF_W | BPF_ABS; 289 /* 32-bit aligned and not out of bounds. */ 290 if (k >= sizeof(struct seccomp_data) || k & 3) 291 return -EINVAL; 292 continue; 293 case BPF_LD | BPF_W | BPF_LEN: 294 ftest->code = BPF_LD | BPF_IMM; 295 ftest->k = sizeof(struct seccomp_data); 296 continue; 297 case BPF_LDX | BPF_W | BPF_LEN: 298 ftest->code = BPF_LDX | BPF_IMM; 299 ftest->k = sizeof(struct seccomp_data); 300 continue; 301 /* Explicitly include allowed calls. */ 302 case BPF_RET | BPF_K: 303 case BPF_RET | BPF_A: 304 case BPF_ALU | BPF_ADD | BPF_K: 305 case BPF_ALU | BPF_ADD | BPF_X: 306 case BPF_ALU | BPF_SUB | BPF_K: 307 case BPF_ALU | BPF_SUB | BPF_X: 308 case BPF_ALU | BPF_MUL | BPF_K: 309 case BPF_ALU | BPF_MUL | BPF_X: 310 case BPF_ALU | BPF_DIV | BPF_K: 311 case BPF_ALU | BPF_DIV | BPF_X: 312 case BPF_ALU | BPF_AND | BPF_K: 313 case BPF_ALU | BPF_AND | BPF_X: 314 case BPF_ALU | BPF_OR | BPF_K: 315 case BPF_ALU | BPF_OR | BPF_X: 316 case BPF_ALU | BPF_XOR | BPF_K: 317 case BPF_ALU | BPF_XOR | BPF_X: 318 case BPF_ALU | BPF_LSH | BPF_K: 319 case BPF_ALU | BPF_LSH | BPF_X: 320 case BPF_ALU | BPF_RSH | BPF_K: 321 case BPF_ALU | BPF_RSH | BPF_X: 322 case BPF_ALU | BPF_NEG: 323 case BPF_LD | BPF_IMM: 324 case BPF_LDX | BPF_IMM: 325 case BPF_MISC | BPF_TAX: 326 case BPF_MISC | BPF_TXA: 327 case BPF_LD | BPF_MEM: 328 case BPF_LDX | BPF_MEM: 329 case BPF_ST: 330 case BPF_STX: 331 case BPF_JMP | BPF_JA: 332 case BPF_JMP | BPF_JEQ | BPF_K: 333 case BPF_JMP | BPF_JEQ | BPF_X: 334 case BPF_JMP | BPF_JGE | BPF_K: 335 case BPF_JMP | BPF_JGE | BPF_X: 336 case BPF_JMP | BPF_JGT | BPF_K: 337 case BPF_JMP | BPF_JGT | BPF_X: 338 case BPF_JMP | BPF_JSET | BPF_K: 339 case BPF_JMP | BPF_JSET | BPF_X: 340 continue; 341 default: 342 return -EINVAL; 343 } 344 } 345 return 0; 346 } 347 348 #ifdef SECCOMP_ARCH_NATIVE 349 static inline bool seccomp_cache_check_allow_bitmap(const void *bitmap, 350 size_t bitmap_size, 351 int syscall_nr) 352 { 353 if (unlikely(syscall_nr < 0 || syscall_nr >= bitmap_size)) 354 return false; 355 syscall_nr = array_index_nospec(syscall_nr, bitmap_size); 356 357 return test_bit(syscall_nr, bitmap); 358 } 359 360 /** 361 * seccomp_cache_check_allow - lookup seccomp cache 362 * @sfilter: The seccomp filter 363 * @sd: The seccomp data to lookup the cache with 364 * 365 * Returns true if the seccomp_data is cached and allowed. 366 */ 367 static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilter, 368 const struct seccomp_data *sd) 369 { 370 int syscall_nr = sd->nr; 371 const struct action_cache *cache = &sfilter->cache; 372 373 #ifndef SECCOMP_ARCH_COMPAT 374 /* A native-only architecture doesn't need to check sd->arch. */ 375 return seccomp_cache_check_allow_bitmap(cache->allow_native, 376 SECCOMP_ARCH_NATIVE_NR, 377 syscall_nr); 378 #else 379 if (likely(sd->arch == SECCOMP_ARCH_NATIVE)) 380 return seccomp_cache_check_allow_bitmap(cache->allow_native, 381 SECCOMP_ARCH_NATIVE_NR, 382 syscall_nr); 383 if (likely(sd->arch == SECCOMP_ARCH_COMPAT)) 384 return seccomp_cache_check_allow_bitmap(cache->allow_compat, 385 SECCOMP_ARCH_COMPAT_NR, 386 syscall_nr); 387 #endif /* SECCOMP_ARCH_COMPAT */ 388 389 WARN_ON_ONCE(true); 390 return false; 391 } 392 #endif /* SECCOMP_ARCH_NATIVE */ 393 394 #define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL))) 395 /** 396 * seccomp_run_filters - evaluates all seccomp filters against @sd 397 * @sd: optional seccomp data to be passed to filters 398 * @match: stores struct seccomp_filter that resulted in the return value, 399 * unless filter returned SECCOMP_RET_ALLOW, in which case it will 400 * be unchanged. 401 * 402 * Returns valid seccomp BPF response codes. 403 */ 404 static u32 seccomp_run_filters(const struct seccomp_data *sd, 405 struct seccomp_filter **match) 406 { 407 u32 ret = SECCOMP_RET_ALLOW; 408 /* Make sure cross-thread synced filter points somewhere sane. */ 409 struct seccomp_filter *f = 410 READ_ONCE(current->seccomp.filter); 411 412 /* Ensure unexpected behavior doesn't result in failing open. */ 413 if (WARN_ON(f == NULL)) 414 return SECCOMP_RET_KILL_PROCESS; 415 416 if (seccomp_cache_check_allow(f, sd)) 417 return SECCOMP_RET_ALLOW; 418 419 /* 420 * All filters in the list are evaluated and the lowest BPF return 421 * value always takes priority (ignoring the DATA). 422 */ 423 for (; f; f = f->prev) { 424 u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd); 425 426 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { 427 ret = cur_ret; 428 *match = f; 429 } 430 } 431 return ret; 432 } 433 #endif /* CONFIG_SECCOMP_FILTER */ 434 435 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) 436 { 437 assert_spin_locked(¤t->sighand->siglock); 438 439 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) 440 return false; 441 442 return true; 443 } 444 445 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } 446 447 static inline void seccomp_assign_mode(struct task_struct *task, 448 unsigned long seccomp_mode, 449 unsigned long flags) 450 { 451 assert_spin_locked(&task->sighand->siglock); 452 453 task->seccomp.mode = seccomp_mode; 454 /* 455 * Make sure SYSCALL_WORK_SECCOMP cannot be set before the mode (and 456 * filter) is set. 457 */ 458 smp_mb__before_atomic(); 459 /* Assume default seccomp processes want spec flaw mitigation. */ 460 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) 461 arch_seccomp_spec_mitigate(task); 462 set_task_syscall_work(task, SECCOMP); 463 } 464 465 #ifdef CONFIG_SECCOMP_FILTER 466 /* Returns 1 if the parent is an ancestor of the child. */ 467 static int is_ancestor(struct seccomp_filter *parent, 468 struct seccomp_filter *child) 469 { 470 /* NULL is the root ancestor. */ 471 if (parent == NULL) 472 return 1; 473 for (; child; child = child->prev) 474 if (child == parent) 475 return 1; 476 return 0; 477 } 478 479 /** 480 * seccomp_can_sync_threads: checks if all threads can be synchronized 481 * 482 * Expects sighand and cred_guard_mutex locks to be held. 483 * 484 * Returns 0 on success, -ve on error, or the pid of a thread which was 485 * either not in the correct seccomp mode or did not have an ancestral 486 * seccomp filter. 487 */ 488 static inline pid_t seccomp_can_sync_threads(void) 489 { 490 struct task_struct *thread, *caller; 491 492 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 493 assert_spin_locked(¤t->sighand->siglock); 494 495 /* Validate all threads being eligible for synchronization. */ 496 caller = current; 497 for_each_thread(caller, thread) { 498 pid_t failed; 499 500 /* Skip current, since it is initiating the sync. */ 501 if (thread == caller) 502 continue; 503 /* Skip exited threads. */ 504 if (thread->flags & PF_EXITING) 505 continue; 506 507 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || 508 (thread->seccomp.mode == SECCOMP_MODE_FILTER && 509 is_ancestor(thread->seccomp.filter, 510 caller->seccomp.filter))) 511 continue; 512 513 /* Return the first thread that cannot be synchronized. */ 514 failed = task_pid_vnr(thread); 515 /* If the pid cannot be resolved, then return -ESRCH */ 516 if (WARN_ON(failed == 0)) 517 failed = -ESRCH; 518 return failed; 519 } 520 521 return 0; 522 } 523 524 static inline void seccomp_filter_free(struct seccomp_filter *filter) 525 { 526 if (filter) { 527 bpf_prog_destroy(filter->prog); 528 kfree(filter); 529 } 530 } 531 532 static void __seccomp_filter_orphan(struct seccomp_filter *orig) 533 { 534 while (orig && refcount_dec_and_test(&orig->users)) { 535 if (waitqueue_active(&orig->wqh)) 536 wake_up_poll(&orig->wqh, EPOLLHUP); 537 orig = orig->prev; 538 } 539 } 540 541 static void __put_seccomp_filter(struct seccomp_filter *orig) 542 { 543 /* Clean up single-reference branches iteratively. */ 544 while (orig && refcount_dec_and_test(&orig->refs)) { 545 struct seccomp_filter *freeme = orig; 546 orig = orig->prev; 547 seccomp_filter_free(freeme); 548 } 549 } 550 551 static void __seccomp_filter_release(struct seccomp_filter *orig) 552 { 553 /* Notify about any unused filters in the task's former filter tree. */ 554 __seccomp_filter_orphan(orig); 555 /* Finally drop all references to the task's former tree. */ 556 __put_seccomp_filter(orig); 557 } 558 559 /** 560 * seccomp_filter_release - Detach the task from its filter tree, 561 * drop its reference count, and notify 562 * about unused filters 563 * 564 * @tsk: task the filter should be released from. 565 * 566 * This function should only be called when the task is exiting as 567 * it detaches it from its filter tree. PF_EXITING has to be set 568 * for the task. 569 */ 570 void seccomp_filter_release(struct task_struct *tsk) 571 { 572 struct seccomp_filter *orig; 573 574 if (WARN_ON((tsk->flags & PF_EXITING) == 0)) 575 return; 576 577 spin_lock_irq(&tsk->sighand->siglock); 578 orig = tsk->seccomp.filter; 579 /* Detach task from its filter tree. */ 580 tsk->seccomp.filter = NULL; 581 spin_unlock_irq(&tsk->sighand->siglock); 582 __seccomp_filter_release(orig); 583 } 584 585 /** 586 * seccomp_sync_threads: sets all threads to use current's filter 587 * 588 * @flags: SECCOMP_FILTER_FLAG_* flags to set during sync. 589 * 590 * Expects sighand and cred_guard_mutex locks to be held, and for 591 * seccomp_can_sync_threads() to have returned success already 592 * without dropping the locks. 