1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/kernel/seccomp.c 4 * 5 * Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com> 6 * 7 * Copyright (C) 2012 Google, Inc. 8 * Will Drewry <wad@chromium.org> 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 17 #include <linux/refcount.h> 18 #include <linux/audit.h> 19 #include <linux/compat.h> 20 #include <linux/coredump.h> 21 #include <linux/kmemleak.h> 22 #include <linux/nospec.h> 23 #include <linux/prctl.h> 24 #include <linux/sched.h> 25 #include <linux/sched/task_stack.h> 26 #include <linux/seccomp.h> 27 #include <linux/slab.h> 28 #include <linux/syscalls.h> 29 #include <linux/sysctl.h> 30 31 #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER 32 #include <asm/syscall.h> 33 #endif 34 35 #ifdef CONFIG_SECCOMP_FILTER 36 #include <linux/filter.h> 37 #include <linux/pid.h> 38 #include <linux/ptrace.h> 39 #include <linux/security.h> 40 #include <linux/tracehook.h> 41 #include <linux/uaccess.h> 42 43 /** 44 * struct seccomp_filter - container for seccomp BPF programs 45 * 46 * @usage: reference count to manage the object lifetime. 47 * get/put helpers should be used when accessing an instance 48 * outside of a lifetime-guarded section. In general, this 49 * is only needed for handling filters shared across tasks. 50 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged 51 * @prev: points to a previously installed, or inherited, filter 52 * @prog: the BPF program to evaluate 53 * 54 * seccomp_filter objects are organized in a tree linked via the @prev 55 * pointer. For any task, it appears to be a singly-linked list starting 56 * with current->seccomp.filter, the most recently attached or inherited filter. 57 * However, multiple filters may share a @prev node, by way of fork(), which 58 * results in a unidirectional tree existing in memory. This is similar to 59 * how namespaces work. 60 * 61 * seccomp_filter objects should never be modified after being attached 62 * to a task_struct (other than @usage). 63 */ 64 struct seccomp_filter { 65 refcount_t usage; 66 bool log; 67 struct seccomp_filter *prev; 68 struct bpf_prog *prog; 69 }; 70 71 /* Limit any path through the tree to 256KB worth of instructions. */ 72 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) 73 74 /* 75 * Endianness is explicitly ignored and left for BPF program authors to manage 76 * as per the specific architecture. 77 */ 78 static void populate_seccomp_data(struct seccomp_data *sd) 79 { 80 struct task_struct *task = current; 81 struct pt_regs *regs = task_pt_regs(task); 82 unsigned long args[6]; 83 84 sd->nr = syscall_get_nr(task, regs); 85 sd->arch = syscall_get_arch(); 86 syscall_get_arguments(task, regs, 0, 6, args); 87 sd->args[0] = args[0]; 88 sd->args[1] = args[1]; 89 sd->args[2] = args[2]; 90 sd->args[3] = args[3]; 91 sd->args[4] = args[4]; 92 sd->args[5] = args[5]; 93 sd->instruction_pointer = KSTK_EIP(task); 94 } 95 96 /** 97 * seccomp_check_filter - verify seccomp filter code 98 * @filter: filter to verify 99 * @flen: length of filter 100 * 101 * Takes a previously checked filter (by bpf_check_classic) and 102 * redirects all filter code that loads struct sk_buff data 103 * and related data through seccomp_bpf_load. It also 104 * enforces length and alignment checking of those loads. 