593 * 594 */ 595 static inline void seccomp_sync_threads(unsigned long flags) 596 { 597 struct task_struct *thread, *caller; 598 599 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 600 assert_spin_locked(¤t->sighand->siglock); 601 602 /* Synchronize all threads. */ 603 caller = current; 604 for_each_thread(caller, thread) { 605 /* Skip current, since it needs no changes. */ 606 if (thread == caller) 607 continue; 608 609 /* 610 * Skip exited threads. seccomp_filter_release could have 611 * been already called for this task. 612 */ 613 if (thread->flags & PF_EXITING) 614 continue; 615 616 /* Get a task reference for the new leaf node. */ 617 get_seccomp_filter(caller); 618 619 /* 620 * Drop the task reference to the shared ancestor since 621 * current's path will hold a reference. (This also 622 * allows a put before the assignment.) 623 */ 624 __seccomp_filter_release(thread->seccomp.filter); 625 626 /* Make our new filter tree visible. */ 627 smp_store_release(&thread->seccomp.filter, 628 caller->seccomp.filter); 629 atomic_set(&thread->seccomp.filter_count, 630 atomic_read(&caller->seccomp.filter_count)); 631 632 /* 633 * Don't let an unprivileged task work around 634 * the no_new_privs restriction by creating 635 * a thread that sets it up, enters seccomp, 636 * then dies. 637 */ 638 if (task_no_new_privs(caller)) 639 task_set_no_new_privs(thread); 640 641 /* 642 * Opt the other thread into seccomp if needed. 643 * As threads are considered to be trust-realm 644 * equivalent (see ptrace_may_access), it is safe to 645 * allow one thread to transition the other. 646 */ 647 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) 648 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, 649 flags); 650 } 651 } 652 653 /** 654 * seccomp_prepare_filter: Prepares a seccomp filter for use. 655 * @fprog: BPF program to install 656 * 657 * Returns filter on success or an ERR_PTR on failure. 658 */ 659 static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) 660 { 661 struct seccomp_filter *sfilter; 662 int ret; 663 const bool save_orig = 664 #if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH_NATIVE) 665 true; 666 #else 667 false; 668 #endif 669 670 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) 671 return ERR_PTR(-EINVAL); 672 673 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); 674 675 /* 676 * Installing a seccomp filter requires that the task has 677 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. 678 * This avoids scenarios where unprivileged tasks can affect the 679 * behavior of privileged children. 680 */ 681 if (!task_no_new_privs(current) && 682 !ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN)) 683 return ERR_PTR(-EACCES); 684 685 /* Allocate a new seccomp_filter */ 686 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); 687 if (!sfilter) 688 return ERR_PTR(-ENOMEM); 689 690 mutex_init(&sfilter->notify_lock); 691 ret = bpf_prog_create_from_user(&sfilter->prog, fprog, 692 seccomp_check_filter, save_orig); 693 if (ret < 0) { 694 kfree(sfilter); 695 return ERR_PTR(ret); 696 } 697 698 refcount_set(&sfilter->refs, 1); 699 refcount_set(&sfilter->users, 1); 700 init_waitqueue_head(&sfilter->wqh); 701 702 return sfilter; 703 } 704 705 /** 706 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog 707 * @user_filter: pointer to the user data containing a sock_fprog. 708 * 709 * Returns 0 on success and non-zero otherwise. 710 */ 711 static struct seccomp_filter * 712 seccomp_prepare_user_filter(const char __user *user_filter) 713 { 714 struct sock_fprog fprog; 715 struct seccomp_filter *filter = ERR_PTR(-EFAULT); 716 717 #ifdef CONFIG_COMPAT 718 if (in_compat_syscall()) { 719 struct compat_sock_fprog fprog32; 720 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) 721 goto out; 722 fprog.len = fprog32.len; 723 fprog.filter = compat_ptr(fprog32.filter); 724 } else /* falls through to the if below. */ 725 #endif 726 if (copy_from_user(&fprog, user_filter, sizeof(fprog))) 727 goto out; 728 filter = seccomp_prepare_filter(&fprog); 729 out: 730 return filter; 731 } 732 733 #ifdef SECCOMP_ARCH_NATIVE 734 /** 735 * seccomp_is_const_allow - check if filter is constant allow with given data 736 * @fprog: The BPF programs 737 * @sd: The seccomp data to check against, only syscall number and arch 738 * number are considered constant. 739 */ 740 static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog, 741 struct seccomp_data *sd) 742 { 743 unsigned int reg_value = 0; 744 unsigned int pc; 745 bool op_res; 746 747 if (WARN_ON_ONCE(!fprog)) 748 return false; 749 750 /* Our single exception to filtering. */ 751 #ifdef __NR_uretprobe 752 #ifdef SECCOMP_ARCH_COMPAT 753 if (sd->arch == SECCOMP_ARCH_NATIVE) 754 #endif 755 if (sd->nr == __NR_uretprobe) 756 return true; 757 #endif 758 759 for (pc = 0; pc < fprog->len; pc++) { 760 struct sock_filter *insn = &fprog->filter[pc]; 761 u16 code = insn->code; 762 u32 k = insn->k; 763 764 switch (code) { 765 case BPF_LD | BPF_W | BPF_ABS: 766 switch (k) { 767 case offsetof(struct seccomp_data, nr): 768 reg_value = sd->nr; 769 break; 770 case offsetof(struct seccomp_data, arch): 771 reg_value = sd->arch; 772 break; 773 default: 774 /* can't optimize (non-constant value load) */ 775 return false; 776 } 777 break; 778 case BPF_RET | BPF_K: 779 /* reached return with constant values only, check allow */ 780 return k == SECCOMP_RET_ALLOW; 781 case BPF_JMP | BPF_JA: 782 pc += insn->k; 783 break; 784 case BPF_JMP | BPF_JEQ | BPF_K: 785 case BPF_JMP | BPF_JGE | BPF_K: 786 case BPF_JMP | BPF_JGT | BPF_K: 787 case BPF_JMP | BPF_JSET | BPF_K: 788 switch (BPF_OP(code)) { 789 case BPF_JEQ: 790 op_res = reg_value == k; 791 break; 792 case BPF_JGE: 793 op_res = reg_value >= k; 794 break; 795 case BPF_JGT: 796 op_res = reg_value > k; 797 break; 798 case BPF_JSET: 799 op_res = !!(reg_value & k); 800 break; 801 default: 802 /* can't optimize (unknown jump) */ 803 return false; 804 } 805 806 pc += op_res ? insn->jt : insn->jf; 807 break; 808 case BPF_ALU | BPF_AND | BPF_K: 809 reg_value &= k; 810 break; 811 default: 812 /* can't optimize (unknown insn) */ 813 return false; 814 } 815 } 816 817 /* ran off the end of the filter?! */ 818 WARN_ON(1); 819 return false; 820 } 821 822 static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter, 823 void *bitmap, const void *bitmap_prev, 824 size_t bitmap_size, int arch) 825 { 826 struct sock_fprog_kern *fprog = sfilter->prog->orig_prog; 827 struct seccomp_data sd; 828 int nr; 829 830 if (bitmap_prev) { 831 /* The new filter must be as restrictive as the last. */ 832 bitmap_copy(bitmap, bitmap_prev, bitmap_size); 833 } else { 834 /* Before any filters, all syscalls are always allowed. */ 835 bitmap_fill(bitmap, bitmap_size); 836 } 837 838 for (nr = 0; nr < bitmap_size; nr++) { 839 /* No bitmap change: not a cacheable action. */ 840 if (!test_bit(nr, bitmap)) 841 continue; 842 843 sd.nr = nr; 844 sd.arch = arch; 845 846 /* No bitmap change: continue to always allow. */ 847 if (seccomp_is_const_allow(fprog, &sd)) 848 continue; 849 850 /* 851 * Not a cacheable action: always run filters. 852 * atomic clear_bit() not needed, filter not visible yet. 853 */ 854 __clear_bit(nr, bitmap); 855 } 856 } 857 858 /** 859 * seccomp_cache_prepare - emulate the filter to find cacheable syscalls 860 * @sfilter: The seccomp filter 861 * 862 * Returns 0 if successful or -errno if error occurred. 863 */ 864 static void seccomp_cache_prepare(struct seccomp_filter *sfilter) 865 { 866 struct action_cache *cache = &sfilter->cache; 867 const struct action_cache *cache_prev = 868 sfilter->prev ? &sfilter->prev->cache : NULL; 869 870 seccomp_cache_prepare_bitmap(sfilter, cache->allow_native, 871 cache_prev ? cache_prev->allow_native : NULL, 872 SECCOMP_ARCH_NATIVE_NR, 873 SECCOMP_ARCH_NATIVE); 874 875 #ifdef SECCOMP_ARCH_COMPAT 876 seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat, 877 cache_prev ? cache_prev->allow_compat : NULL, 878 SECCOMP_ARCH_COMPAT_NR, 879 SECCOMP_ARCH_COMPAT); 880 #endif /* SECCOMP_ARCH_COMPAT */ 881 } 882 #endif /* SECCOMP_ARCH_NATIVE */ 883 884 /** 885 * seccomp_attach_filter: validate and attach filter 886 * @flags: flags to change filter behavior 887 * @filter: seccomp filter to add to the current process 888 * 889 * Caller must be holding current->sighand->siglock lock. 890 * 891 * Returns 0 on success, -ve on error, or 892 * - in TSYNC mode: the pid of a thread which was either not in the correct 893 * seccomp mode or did not have an ancestral seccomp filter 894 * - in NEW_LISTENER mode: the fd of the new listener 895 */ 896 static long seccomp_attach_filter(unsigned int flags, 897 struct seccomp_filter *filter) 898 { 899 unsigned long total_insns; 900 struct seccomp_filter *walker; 901 902 assert_spin_locked(¤t->sighand->siglock); 903 904 /* Validate resulting filter length. */ 905 total_insns = filter->prog->len; 906 for (walker = current->seccomp.filter; walker; walker = walker->prev) 907 total_insns += walker->prog->len + 4; /* 4 instr penalty */ 908 if (total_insns > MAX_INSNS_PER_PATH) 909 return -ENOMEM; 910 911 /* If thread sync has been requested, check that it is possible. */ 912 if (flags & SECCOMP_FILTER_FLAG_TSYNC) { 913 int ret; 914 915 ret = seccomp_can_sync_threads(); 916 if (ret) { 917 if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) 918 return -ESRCH; 919 else 920 return ret; 921 } 922 } 923 924 /* Set log flag, if present. */ 925 if (flags & SECCOMP_FILTER_FLAG_LOG) 926 filter->log = true; 927 928 /* Set wait killable flag, if present. */ 929 if (flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) 930 filter->wait_killable_recv = true; 931 932 /* 933 * If there is an existing filter, make it the prev and don't drop its 934 * task reference. 935 */ 936 filter->prev = current->seccomp.filter; 937 seccomp_cache_prepare(filter); 938 current->seccomp.filter = filter; 939 atomic_inc(¤t->seccomp.filter_count); 940 941 /* Now that the new filter is in place, synchronize to all threads. */ 942 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 943 seccomp_sync_threads(flags); 944 945 return 0; 946 } 947 948 static void __get_seccomp_filter(struct seccomp_filter *filter) 949 { 950 refcount_inc(&filter->refs); 951 } 952 953 /* get_seccomp_filter - increments the reference count of the filter on @tsk */ 954 void get_seccomp_filter(struct task_struct *tsk) 955 { 956 struct seccomp_filter *orig = tsk->seccomp.filter; 957 if (!orig) 958 return; 959 __get_seccomp_filter(orig); 960 refcount_inc(&orig->users); 961 } 962 963 #endif /* CONFIG_SECCOMP_FILTER */ 964 965 /* For use with seccomp_actions_logged */ 966 #define SECCOMP_LOG_KILL_PROCESS (1 << 0) 967 #define SECCOMP_LOG_KILL_THREAD (1 << 1) 968 #define SECCOMP_LOG_TRAP (1 << 2) 969 #define SECCOMP_LOG_ERRNO (1 << 3) 970 #define SECCOMP_LOG_TRACE (1 << 4) 971 #define SECCOMP_LOG_LOG (1 << 5) 972 #define SECCOMP_LOG_ALLOW (1 << 6) 973 #define SECCOMP_LOG_USER_NOTIF (1 << 7) 974 975 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | 976 SECCOMP_LOG_KILL_THREAD | 977 SECCOMP_LOG_TRAP | 978 SECCOMP_LOG_ERRNO | 979 SECCOMP_LOG_USER_NOTIF | 980 SECCOMP_LOG_TRACE | 981 SECCOMP_LOG_LOG; 982 983 static inline void seccomp_log(unsigned long syscall, long signr, u32 action, 984 bool requested) 985 { 986 bool log = false; 987 988 switch (action) { 989 case SECCOMP_RET_ALLOW: 990 break; 991 case SECCOMP_RET_TRAP: 992 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; 993 break; 994 case SECCOMP_RET_ERRNO: 995 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; 996 break; 997 case SECCOMP_RET_TRACE: 998 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; 999 break; 1000 case SECCOMP_RET_USER_NOTIF: 1001 log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF; 1002 break; 1003 case SECCOMP_RET_LOG: 1004 log = seccomp_actions_logged & SECCOMP_LOG_LOG; 1005 break; 1006 case SECCOMP_RET_KILL_THREAD: 1007 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; 1008 break; 1009 case SECCOMP_RET_KILL_PROCESS: 1010 default: 1011 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; 1012 } 1013 1014 /* 1015 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the 1016 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence 1017 * any action from being logged by removing the action name from the 1018 * seccomp_actions_logged sysctl. 1019 */ 1020 if (!log) 1021 return; 1022 1023 audit_seccomp(syscall, signr, action); 1024 } 1025 1026 /* 1027 * Secure computing mode 1 allows only read/write/exit/sigreturn. 1028 * To be fully secure this must be combined with rlimit 1029 * to limit the stack allocations too. 1030 */ 1031 static const int mode1_syscalls[] = { 1032 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, 1033 #ifdef __NR_uretprobe 1034 __NR_uretprobe, 1035 #endif 1036 -1, /* negative terminated */ 1037 }; 1038 1039 static void __secure_computing_strict(int this_syscall) 1040 { 1041 const int *allowed_syscalls = mode1_syscalls; 1042 #ifdef CONFIG_COMPAT 1043 if (in_compat_syscall()) 1044 allowed_syscalls = get_compat_mode1_syscalls(); 1045 #endif 1046 do { 1047 if (*allowed_syscalls == this_syscall) 1048 return; 1049 } while (*++allowed_syscalls != -1); 1050 1051 #ifdef SECCOMP_DEBUG 1052 dump_stack(); 1053 #endif 1054 current->seccomp.mode = SECCOMP_MODE_DEAD; 1055 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); 1056 do_exit(SIGKILL); 1057 } 1058 1059 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER 1060 void secure_computing_strict(int this_syscall) 1061 { 1062 int mode = current->seccomp.mode; 1063 1064 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 1065 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 1066 return; 1067 1068 if (mode == SECCOMP_MODE_DISABLED) 1069 return; 1070 else if (mode == SECCOMP_MODE_STRICT) 1071 __secure_computing_strict(this_syscall); 1072 else 1073 BUG(); 1074 } 1075 int __secure_computing(void) 1076 { 1077 int this_syscall = syscall_get_nr(current, current_pt_regs()); 1078 1079 secure_computing_strict(this_syscall); 1080 return 0; 1081 } 1082 #else 1083 1084 #ifdef CONFIG_SECCOMP_FILTER 1085 static u64 seccomp_next_notify_id(struct seccomp_filter *filter) 1086 { 1087 /* 1088 * Note: overflow is ok here, the id just needs to be unique per 1089 * filter. 1090 */ 1091 lockdep_assert_held(&filter->notify_lock); 1092 return filter->notif->next_id++; 1093 } 1094 1095 static void seccomp_handle_addfd(struct seccomp_kaddfd *addfd, struct seccomp_knotif *n) 1096 { 1097 int fd; 1098 1099 /* 1100 * Remove the notification, and reset the list pointers, indicating 1101 * that it has been handled. 