105 * 106 * Returns 0 if the rule set is legal or -EINVAL if not. 107 */ 108 static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) 109 { 110 int pc; 111 for (pc = 0; pc < flen; pc++) { 112 struct sock_filter *ftest = &filter[pc]; 113 u16 code = ftest->code; 114 u32 k = ftest->k; 115 116 switch (code) { 117 case BPF_LD | BPF_W | BPF_ABS: 118 ftest->code = BPF_LDX | BPF_W | BPF_ABS; 119 /* 32-bit aligned and not out of bounds. */ 120 if (k >= sizeof(struct seccomp_data) || k & 3) 121 return -EINVAL; 122 continue; 123 case BPF_LD | BPF_W | BPF_LEN: 124 ftest->code = BPF_LD | BPF_IMM; 125 ftest->k = sizeof(struct seccomp_data); 126 continue; 127 case BPF_LDX | BPF_W | BPF_LEN: 128 ftest->code = BPF_LDX | BPF_IMM; 129 ftest->k = sizeof(struct seccomp_data); 130 continue; 131 /* Explicitly include allowed calls. */ 132 case BPF_RET | BPF_K: 133 case BPF_RET | BPF_A: 134 case BPF_ALU | BPF_ADD | BPF_K: 135 case BPF_ALU | BPF_ADD | BPF_X: 136 case BPF_ALU | BPF_SUB | BPF_K: 137 case BPF_ALU | BPF_SUB | BPF_X: 138 case BPF_ALU | BPF_MUL | BPF_K: 139 case BPF_ALU | BPF_MUL | BPF_X: 140 case BPF_ALU | BPF_DIV | BPF_K: 141 case BPF_ALU | BPF_DIV | BPF_X: 142 case BPF_ALU | BPF_AND | BPF_K: 143 case BPF_ALU | BPF_AND | BPF_X: 144 case BPF_ALU | BPF_OR | BPF_K: 145 case BPF_ALU | BPF_OR | BPF_X: 146 case BPF_ALU | BPF_XOR | BPF_K: 147 case BPF_ALU | BPF_XOR | BPF_X: 148 case BPF_ALU | BPF_LSH | BPF_K: 149 case BPF_ALU | BPF_LSH | BPF_X: 150 case BPF_ALU | BPF_RSH | BPF_K: 151 case BPF_ALU | BPF_RSH | BPF_X: 152 case BPF_ALU | BPF_NEG: 153 case BPF_LD | BPF_IMM: 154 case BPF_LDX | BPF_IMM: 155 case BPF_MISC | BPF_TAX: 156 case BPF_MISC | BPF_TXA: 157 case BPF_LD | BPF_MEM: 158 case BPF_LDX | BPF_MEM: 159 case BPF_ST: 160 case BPF_STX: 161 case BPF_JMP | BPF_JA: 162 case BPF_JMP | BPF_JEQ | BPF_K: 163 case BPF_JMP | BPF_JEQ | BPF_X: 164 case BPF_JMP | BPF_JGE | BPF_K: 165 case BPF_JMP | BPF_JGE | BPF_X: 166 case BPF_JMP | BPF_JGT | BPF_K: 167 case BPF_JMP | BPF_JGT | BPF_X: 168 case BPF_JMP | BPF_JSET | BPF_K: 169 case BPF_JMP | BPF_JSET | BPF_X: 170 continue; 171 default: 172 return -EINVAL; 173 } 174 } 175 return 0; 176 } 177 178 /** 179 * seccomp_run_filters - evaluates all seccomp filters against @sd 180 * @sd: optional seccomp data to be passed to filters 181 * @match: stores struct seccomp_filter that resulted in the return value, 182 * unless filter returned SECCOMP_RET_ALLOW, in which case it will 183 * be unchanged. 184 * 185 * Returns valid seccomp BPF response codes. 186 */ 187 #define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL))) 188 static u32 seccomp_run_filters(const struct seccomp_data *sd, 189 struct seccomp_filter **match) 190 { 191 struct seccomp_data sd_local; 192 u32 ret = SECCOMP_RET_ALLOW; 193 /* Make sure cross-thread synced filter points somewhere sane. */ 194 struct seccomp_filter *f = 195 READ_ONCE(current->seccomp.filter); 196 197 /* Ensure unexpected behavior doesn't result in failing open. */ 198 if (unlikely(WARN_ON(f == NULL))) 199 return SECCOMP_RET_KILL_PROCESS; 200 201 if (!sd) { 202 populate_seccomp_data(&sd_local); 203 sd = &sd_local; 204 } 205 206 /* 207 * All filters in the list are evaluated and the lowest BPF return 208 * value always takes priority (ignoring the DATA). 209 */ 210 for (; f; f = f->prev) { 211 u32 cur_ret = BPF_PROG_RUN(f->prog, sd); 212 213 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { 214 ret = cur_ret; 215 *match = f; 216 } 217 } 218 return ret; 219 } 220 #endif /* CONFIG_SECCOMP_FILTER */ 221 222 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) 223 { 224 assert_spin_locked(¤t->sighand->siglock); 225 226 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) 227 return false; 228 229 return true; 230 } 231 232 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } 233 234 static inline void seccomp_assign_mode(struct task_struct *task, 235 unsigned long seccomp_mode, 