1102 */ 1103 list_del_init(&addfd->list); 1104 if (!addfd->setfd) 1105 fd = receive_fd(addfd->file, NULL, addfd->flags); 1106 else 1107 fd = receive_fd_replace(addfd->fd, addfd->file, addfd->flags); 1108 addfd->ret = fd; 1109 1110 if (addfd->ioctl_flags & SECCOMP_ADDFD_FLAG_SEND) { 1111 /* If we fail reset and return an error to the notifier */ 1112 if (fd < 0) { 1113 n->state = SECCOMP_NOTIFY_SENT; 1114 } else { 1115 /* Return the FD we just added */ 1116 n->flags = 0; 1117 n->error = 0; 1118 n->val = fd; 1119 } 1120 } 1121 1122 /* 1123 * Mark the notification as completed. From this point, addfd mem 1124 * might be invalidated and we can't safely read it anymore. 1125 */ 1126 complete(&addfd->completion); 1127 } 1128 1129 static bool should_sleep_killable(struct seccomp_filter *match, 1130 struct seccomp_knotif *n) 1131 { 1132 return match->wait_killable_recv && n->state == SECCOMP_NOTIFY_SENT; 1133 } 1134 1135 static int seccomp_do_user_notification(int this_syscall, 1136 struct seccomp_filter *match, 1137 const struct seccomp_data *sd) 1138 { 1139 int err; 1140 u32 flags = 0; 1141 long ret = 0; 1142 struct seccomp_knotif n = {}; 1143 struct seccomp_kaddfd *addfd, *tmp; 1144 1145 mutex_lock(&match->notify_lock); 1146 err = -ENOSYS; 1147 if (!match->notif) 1148 goto out; 1149 1150 n.task = current; 1151 n.state = SECCOMP_NOTIFY_INIT; 1152 n.data = sd; 1153 n.id = seccomp_next_notify_id(match); 1154 init_completion(&n.ready); 1155 list_add_tail(&n.list, &match->notif->notifications); 1156 INIT_LIST_HEAD(&n.addfd); 1157 1158 atomic_inc(&match->notif->requests); 1159 if (match->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) 1160 wake_up_poll_on_current_cpu(&match->wqh, EPOLLIN | EPOLLRDNORM); 1161 else 1162 wake_up_poll(&match->wqh, EPOLLIN | EPOLLRDNORM); 1163 1164 /* 1165 * This is where we wait for a reply from userspace. 1166 */ 1167 do { 1168 bool wait_killable = should_sleep_killable(match, &n); 1169 1170 mutex_unlock(&match->notify_lock); 1171 if (wait_killable) 1172 err = wait_for_completion_killable(&n.ready); 1173 else 1174 err = wait_for_completion_interruptible(&n.ready); 1175 mutex_lock(&match->notify_lock); 1176 1177 if (err != 0) { 1178 /* 1179 * Check to see if the notifcation got picked up and 1180 * whether we should switch to wait killable. 1181 */ 1182 if (!wait_killable && should_sleep_killable(match, &n)) 1183 continue; 1184 1185 goto interrupted; 1186 } 1187 1188 addfd = list_first_entry_or_null(&n.addfd, 1189 struct seccomp_kaddfd, list); 1190 /* Check if we were woken up by a addfd message */ 1191 if (addfd) 1192 seccomp_handle_addfd(addfd, &n); 1193 1194 } while (n.state != SECCOMP_NOTIFY_REPLIED); 1195 1196 ret = n.val; 1197 err = n.error; 1198 flags = n.flags; 1199 1200 interrupted: 1201 /* If there were any pending addfd calls, clear them out */ 1202 list_for_each_entry_safe(addfd, tmp, &n.addfd, list) { 1203 /* The process went away before we got a chance to handle it */ 1204 addfd->ret = -ESRCH; 1205 list_del_init(&addfd->list); 1206 complete(&addfd->completion); 1207 } 1208 1209 /* 1210 * Note that it's possible the listener died in between the time when 1211 * we were notified of a response (or a signal) and when we were able to 1212 * re-acquire the lock, so only delete from the list if the 1213 * notification actually exists. 1214 * 1215 * Also note that this test is only valid because there's no way to 1216 * *reattach* to a notifier right now. If one is added, we'll need to 1217 * keep track of the notif itself and make sure they match here. 1218 */ 1219 if (match->notif) 1220 list_del(&n.list); 1221 out: 1222 mutex_unlock(&match->notify_lock); 1223 1224 /* Userspace requests to continue the syscall. */ 1225 if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) 1226 return 0; 1227 1228 syscall_set_return_value(current, current_pt_regs(), 1229 err, ret); 1230 return -1; 1231 } 1232 1233 static int __seccomp_filter(int this_syscall, const bool recheck_after_trace) 1234 { 1235 u32 filter_ret, action; 1236 struct seccomp_data sd; 1237 struct seccomp_filter *match = NULL; 1238 int data; 1239 1240 /* 1241 * Make sure that any changes to mode from another thread have 1242 * been seen after SYSCALL_WORK_SECCOMP was seen. 1243 */ 1244 smp_rmb(); 1245 1246 populate_seccomp_data(&sd); 1247 1248 filter_ret = seccomp_run_filters(&sd, &match); 1249 data = filter_ret & SECCOMP_RET_DATA; 1250 action = filter_ret & SECCOMP_RET_ACTION_FULL; 1251 1252 switch (action) { 1253 case SECCOMP_RET_ERRNO: 1254 /* Set low-order bits as an errno, capped at MAX_ERRNO. */ 1255 if (data > MAX_ERRNO) 1256 data = MAX_ERRNO; 1257 syscall_set_return_value(current, current_pt_regs(), 1258 -data, 0); 1259 goto skip; 1260 1261 case SECCOMP_RET_TRAP: 1262 /* Show the handler the original registers. */ 1263 syscall_rollback(current, current_pt_regs()); 1264 /* Let the filter pass back 16 bits of data. */ 1265 force_sig_seccomp(this_syscall, data, false); 1266 goto skip; 1267 1268 case SECCOMP_RET_TRACE: 1269 /* We've been put in this state by the ptracer already. */ 1270 if (recheck_after_trace) 1271 return 0; 1272 1273 /* ENOSYS these calls if there is no tracer attached. */ 1274 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { 1275 syscall_set_return_value(current, 1276 current_pt_regs(), 1277 -ENOSYS, 0); 1278 goto skip; 1279 } 1280 1281 /* Allow the BPF to provide the event message */ 1282 ptrace_event(PTRACE_EVENT_SECCOMP, data); 1283 /* 1284 * The delivery of a fatal signal during event 1285 * notification may silently skip tracer notification, 1286 * which could leave us with a potentially unmodified 1287 * syscall that the tracer would have liked to have 1288 * changed. Since the process is about to die, we just 1289 * force the syscall to be skipped and let the signal 1290 * kill the process and correctly handle any tracer exit 1291 * notifications. 1292 */ 1293 if (fatal_signal_pending(current)) 1294 goto skip; 1295 /* Check if the tracer forced the syscall to be skipped. */ 1296 this_syscall = syscall_get_nr(current, current_pt_regs()); 1297 if (this_syscall < 0) 1298 goto skip; 1299 1300 /* 1301 * Recheck the syscall, since it may have changed. This 1302 * intentionally uses a NULL struct seccomp_data to force 1303 * a reload of all registers. This does not goto skip since 1304 * a skip would have already been reported. 1305 */ 1306 if (__seccomp_filter(this_syscall, true)) 1307 return -1; 1308 1309 return 0; 1310 1311 case SECCOMP_RET_USER_NOTIF: 1312 if (seccomp_do_user_notification(this_syscall, match, &sd)) 1313 goto skip; 1314 1315 return 0; 1316 1317 case SECCOMP_RET_LOG: 1318 seccomp_log(this_syscall, 0, action, true); 1319 return 0; 1320 1321 case SECCOMP_RET_ALLOW: 1322 /* 1323 * Note that the "match" filter will always be NULL for 1324 * this action since SECCOMP_RET_ALLOW is the starting 1325 * state in seccomp_run_filters(). 1326 */ 1327 return 0; 1328 1329 case SECCOMP_RET_KILL_THREAD: 1330 case SECCOMP_RET_KILL_PROCESS: 1331 default: 1332 current->seccomp.mode = SECCOMP_MODE_DEAD; 1333 seccomp_log(this_syscall, SIGSYS, action, true); 1334 /* Dump core only if this is the last remaining thread. */ 1335 if (action != SECCOMP_RET_KILL_THREAD || 1336 (atomic_read(¤t->signal->live) == 1)) { 1337 /* Show the original registers in the dump. */ 1338 syscall_rollback(current, current_pt_regs()); 1339 /* Trigger a coredump with SIGSYS */ 1340 force_sig_seccomp(this_syscall, data, true); 1341 } else { 1342 do_exit(SIGSYS); 1343 } 1344 return -1; /* skip the syscall go directly to signal handling */ 1345 } 1346 1347 unreachable(); 1348 1349 skip: 1350 seccomp_log(this_syscall, 0, action, match ? match->log : false); 1351 return -1; 1352 } 1353 #else 1354 static int __seccomp_filter(int this_syscall, const bool recheck_after_trace) 1355 { 1356 BUG(); 1357 1358 return -1; 1359 } 1360 #endif 1361 1362 int __secure_computing(void) 1363 { 1364 int mode = current->seccomp.mode; 1365 int this_syscall; 1366 1367 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 1368 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 1369 return 0; 1370 1371 this_syscall = syscall_get_nr(current, current_pt_regs()); 1372 1373 switch (mode) { 1374 case SECCOMP_MODE_STRICT: 1375 __secure_computing_strict(this_syscall); /* may call do_exit */ 1376 return 0; 1377 case SECCOMP_MODE_FILTER: 1378 return __seccomp_filter(this_syscall, false); 1379 /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */ 1380 case SECCOMP_MODE_DEAD: 1381 WARN_ON_ONCE(1); 1382 do_exit(SIGKILL); 1383 return -1; 1384 default: 1385 BUG(); 1386 } 1387 } 1388 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ 1389 1390 long prctl_get_seccomp(void) 1391 { 1392 return current->seccomp.mode; 1393 } 1394 1395 /** 1396 * seccomp_set_mode_strict: internal function for setting strict seccomp 1397 * 1398 * Once current->seccomp.mode is non-zero, it may not be changed. 1399 * 1400 * Returns 0 on success or -EINVAL on failure. 1401 */ 1402 static long seccomp_set_mode_strict(void) 1403 { 1404 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; 1405 long ret = -EINVAL; 1406 1407 spin_lock_irq(¤t->sighand->siglock); 1408 1409 if (!seccomp_may_assign_mode(seccomp_mode)) 1410 goto out; 1411 1412 #ifdef TIF_NOTSC 1413 disable_TSC(); 1414 #endif 1415 seccomp_assign_mode(current, seccomp_mode, 0); 1416 ret = 0; 1417 1418 out: 1419 spin_unlock_irq(¤t->sighand->siglock); 1420 1421 return ret; 1422 } 1423 1424 #ifdef CONFIG_SECCOMP_FILTER 1425 static void seccomp_notify_free(struct seccomp_filter *filter) 1426 { 1427 kfree(filter->notif); 1428 filter->notif = NULL; 1429 } 1430 1431 static void seccomp_notify_detach(struct seccomp_filter *filter) 1432 { 1433 struct seccomp_knotif *knotif; 1434 1435 if (!filter) 1436 return; 1437 1438 mutex_lock(&filter->notify_lock); 1439 1440 /* 1441 * If this file is being closed because e.g. the task who owned it 1442 * died, let's wake everyone up who was waiting on us. 1443 */ 1444 list_for_each_entry(knotif, &filter->notif->notifications, list) { 1445 if (knotif->state == SECCOMP_NOTIFY_REPLIED) 1446 continue; 1447 1448 knotif->state = SECCOMP_NOTIFY_REPLIED; 1449 knotif->error = -ENOSYS; 1450 knotif->val = 0; 1451 1452 /* 1453 * We do not need to wake up any pending addfd messages, as 1454 * the notifier will do that for us, as this just looks 1455 * like a standard reply. 1456 */ 1457 complete(&knotif->ready); 1458 } 1459 1460 seccomp_notify_free(filter); 1461 mutex_unlock(&filter->notify_lock); 1462 } 1463 1464 static int seccomp_notify_release(struct inode *inode, struct file *file) 1465 { 1466 struct seccomp_filter *filter = file->private_data; 1467 1468 seccomp_notify_detach(filter); 1469 __put_seccomp_filter(filter); 1470 return 0; 1471 } 1472 1473 /* must be called with notif_lock held */ 1474 static inline struct seccomp_knotif * 1475 find_notification(struct seccomp_filter *filter, u64 id) 1476 { 1477 struct seccomp_knotif *cur; 1478 1479 lockdep_assert_held(&filter->notify_lock); 1480 1481 list_for_each_entry(cur, &filter->notif->notifications, list) { 1482 if (cur->id == id) 1483 return cur; 1484 } 1485 1486 return NULL; 1487 } 1488 1489 static int recv_wake_function(wait_queue_entry_t *wait, unsigned int mode, int sync, 1490 void *key) 1491 { 1492 /* Avoid a wakeup if event not interesting for us. */ 1493 if (key && !(key_to_poll(key) & (EPOLLIN | EPOLLERR | EPOLLHUP))) 1494 return 0; 1495 return autoremove_wake_function(wait, mode, sync, key); 1496 } 1497 1498 static int recv_wait_event(struct seccomp_filter *filter) 1499 { 1500 DEFINE_WAIT_FUNC(wait, recv_wake_function); 1501 int ret; 1502 1503 if (refcount_read(&filter->users) == 0) 1504 return 0; 1505 1506 if (atomic_dec_if_positive(&filter->notif->requests) >= 0) 1507 return 0; 1508 1509 for (;;) { 1510 ret = prepare_to_wait_event(&filter->wqh, &wait, TASK_INTERRUPTIBLE); 1511 1512 if (atomic_dec_if_positive(&filter->notif->requests) >= 0) 1513 break; 1514 if (refcount_read(&filter->users) == 0) 1515 break; 1516 1517 if (ret) 1518 return ret; 1519 1520 schedule(); 1521 } 1522 finish_wait(&filter->wqh, &wait); 1523 return 0; 1524 } 1525 1526 static long seccomp_notify_recv(struct seccomp_filter *filter, 1527 void __user *buf) 1528 { 1529 struct seccomp_knotif *knotif = NULL, *cur; 1530 struct seccomp_notif unotif; 1531 ssize_t ret; 1532 1533 /* Verify that we're not given garbage to keep struct extensible. */ 1534 ret = check_zeroed_user(buf, sizeof(unotif)); 1535 if (ret < 0) 1536 return ret; 1537 if (!ret) 1538 return -EINVAL; 1539 1540 memset(&unotif, 0, sizeof(unotif)); 1541 1542 ret = recv_wait_event(filter); 1543 if (ret < 0) 1544 return ret; 1545 1546 mutex_lock(&filter->notify_lock); 1547 list_for_each_entry(cur, &filter->notif->notifications, list) { 1548 if (cur->state == SECCOMP_NOTIFY_INIT) { 1549 knotif = cur; 1550 break; 1551 } 1552 } 1553 1554 /* 1555 * If we didn't find a notification, it could be that the task was 1556 * interrupted by a fatal signal between the time we were woken and 1557 * when we were able to acquire the rw lock. 1558 */ 1559 if (!knotif) { 1560 ret = -ENOENT; 1561 goto out; 1562 } 1563 1564 unotif.id = knotif->id; 1565 unotif.pid = task_pid_vnr(knotif->task); 1566 unotif.data = *(knotif->data); 1567 1568 knotif->state = SECCOMP_NOTIFY_SENT; 1569 wake_up_poll(&filter->wqh, EPOLLOUT | EPOLLWRNORM); 1570 ret = 0; 1571 out: 1572 mutex_unlock(&filter->notify_lock); 1573 1574 if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) { 1575 ret = -EFAULT; 1576 1577 /* 1578 * Userspace screwed up. To make sure that we keep this 1579 * notification alive, let's reset it back to INIT. It 1580 * may have died when we released the lock, so we need to make 1581 * sure it's still around. 1582 */ 1583 mutex_lock(&filter->notify_lock); 1584 knotif = find_notification(filter, unotif.id); 1585 if (knotif) { 1586 /* Reset the process to make sure it's not stuck */ 1587 if (should_sleep_killable(filter, knotif)) 1588 complete(&knotif->ready); 1589 knotif->state = SECCOMP_NOTIFY_INIT; 1590 atomic_inc(&filter->notif->requests); 1591 wake_up_poll(&filter->wqh, EPOLLIN | EPOLLRDNORM); 1592 } 1593 mutex_unlock(&filter->notify_lock); 1594 } 1595 1596 return ret; 1597 } 1598 1599 static long seccomp_notify_send(struct seccomp_filter *filter, 1600 void __user *buf) 1601 { 1602 struct seccomp_notif_resp resp = {}; 1603 struct seccomp_knotif *knotif; 1604 long ret; 1605 1606 if (copy_from_user(&resp, buf, sizeof(resp))) 1607 return -EFAULT; 1608 1609 if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE) 1610 return -EINVAL; 1611 1612 if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) && 1613 (resp.error || resp.val)) 1614 return -EINVAL; 1615 1616 ret = mutex_lock_interruptible(&filter->notify_lock); 1617 if (ret < 0) 1618 return ret; 1619 1620 knotif = find_notification(filter, resp.id); 1621 if (!knotif) { 1622 ret = -ENOENT; 1623 goto out; 1624 } 1625 1626 /* Allow exactly one reply. */ 1627 if (knotif->state != SECCOMP_NOTIFY_SENT) { 1628 ret = -EINPROGRESS; 1629 goto out; 1630 } 1631 1632 ret = 0; 1633 knotif->state = SECCOMP_NOTIFY_REPLIED; 1634 knotif->error = resp.error; 1635 knotif->val = resp.val; 1636 knotif->flags = resp.flags; 1637 if (filter->notif->flags & SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) 1638 complete_on_current_cpu(&knotif->ready); 1639 else 1640 complete(&knotif->ready); 1641 out: 1642 mutex_unlock(&filter->notify_lock); 1643 return ret; 1644 } 1645 1646 static long seccomp_notify_id_valid(struct seccomp_filter *filter, 1647 void __user *buf) 1648 { 1649 struct seccomp_knotif *knotif; 1650 u64 id; 1651 long ret; 1652 1653 if (copy_from_user(&id, buf, sizeof(id))) 1654 return -EFAULT; 1655 1656 ret = mutex_lock_interruptible(&filter->notify_lock); 1657 if (ret < 0) 1658 return ret; 1659 1660 knotif = find_notification(filter, id); 1661 if (knotif && knotif->state == SECCOMP_NOTIFY_SENT) 1662 ret = 0; 1663 else 1664 ret = -ENOENT; 1665 1666 mutex_unlock(&filter->notify_lock); 1667 return ret; 1668 } 1669 1670 static long seccomp_notify_set_flags(struct seccomp_filter *filter, 1671 unsigned long flags) 1672 { 1673 long ret; 1674 1675 if (flags & ~SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP) 1676 return -EINVAL; 1677 1678 ret = mutex_lock_interruptible(&filter->notify_lock); 1679 if (ret < 0) 1680 return ret; 1681 filter->notif->flags = flags; 1682 mutex_unlock(&filter->notify_lock); 1683 return 0; 1684 } 1685 1686 static long seccomp_notify_addfd(struct seccomp_filter *filter, 1687 struct seccomp_notif_addfd __user *uaddfd, 1688 unsigned int size) 1689 { 1690 struct seccomp_notif_addfd addfd; 1691 struct seccomp_knotif *knotif; 1692 struct seccomp_kaddfd kaddfd; 1693 int ret; 1694 1695 BUILD_BUG_ON(sizeof(addfd) < SECCOMP_NOTIFY_ADDFD_SIZE_VER0); 1696 BUILD_BUG_ON(sizeof(addfd) != SECCOMP_NOTIFY_ADDFD_SIZE_LATEST); 1697 1698 if (size < SECCOMP_NOTIFY_ADDFD_SIZE_VER0 || size >= PAGE_SIZE) 1699 return -EINVAL; 1700 1701 ret = copy_struct_from_user(&addfd, sizeof(addfd), uaddfd, size); 1702 if (ret) 1703 return ret; 1704 1705 if (addfd.newfd_flags & ~O_CLOEXEC) 1706 return -EINVAL; 1707 1708 if (addfd.flags & ~(SECCOMP_ADDFD_FLAG_SETFD | SECCOMP_ADDFD_FLAG_SEND)) 1709 return -EINVAL; 1710 1711 if (addfd.newfd && !