236 unsigned long flags) 237 { 238 assert_spin_locked(&task->sighand->siglock); 239 240 task->seccomp.mode = seccomp_mode; 241 /* 242 * Make sure TIF_SECCOMP cannot be set before the mode (and 243 * filter) is set. 244 */ 245 smp_mb__before_atomic(); 246 /* Assume default seccomp processes want spec flaw mitigation. */ 247 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) 248 arch_seccomp_spec_mitigate(task); 249 set_tsk_thread_flag(task, TIF_SECCOMP); 250 } 251 252 #ifdef CONFIG_SECCOMP_FILTER 253 /* Returns 1 if the parent is an ancestor of the child. */ 254 static int is_ancestor(struct seccomp_filter *parent, 255 struct seccomp_filter *child) 256 { 257 /* NULL is the root ancestor. */ 258 if (parent == NULL) 259 return 1; 260 for (; child; child = child->prev) 261 if (child == parent) 262 return 1; 263 return 0; 264 } 265 266 /** 267 * seccomp_can_sync_threads: checks if all threads can be synchronized 268 * 269 * Expects sighand and cred_guard_mutex locks to be held. 270 * 271 * Returns 0 on success, -ve on error, or the pid of a thread which was 272 * either not in the correct seccomp mode or it did not have an ancestral 273 * seccomp filter. 274 */ 275 static inline pid_t seccomp_can_sync_threads(void) 276 { 277 struct task_struct *thread, *caller; 278 279 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 280 assert_spin_locked(¤t->sighand->siglock); 281 282 /* Validate all threads being eligible for synchronization. */ 283 caller = current; 284 for_each_thread(caller, thread) { 285 pid_t failed; 286 287 /* Skip current, since it is initiating the sync. */ 288 if (thread == caller) 289 continue; 290 291 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || 292 (thread->seccomp.mode == SECCOMP_MODE_FILTER && 293 is_ancestor(thread->seccomp.filter, 294 caller->seccomp.filter))) 295 continue; 296 297 /* Return the first thread that cannot be synchronized. */ 298 failed = task_pid_vnr(thread); 299 /* If the pid cannot be resolved, then return -ESRCH */ 300 if (unlikely(WARN_ON(failed == 0))) 301 failed = -ESRCH; 302 return failed; 303 } 304 305 return 0; 306 } 307 308 /** 309 * seccomp_sync_threads: sets all threads to use current's filter 310 * 311 * Expects sighand and cred_guard_mutex locks to be held, and for 312 * seccomp_can_sync_threads() to have returned success already 313 * without dropping the locks. 314 * 315 */ 316 static inline void seccomp_sync_threads(unsigned long flags) 317 { 318 struct task_struct *thread, *caller; 319 320 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 321 assert_spin_locked(¤t->sighand->siglock); 322 323 /* Synchronize all threads. */ 324 caller = current; 325 for_each_thread(caller, thread) { 326 /* Skip current, since it needs no changes. */ 327 if (thread == caller) 328 continue; 329 330 /* Get a task reference for the new leaf node. */ 331 get_seccomp_filter(caller); 332 /* 333 * Drop the task reference to the shared ancestor since 334 * current's path will hold a reference. (This also 335 * allows a put before the assignment.) 336 */ 337 put_seccomp_filter(thread); 338 smp_store_release(&thread->seccomp.filter, 339 caller->seccomp.filter); 340 341 /* 342 * Don't let an unprivileged task work around 343 * the no_new_privs restriction by creating 344 * a thread that sets it up, enters seccomp, 345 * then dies. 346 */ 347 if (task_no_new_privs(caller)) 348 task_set_no_new_privs(thread); 349 350 /* 351 * Opt the other thread into seccomp if needed. 352 * As threads are considered to be trust-realm 353 * equivalent (see ptrace_may_access), it is safe to 354 * allow one thread to transition the other. 