(addfd.flags & SECCOMP_ADDFD_FLAG_SETFD)) 1712 return -EINVAL; 1713 1714 kaddfd.file = fget(addfd.srcfd); 1715 if (!kaddfd.file) 1716 return -EBADF; 1717 1718 kaddfd.ioctl_flags = addfd.flags; 1719 kaddfd.flags = addfd.newfd_flags; 1720 kaddfd.setfd = addfd.flags & SECCOMP_ADDFD_FLAG_SETFD; 1721 kaddfd.fd = addfd.newfd; 1722 init_completion(&kaddfd.completion); 1723 1724 ret = mutex_lock_interruptible(&filter->notify_lock); 1725 if (ret < 0) 1726 goto out; 1727 1728 knotif = find_notification(filter, addfd.id); 1729 if (!knotif) { 1730 ret = -ENOENT; 1731 goto out_unlock; 1732 } 1733 1734 /* 1735 * We do not want to allow for FD injection to occur before the 1736 * notification has been picked up by a userspace handler, or after 1737 * the notification has been replied to. 1738 */ 1739 if (knotif->state != SECCOMP_NOTIFY_SENT) { 1740 ret = -EINPROGRESS; 1741 goto out_unlock; 1742 } 1743 1744 if (addfd.flags & SECCOMP_ADDFD_FLAG_SEND) { 1745 /* 1746 * Disallow queuing an atomic addfd + send reply while there are 1747 * some addfd requests still to process. 1748 * 1749 * There is no clear reason to support it and allows us to keep 1750 * the loop on the other side straight-forward. 1751 */ 1752 if (!list_empty(&knotif->addfd)) { 1753 ret = -EBUSY; 1754 goto out_unlock; 1755 } 1756 1757 /* Allow exactly only one reply */ 1758 knotif->state = SECCOMP_NOTIFY_REPLIED; 1759 } 1760 1761 list_add(&kaddfd.list, &knotif->addfd); 1762 complete(&knotif->ready); 1763 mutex_unlock(&filter->notify_lock); 1764 1765 /* Now we wait for it to be processed or be interrupted */ 1766 ret = wait_for_completion_interruptible(&kaddfd.completion); 1767 if (ret == 0) { 1768 /* 1769 * We had a successful completion. The other side has already 1770 * removed us from the addfd queue, and 1771 * wait_for_completion_interruptible has a memory barrier upon 1772 * success that lets us read this value directly without 1773 * locking. 1774 */ 1775 ret = kaddfd.ret; 1776 goto out; 1777 } 1778 1779 mutex_lock(&filter->notify_lock); 1780 /* 1781 * Even though we were woken up by a signal and not a successful 1782 * completion, a completion may have happened in the mean time. 1783 * 1784 * We need to check again if the addfd request has been handled, 1785 * and if not, we will remove it from the queue. 1786 */ 1787 if (list_empty(&kaddfd.list)) 1788 ret = kaddfd.ret; 1789 else 1790 list_del(&kaddfd.list); 1791 1792 out_unlock: 1793 mutex_unlock(&filter->notify_lock); 1794 out: 1795 fput(kaddfd.file); 1796 1797 return ret; 1798 } 1799 1800 static long seccomp_notify_ioctl(struct file *file, unsigned int cmd, 1801 unsigned long arg) 1802 { 1803 struct seccomp_filter *filter = file->private_data; 1804 void __user *buf = (void __user *)arg; 1805 1806 /* Fixed-size ioctls */ 1807 switch (cmd) { 1808 case SECCOMP_IOCTL_NOTIF_RECV: 1809 return seccomp_notify_recv(filter, buf); 1810 case SECCOMP_IOCTL_NOTIF_SEND: 1811 return seccomp_notify_send(filter, buf); 1812 case SECCOMP_IOCTL_NOTIF_ID_VALID_WRONG_DIR: 1813 case SECCOMP_IOCTL_NOTIF_ID_VALID: 1814 return seccomp_notify_id_valid(filter, buf); 1815 case SECCOMP_IOCTL_NOTIF_SET_FLAGS: 1816 return seccomp_notify_set_flags(filter, arg); 1817 } 1818 1819 /* Extensible Argument ioctls */ 1820 #define EA_IOCTL(cmd) ((cmd) & ~(IOC_INOUT | IOCSIZE_MASK)) 1821 switch (EA_IOCTL(cmd)) { 1822 case EA_IOCTL(SECCOMP_IOCTL_NOTIF_ADDFD): 1823 return seccomp_notify_addfd(filter, buf, _IOC_SIZE(cmd)); 1824 default: 1825 return -EINVAL; 1826 } 1827 } 1828 1829 static __poll_t seccomp_notify_poll(struct file *file, 1830 struct poll_table_struct *poll_tab) 1831 { 1832 struct seccomp_filter *filter = file->private_data; 1833 __poll_t ret = 0; 1834 struct seccomp_knotif *cur; 1835 1836 poll_wait(file, &filter->wqh, poll_tab); 1837 1838 if (mutex_lock_interruptible(&filter->notify_lock) < 0) 1839 return EPOLLERR; 1840 1841 list_for_each_entry(cur, &filter->notif->notifications, list) { 1842 if (cur->state == SECCOMP_NOTIFY_INIT) 1843 ret |= EPOLLIN | EPOLLRDNORM; 1844 if (cur->state == SECCOMP_NOTIFY_SENT) 1845 ret |= EPOLLOUT | EPOLLWRNORM; 1846 if ((ret & EPOLLIN) && (ret & EPOLLOUT)) 1847 break; 1848 } 1849 1850 mutex_unlock(&filter->notify_lock); 1851 1852 if (refcount_read(&filter->users) == 0) 1853 ret |= EPOLLHUP; 1854 1855 return ret; 1856 } 1857 1858 static const struct file_operations seccomp_notify_ops = { 1859 .poll = seccomp_notify_poll, 1860 .release = seccomp_notify_release, 1861 .unlocked_ioctl = seccomp_notify_ioctl, 1862 .compat_ioctl = seccomp_notify_ioctl, 1863 }; 1864 1865 static struct file *init_listener(struct seccomp_filter *filter) 1866 { 1867 struct file *ret; 1868 1869 ret = ERR_PTR(-ENOMEM); 1870 filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); 1871 if (!filter->notif) 1872 goto out; 1873 1874 filter->notif->next_id = get_random_u64(); 1875 INIT_LIST_HEAD(&filter->notif->notifications); 1876 1877 ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, 1878 filter, O_RDWR); 1879 if (IS_ERR(ret)) 1880 goto out_notif; 1881 1882 /* The file has a reference to it now */ 1883 __get_seccomp_filter(filter); 1884 1885 out_notif: 1886 if (IS_ERR(ret)) 1887 seccomp_notify_free(filter); 1888 out: 1889 return ret; 1890 } 1891 1892 /* 1893 * Does @new_child have a listener while an ancestor also has a listener? 1894 * If so, we'll want to reject this filter. 1895 * This only has to be tested for the current process, even in the TSYNC case, 1896 * because TSYNC installs @child with the same parent on all threads. 1897 * Note that @new_child is not hooked up to its parent at this point yet, so 1898 * we use current->seccomp.filter. 1899 */ 1900 static bool has_duplicate_listener(struct seccomp_filter *new_child) 1901 { 1902 struct seccomp_filter *cur; 1903 1904 /* must be protected against concurrent TSYNC */ 1905 lockdep_assert_held(¤t->sighand->siglock); 1906 1907 if (!new_child->notif) 1908 return false; 1909 for (cur = current->seccomp.filter; cur; cur = cur->prev) { 1910 if (cur->notif) 1911 return true; 1912 } 1913 1914 return false; 1915 } 1916 1917 /** 1918 * seccomp_set_mode_filter: internal function for setting seccomp filter 1919 * @flags: flags to change filter behavior 1920 * @filter: struct sock_fprog containing filter 1921 * 1922 * This function may be called repeatedly to install additional filters. 1923 * Every filter successfully installed will be evaluated (in reverse order) 1924 * for each system call the task makes. 1925 * 1926 * Once current->seccomp.mode is non-zero, it may not be changed. 1927 * 1928 * Returns 0 on success or -EINVAL on failure. 1929 */ 1930 static long seccomp_set_mode_filter(unsigned int flags, 1931 const char __user *filter) 1932 { 1933 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; 1934 struct seccomp_filter *prepared = NULL; 1935 long ret = -EINVAL; 1936 int listener = -1; 1937 struct file *listener_f = NULL; 1938 1939 /* Validate flags. */ 1940 if (flags & ~SECCOMP_FILTER_FLAG_MASK) 1941 return -EINVAL; 1942 1943 /* 1944 * In the successful case, NEW_LISTENER returns the new listener fd. 1945 * But in the failure case, TSYNC returns the thread that died. If you 1946 * combine these two flags, there's no way to tell whether something 1947 * succeeded or failed. So, let's disallow this combination if the user 1948 * has not explicitly requested no errors from TSYNC. 1949 */ 1950 if ((flags & SECCOMP_FILTER_FLAG_TSYNC) && 1951 (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) && 1952 ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0)) 1953 return -EINVAL; 1954 1955 /* 1956 * The SECCOMP_FILTER_FLAG_WAIT_KILLABLE_SENT flag doesn't make sense 1957 * without the SECCOMP_FILTER_FLAG_NEW_LISTENER flag. 1958 */ 1959 if ((flags & SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) && 1960 ((flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) == 0)) 1961 return -EINVAL; 1962 1963 /* Prepare the new filter before holding any locks. */ 1964 prepared = seccomp_prepare_user_filter(filter); 1965 if (IS_ERR(prepared)) 1966 return PTR_ERR(prepared); 1967 1968 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 1969 listener = get_unused_fd_flags(O_CLOEXEC); 1970 if (listener < 0) { 1971 ret = listener; 1972 goto out_free; 1973 } 1974 1975 listener_f = init_listener(prepared); 1976 if (IS_ERR(listener_f)) { 1977 put_unused_fd(listener); 1978 ret = PTR_ERR(listener_f); 1979 goto out_free; 1980 } 1981 } 1982 1983 /* 1984 * Make sure we cannot change seccomp or nnp state via TSYNC 1985 * while another thread is in the middle of calling exec. 1986 */ 1987 if (flags & SECCOMP_FILTER_FLAG_TSYNC && 1988 mutex_lock_killable(¤t->signal->cred_guard_mutex)) 1989 goto out_put_fd; 1990 1991 spin_lock_irq(¤t->sighand->siglock); 1992 1993 if (!seccomp_may_assign_mode(seccomp_mode)) 1994 goto out; 1995 1996 if (has_duplicate_listener(prepared)) { 1997 ret = -EBUSY; 1998 goto out; 1999 } 2000 2001 ret = seccomp_attach_filter(flags, prepared); 2002 if (ret) 2003 goto out; 2004 /* Do not free the successfully attached filter. */ 2005 prepared = NULL; 2006 2007 seccomp_assign_mode(current, seccomp_mode, flags); 2008 out: 2009 spin_unlock_irq(¤t->sighand->siglock); 2010 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 2011 mutex_unlock(¤t->signal->cred_guard_mutex); 2012 out_put_fd: 2013 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 2014 if (ret) { 2015 listener_f->private_data = NULL; 2016 fput(listener_f); 2017 put_unused_fd(listener); 2018 seccomp_notify_detach(prepared); 2019 } else { 2020 fd_install(listener, listener_f); 2021 ret = listener; 2022 } 2023 } 2024 out_free: 2025 seccomp_filter_free(prepared); 2026 return ret; 2027 } 2028 #else 2029 static inline long seccomp_set_mode_filter(unsigned int flags, 2030 const char __user *filter) 2031 { 2032 return -EINVAL; 2033 } 2034 #endif 2035 2036 static long seccomp_get_action_avail(const char __user *uaction) 2037 { 2038 u32 action; 2039 2040 if (copy_from_user(&action, uaction, sizeof(action))) 2041 return -EFAULT; 2042 2043 switch (action) { 2044 case SECCOMP_RET_KILL_PROCESS: 2045 case SECCOMP_RET_KILL_THREAD: 2046 case SECCOMP_RET_TRAP: 2047 case SECCOMP_RET_ERRNO: 2048 case SECCOMP_RET_USER_NOTIF: 2049 case SECCOMP_RET_TRACE: 2050 case SECCOMP_RET_LOG: 2051 case SECCOMP_RET_ALLOW: 2052 break; 2053 default: 2054 return -EOPNOTSUPP; 2055 } 2056 2057 return 0; 2058 } 2059 2060 static long seccomp_get_notif_sizes(void __user *usizes) 2061 { 2062 struct seccomp_notif_sizes sizes = { 2063 .seccomp_notif = sizeof(struct seccomp_notif), 2064 .seccomp_notif_resp = sizeof(struct seccomp_notif_resp), 2065 .seccomp_data = sizeof(struct seccomp_data), 2066 }; 2067 2068 if (copy_to_user(usizes, &sizes, sizeof(sizes))) 2069 return -EFAULT; 2070 2071 return 0; 2072 } 2073 2074 /* Common entry point for both prctl and syscall. */ 2075 static long do_seccomp(unsigned int op, unsigned int flags, 2076 void __user *uargs) 2077 { 2078 switch (op) { 2079 case SECCOMP_SET_MODE_STRICT: 2080 if (flags != 0 || uargs != NULL) 2081 return -EINVAL; 2082 return seccomp_set_mode_strict(); 2083 case SECCOMP_SET_MODE_FILTER: 2084 return seccomp_set_mode_filter(flags, uargs); 2085 case SECCOMP_GET_ACTION_AVAIL: 2086 if (flags != 0) 2087 return -EINVAL; 2088 2089 return seccomp_get_action_avail(uargs); 2090 case SECCOMP_GET_NOTIF_SIZES: 2091 if (flags != 0) 2092 return -EINVAL; 2093 2094 return seccomp_get_notif_sizes(uargs); 2095 default: 2096 return -EINVAL; 2097 } 2098 } 2099 2100 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, 2101 void __user *, uargs) 2102 { 2103 return do_seccomp(op, flags, uargs); 2104 } 2105 2106 /** 2107 * prctl_set_seccomp: configures current->seccomp.mode 2108 * @seccomp_mode: requested mode to use 2109 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER 2110 * 2111 * Returns 0 on success or -EINVAL on failure. 2112 */ 2113 long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter) 2114 { 2115 unsigned int op; 2116 void __user *uargs; 2117 2118 switch (seccomp_mode) { 2119 case SECCOMP_MODE_STRICT: 2120 op = SECCOMP_SET_MODE_STRICT; 2121 /* 2122 * Setting strict mode through prctl always ignored filter, 2123 * so make sure it is always NULL here to pass the internal 2124 * check in do_seccomp(). 2125 */ 2126 uargs = NULL; 2127 break; 2128 case SECCOMP_MODE_FILTER: 2129 op = SECCOMP_SET_MODE_FILTER; 2130 uargs = filter; 2131 break; 2132 default: 2133 return -EINVAL; 2134 } 2135 2136 /* prctl interface doesn't have flags, so they are always zero. */ 2137 return do_seccomp(op, 0, uargs); 2138 } 2139 2140 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) 2141 static struct seccomp_filter *get_nth_filter(struct task_struct *task, 2142 unsigned long filter_off) 2143 { 2144 struct seccomp_filter *orig, *filter; 2145 unsigned long count; 2146 2147 /* 2148 * Note: this is only correct because the caller should be the (ptrace) 2149 * tracer of the task, otherwise lock_task_sighand is needed. 2150 */ 2151 spin_lock_irq(&task->sighand->siglock); 2152 2153 if (task->seccomp.mode != SECCOMP_MODE_FILTER) { 2154 spin_unlock_irq(&task->sighand->siglock); 2155 return ERR_PTR(-EINVAL); 2156 } 2157 2158 orig = task->seccomp.filter; 2159 __get_seccomp_filter(orig); 2160 spin_unlock_irq(&task->sighand->siglock); 2161 2162 count = 0; 2163 for (filter = orig; filter; filter = filter->prev) 2164 count++; 2165 2166 if (filter_off >= count) { 2167 filter = ERR_PTR(-ENOENT); 2168 goto out; 2169 } 2170 2171 count -= filter_off; 2172 for (filter = orig; filter && count > 1; filter = filter->prev) 2173 count--; 2174 2175 if (WARN_ON(count != 1 || !filter)) { 2176 filter = ERR_PTR(-ENOENT); 2177 goto out; 2178 } 2179 2180 __get_seccomp_filter(filter); 2181 2182 out: 2183 __put_seccomp_filter(orig); 2184 return filter; 2185 } 2186 2187 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, 2188 void __user *data) 2189 { 2190 struct seccomp_filter *filter; 2191 struct sock_fprog_kern *fprog; 2192 long ret; 2193 2194 if (!capable(CAP_SYS_ADMIN) || 2195 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 2196 return -EACCES; 2197 } 2198 2199 filter = get_nth_filter(task, filter_off); 2200 if (IS_ERR(filter)) 2201 return PTR_ERR(filter); 2202 2203 fprog = filter->prog->orig_prog; 2204 if (!fprog) { 2205 /* This must be a new non-cBPF filter, since we save 2206 * every cBPF filter's orig_prog above when 2207 * CONFIG_CHECKPOINT_RESTORE is enabled. 