355 */ 356 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) 357 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, 358 flags); 359 } 360 } 361 362 /** 363 * seccomp_prepare_filter: Prepares a seccomp filter for use. 364 * @fprog: BPF program to install 365 * 366 * Returns filter on success or an ERR_PTR on failure. 367 */ 368 static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) 369 { 370 struct seccomp_filter *sfilter; 371 int ret; 372 const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); 373 374 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) 375 return ERR_PTR(-EINVAL); 376 377 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); 378 379 /* 380 * Installing a seccomp filter requires that the task has 381 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. 382 * This avoids scenarios where unprivileged tasks can affect the 383 * behavior of privileged children. 384 */ 385 if (!task_no_new_privs(current) && 386 security_capable_noaudit(current_cred(), current_user_ns(), 387 CAP_SYS_ADMIN) != 0) 388 return ERR_PTR(-EACCES); 389 390 /* Allocate a new seccomp_filter */ 391 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); 392 if (!sfilter) 393 return ERR_PTR(-ENOMEM); 394 395 ret = bpf_prog_create_from_user(&sfilter->prog, fprog, 396 seccomp_check_filter, save_orig); 397 if (ret < 0) { 398 kfree(sfilter); 399 return ERR_PTR(ret); 400 } 401 402 refcount_set(&sfilter->usage, 1); 403 404 return sfilter; 405 } 406 407 /** 408 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog 409 * @user_filter: pointer to the user data containing a sock_fprog. 410 * 411 * Returns 0 on success and non-zero otherwise. 412 */ 413 static struct seccomp_filter * 414 seccomp_prepare_user_filter(const char __user *user_filter) 415 { 416 struct sock_fprog fprog; 417 struct seccomp_filter *filter = ERR_PTR(-EFAULT); 418 419 #ifdef CONFIG_COMPAT 420 if (in_compat_syscall()) { 421 struct compat_sock_fprog fprog32; 422 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) 423 goto out; 424 fprog.len = fprog32.len; 425 fprog.filter = compat_ptr(fprog32.filter); 426 } else /* falls through to the if below. */ 427 #endif 428 if (copy_from_user(&fprog, user_filter, sizeof(fprog))) 429 goto out; 430 filter = seccomp_prepare_filter(&fprog); 431 out: 432 return filter; 433 } 434 435 /** 436 * seccomp_attach_filter: validate and attach filter 437 * @flags: flags to change filter behavior 438 * @filter: seccomp filter to add to the current process 439 * 440 * Caller must be holding current->sighand->siglock lock. 441 * 442 * Returns 0 on success, -ve on error. 443 */ 444 static long seccomp_attach_filter(unsigned int flags, 445 struct seccomp_filter *filter) 446 { 447 unsigned long total_insns; 448 struct seccomp_filter *walker; 449 450 assert_spin_locked(¤t->sighand->siglock); 451 452 /* Validate resulting filter length. */ 453 total_insns = filter->prog->len; 454 for (walker = current->seccomp.filter; walker; walker = walker->prev) 455 total_insns += walker->prog->len + 4; /* 4 instr penalty */ 456 if (total_insns > MAX_INSNS_PER_PATH) 457 return -ENOMEM; 458 459 /* If thread sync has been requested, check that it is possible. */ 460 if (flags & SECCOMP_FILTER_FLAG_TSYNC) { 461 int ret; 462 463 ret = seccomp_can_sync_threads(); 464 if (ret) 465 return ret; 466 } 467 468 /* Set log flag, if present. */ 469 if (flags & SECCOMP_FILTER_FLAG_LOG) 470 filter->log = true; 471 472 /* 473 * If there is an existing filter, make it the prev and don't drop its 474 * task reference. 