2208 */ 2209 ret = -EMEDIUMTYPE; 2210 goto out; 2211 } 2212 2213 ret = fprog->len; 2214 if (!data) 2215 goto out; 2216 2217 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) 2218 ret = -EFAULT; 2219 2220 out: 2221 __put_seccomp_filter(filter); 2222 return ret; 2223 } 2224 2225 long seccomp_get_metadata(struct task_struct *task, 2226 unsigned long size, void __user *data) 2227 { 2228 long ret; 2229 struct seccomp_filter *filter; 2230 struct seccomp_metadata kmd = {}; 2231 2232 if (!capable(CAP_SYS_ADMIN) || 2233 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 2234 return -EACCES; 2235 } 2236 2237 size = min_t(unsigned long, size, sizeof(kmd)); 2238 2239 if (size < sizeof(kmd.filter_off)) 2240 return -EINVAL; 2241 2242 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) 2243 return -EFAULT; 2244 2245 filter = get_nth_filter(task, kmd.filter_off); 2246 if (IS_ERR(filter)) 2247 return PTR_ERR(filter); 2248 2249 if (filter->log) 2250 kmd.flags |= SECCOMP_FILTER_FLAG_LOG; 2251 2252 ret = size; 2253 if (copy_to_user(data, &kmd, size)) 2254 ret = -EFAULT; 2255 2256 __put_seccomp_filter(filter); 2257 return ret; 2258 } 2259 #endif 2260 2261 #ifdef CONFIG_SYSCTL 2262 2263 /* Human readable action names for friendly sysctl interaction */ 2264 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" 2265 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" 2266 #define SECCOMP_RET_TRAP_NAME "trap" 2267 #define SECCOMP_RET_ERRNO_NAME "errno" 2268 #define SECCOMP_RET_USER_NOTIF_NAME "user_notif" 2269 #define SECCOMP_RET_TRACE_NAME "trace" 2270 #define SECCOMP_RET_LOG_NAME "log" 2271 #define SECCOMP_RET_ALLOW_NAME "allow" 2272 2273 static const char seccomp_actions_avail[] = 2274 SECCOMP_RET_KILL_PROCESS_NAME " " 2275 SECCOMP_RET_KILL_THREAD_NAME " " 2276 SECCOMP_RET_TRAP_NAME " " 2277 SECCOMP_RET_ERRNO_NAME " " 2278 SECCOMP_RET_USER_NOTIF_NAME " " 2279 SECCOMP_RET_TRACE_NAME " " 2280 SECCOMP_RET_LOG_NAME " " 2281 SECCOMP_RET_ALLOW_NAME; 2282 2283 struct seccomp_log_name { 2284 u32 log; 2285 const char *name; 2286 }; 2287 2288 static const struct seccomp_log_name seccomp_log_names[] = { 2289 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, 2290 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, 2291 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, 2292 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, 2293 { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME }, 2294 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, 2295 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, 2296 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, 2297 { } 2298 }; 2299 2300 static bool seccomp_names_from_actions_logged(char *names, size_t size, 2301 u32 actions_logged, 2302 const char *sep) 2303 { 2304 const struct seccomp_log_name *cur; 2305 bool append_sep = false; 2306 2307 for (cur = seccomp_log_names; cur->name && size; cur++) { 2308 ssize_t ret; 2309 2310 if (!(actions_logged & cur->log)) 2311 continue; 2312 2313 if (append_sep) { 2314 ret = strscpy(names, sep, size); 2315 if (ret < 0) 2316 return false; 2317 2318 names += ret; 2319 size -= ret; 2320 } else 2321 append_sep = true; 2322 2323 ret = strscpy(names, cur->name, size); 2324 if (ret < 0) 2325 return false; 2326 2327 names += ret; 2328 size -= ret; 2329 } 2330 2331 return true; 2332 } 2333 2334 static bool seccomp_action_logged_from_name(u32 *action_logged, 2335 const char *name) 2336 { 2337 const struct seccomp_log_name *cur; 2338 2339 for (cur = seccomp_log_names; cur->name; cur++) { 2340 if (!strcmp(cur->name, name)) { 2341 *action_logged = cur->log; 2342 return true; 2343 } 2344 } 2345 2346 return false; 2347 } 2348 2349 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) 2350 { 2351 char *name; 2352 2353 *actions_logged = 0; 2354 while ((name = strsep(&names, " ")) && *name) { 2355 u32 action_logged = 0; 2356 2357 if (!seccomp_action_logged_from_name(&action_logged, name)) 2358 return false; 2359 2360 *actions_logged |= action_logged; 2361 } 2362 2363 return true; 2364 } 2365 2366 static int read_actions_logged(const struct ctl_table *ro_table, void *buffer, 2367 size_t *lenp, loff_t *ppos) 2368 { 2369 char names[sizeof(seccomp_actions_avail)]; 2370 struct ctl_table table; 2371 2372 memset(names, 0, sizeof(names)); 2373 2374 if (!seccomp_names_from_actions_logged(names, sizeof(names), 2375 seccomp_actions_logged, " ")) 2376 return -EINVAL; 2377 2378 table = *ro_table; 2379 table.data = names; 2380 table.maxlen = sizeof(names); 2381 return proc_dostring(&table, 0, buffer, lenp, ppos); 2382 } 2383 2384 static int write_actions_logged(const struct ctl_table *ro_table, void *buffer, 2385 size_t *lenp, loff_t *ppos, u32 *actions_logged) 2386 { 2387 char names[sizeof(seccomp_actions_avail)]; 2388 struct ctl_table table; 2389 int ret; 2390 2391 if (!capable(CAP_SYS_ADMIN)) 2392 return -EPERM; 2393 2394 memset(names, 0, sizeof(names)); 2395 2396 table = *ro_table; 2397 table.data = names; 2398 table.maxlen = sizeof(names); 2399 ret = proc_dostring(&table, 1, buffer, lenp, ppos); 2400 if (ret) 2401 return ret; 2402 2403 if (!seccomp_actions_logged_from_names(actions_logged, table.data)) 2404 return -EINVAL; 2405 2406 if (*actions_logged & SECCOMP_LOG_ALLOW) 2407 return -EINVAL; 2408 2409 seccomp_actions_logged = *actions_logged; 2410 return 0; 2411 } 2412 2413 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, 2414 int ret) 2415 { 2416 char names[sizeof(seccomp_actions_avail)]; 2417 char old_names[sizeof(seccomp_actions_avail)]; 2418 const char *new = names; 2419 const char *old = old_names; 2420 2421 if (!audit_enabled) 2422 return; 2423 2424 memset(names, 0, sizeof(names)); 2425 memset(old_names, 0, sizeof(old_names)); 2426 2427 if (ret) 2428 new = "?"; 2429 else if (!actions_logged) 2430 new = "(none)"; 2431 else if (!seccomp_names_from_actions_logged(names, sizeof(names), 2432 actions_logged, ",")) 2433 new = "?"; 2434 2435 if (!old_actions_logged) 2436 old = "(none)"; 2437 else if (!seccomp_names_from_actions_logged(old_names, 2438 sizeof(old_names), 2439 old_actions_logged, ",")) 2440 old = "?"; 2441 2442 return audit_seccomp_actions_logged(new, old, !ret); 2443 } 2444 2445 static int seccomp_actions_logged_handler(const struct ctl_table *ro_table, int write, 2446 void *buffer, size_t *lenp, 2447 loff_t *ppos) 2448 { 2449 int ret; 2450 2451 if (write) { 2452 u32 actions_logged = 0; 2453 u32 old_actions_logged = seccomp_actions_logged; 2454 2455 ret = write_actions_logged(ro_table, buffer, lenp, ppos, 2456 &actions_logged); 2457 audit_actions_logged(actions_logged, old_actions_logged, ret); 2458 } else 2459 ret = read_actions_logged(ro_table, buffer, lenp, ppos); 2460 2461 return ret; 2462 } 2463 2464 static const struct ctl_table seccomp_sysctl_table[] = { 2465 { 2466 .procname = "actions_avail", 2467 .data = (void *) &seccomp_actions_avail, 2468 .maxlen = sizeof(seccomp_actions_avail), 2469 .mode = 0444, 2470 .proc_handler = proc_dostring, 2471 }, 2472 { 2473 .procname = "actions_logged", 2474 .mode = 0644, 2475 .proc_handler = seccomp_actions_logged_handler, 2476 }, 2477 }; 2478 2479 static int __init seccomp_sysctl_init(void) 2480 { 2481 register_sysctl_init("kernel/seccomp", seccomp_sysctl_table); 2482 return 0; 2483 } 2484 2485 device_initcall(seccomp_sysctl_init) 2486 2487 #endif /* CONFIG_SYSCTL */ 2488 2489 #ifdef CONFIG_SECCOMP_CACHE_DEBUG 2490 /* Currently CONFIG_SECCOMP_CACHE_DEBUG implies SECCOMP_ARCH_NATIVE */ 2491 static void proc_pid_seccomp_cache_arch(struct seq_file *m, const char *name, 2492 const void *bitmap, size_t bitmap_size) 2493 { 2494 int nr; 2495 2496 for (nr = 0; nr < bitmap_size; nr++) { 2497 bool cached = test_bit(nr, bitmap); 2498 char *status = cached ? "ALLOW" : "FILTER"; 2499 2500 seq_printf(m, "%s %d %s\n", name, nr, status); 2501 } 2502 } 2503 2504 int proc_pid_seccomp_cache(struct seq_file *m, struct pid_namespace *ns, 2505 struct pid *pid, struct task_struct *task) 2506 { 2507 struct seccomp_filter *f; 2508 unsigned long flags; 2509 2510 /* 2511 * We don't want some sandboxed process to know what their seccomp 2512 * filters consist of. 2513 */ 2514 if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN)) 2515 return -EACCES; 2516 2517 if (!lock_task_sighand(task, &flags)) 2518 return -ESRCH; 2519 2520 f = READ_ONCE(task->seccomp.filter); 2521 if (!f) { 2522 unlock_task_sighand(task, &flags); 2523 return 0; 2524 } 2525 2526 /* prevent filter from being freed while we are printing it */ 2527 __get_seccomp_filter(f); 2528 unlock_task_sighand(task, &flags); 2529 2530 proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_NATIVE_NAME, 2531 f->cache.allow_native, 2532 SECCOMP_ARCH_NATIVE_NR); 2533 2534 #ifdef SECCOMP_ARCH_COMPAT 2535 proc_pid_seccomp_cache_arch(m, SECCOMP_ARCH_COMPAT_NAME, 2536 f->cache.allow_compat, 2537 SECCOMP_ARCH_COMPAT_NR); 2538 #endif /* SECCOMP_ARCH_COMPAT */ 2539 2540 __put_seccomp_filter(f); 2541 return 0; 2542 } 2543 #endif /* CONFIG_SECCOMP_CACHE_DEBUG */ 2544