475 */ 476 filter->prev = current->seccomp.filter; 477 current->seccomp.filter = filter; 478 479 /* Now that the new filter is in place, synchronize to all threads. */ 480 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 481 seccomp_sync_threads(flags); 482 483 return 0; 484 } 485 486 static void __get_seccomp_filter(struct seccomp_filter *filter) 487 { 488 /* Reference count is bounded by the number of total processes. */ 489 refcount_inc(&filter->usage); 490 } 491 492 /* get_seccomp_filter - increments the reference count of the filter on @tsk */ 493 void get_seccomp_filter(struct task_struct *tsk) 494 { 495 struct seccomp_filter *orig = tsk->seccomp.filter; 496 if (!orig) 497 return; 498 __get_seccomp_filter(orig); 499 } 500 501 static inline void seccomp_filter_free(struct seccomp_filter *filter) 502 { 503 if (filter) { 504 bpf_prog_destroy(filter->prog); 505 kfree(filter); 506 } 507 } 508 509 static void __put_seccomp_filter(struct seccomp_filter *orig) 510 { 511 /* Clean up single-reference branches iteratively. */ 512 while (orig && refcount_dec_and_test(&orig->usage)) { 513 struct seccomp_filter *freeme = orig; 514 orig = orig->prev; 515 seccomp_filter_free(freeme); 516 } 517 } 518 519 /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ 520 void put_seccomp_filter(struct task_struct *tsk) 521 { 522 __put_seccomp_filter(tsk->seccomp.filter); 523 } 524 525 static void seccomp_init_siginfo(siginfo_t *info, int syscall, int reason) 526 { 527 clear_siginfo(info); 528 info->si_signo = SIGSYS; 529 info->si_code = SYS_SECCOMP; 530 info->si_call_addr = (void __user *)KSTK_EIP(current); 531 info->si_errno = reason; 532 info->si_arch = syscall_get_arch(); 533 info->si_syscall = syscall; 534 } 535 536 /** 537 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation 538 * @syscall: syscall number to send to userland 539 * @reason: filter-supplied reason code to send to userland (via si_errno) 540 * 541 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. 542 */ 543 static void seccomp_send_sigsys(int syscall, int reason) 544 { 545 struct siginfo info; 546 seccomp_init_siginfo(&info, syscall, reason); 547 force_sig_info(SIGSYS, &info, current); 548 } 549 #endif /* CONFIG_SECCOMP_FILTER */ 550 551 /* For use with seccomp_actions_logged */ 552 #define SECCOMP_LOG_KILL_PROCESS (1 << 0) 553 #define SECCOMP_LOG_KILL_THREAD (1 << 1) 554 #define SECCOMP_LOG_TRAP (1 << 2) 555 #define SECCOMP_LOG_ERRNO (1 << 3) 556 #define SECCOMP_LOG_TRACE (1 << 4) 557 #define SECCOMP_LOG_LOG (1 << 5) 558 #define SECCOMP_LOG_ALLOW (1 << 6) 559 560 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | 561 SECCOMP_LOG_KILL_THREAD | 562 SECCOMP_LOG_TRAP | 563 SECCOMP_LOG_ERRNO | 564 SECCOMP_LOG_TRACE | 565 SECCOMP_LOG_LOG; 566 567 static inline void seccomp_log(unsigned long syscall, long signr, u32 action, 568 bool requested) 569 { 570 bool log = false; 571 572 switch (action) { 573 case SECCOMP_RET_ALLOW: 574 break; 575 case SECCOMP_RET_TRAP: 576 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; 577 break; 578 case SECCOMP_RET_ERRNO: 579 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; 580 break; 581 case SECCOMP_RET_TRACE: 582 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; 583 break; 584 case SECCOMP_RET_LOG: 585 log = seccomp_actions_logged & SECCOMP_LOG_LOG; 586 break; 587 case SECCOMP_RET_KILL_THREAD: 588 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; 589 break; 590 case SECCOMP_RET_KILL_PROCESS: 591 default: 592 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; 593 } 594 595 /* 596 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the 597 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence 598 * any action from being logged by removing the action name from the 599 * seccomp_actions_logged sysctl. 600 */ 601 if (!log) 602 return; 603 604 audit_seccomp(syscall, signr, action); 605 } 606 607 /* 608 * Secure computing mode 1 allows only read/write/exit/sigreturn. 609 * To be fully secure this must be combined with rlimit 610 * to limit the stack allocations too. 611 */ 612 static const int mode1_syscalls[] = { 613 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, 614 0, /* null terminated */ 615 }; 616 617 static void __secure_computing_strict(int this_syscall) 618 { 619 const int *syscall_whitelist = mode1_syscalls; 620 #ifdef CONFIG_COMPAT 621 if (in_compat_syscall()) 622 syscall_whitelist = get_compat_mode1_syscalls(); 623 #endif 624 do { 625 if (*syscall_whitelist == this_syscall) 626 return; 627 } while (*++syscall_whitelist); 628 629 #ifdef SECCOMP_DEBUG 630 dump_stack(); 631 #endif 632 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); 633 do_exit(SIGKILL); 634 } 635 636 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER 637 void secure_computing_strict(int this_syscall) 638 { 639 int mode = current->seccomp.mode; 640 641 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 642 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 643 return; 644 645 if (mode == SECCOMP_MODE_DISABLED) 646 return; 647 else if (mode == SECCOMP_MODE_STRICT) 648 __secure_computing_strict(this_syscall); 649 else 650 BUG(); 651 } 652 #else 653 654 #ifdef CONFIG_SECCOMP_FILTER 655 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 656 const bool recheck_after_trace) 657 { 658 u32 filter_ret, action; 659 struct seccomp_filter *match = NULL; 660 int data; 661 662 /* 663 * Make sure that any changes to mode from another thread have 664 * been seen after TIF_SECCOMP was seen. 665 */ 666 rmb(); 667 668 filter_ret = seccomp_run_filters(sd, &match); 669 data = filter_ret & SECCOMP_RET_DATA; 670 action = filter_ret & SECCOMP_RET_ACTION_FULL; 671 672 switch (action) { 673 case SECCOMP_RET_ERRNO: 674 /* Set low-order bits as an errno, capped at MAX_ERRNO. */ 675 if (data > MAX_ERRNO) 676 data = MAX_ERRNO; 677 syscall_set_return_value(current, task_pt_regs(current), 678 -data, 0); 679 goto skip; 680 681 case SECCOMP_RET_TRAP: 682 /* Show the handler the original registers. */ 683 syscall_rollback(current, task_pt_regs(current)); 684 /* Let the filter pass back 16 bits of data. */ 685 seccomp_send_sigsys(this_syscall, data); 686 goto skip; 687 688 case SECCOMP_RET_TRACE: 689 /* We've been put in this state by the ptracer already. */ 690 if (recheck_after_trace) 691 return 0; 692 693 /* ENOSYS these calls if there is no tracer attached. */ 694 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { 695 syscall_set_return_value(current, 696 task_pt_regs(current), 697 -ENOSYS, 0); 698 goto skip; 699 } 700 701 /* Allow the BPF to provide the event message */ 702 ptrace_event(PTRACE_EVENT_SECCOMP, data); 703 /* 704 * The delivery of a fatal signal during event 705 * notification may silently skip tracer notification, 706 * which could leave us with a potentially unmodified 707 * syscall that the tracer would have liked to have 708 * changed. Since the process is about to die, we just 709 * force the syscall to be skipped and let the signal 710 * kill the process and correctly handle any tracer exit 711 * notifications. 712 */ 713 if (fatal_signal_pending(current)) 714 goto skip; 715 /* Check if the tracer forced the syscall to be skipped. */ 716 this_syscall = syscall_get_nr(current, task_pt_regs(current)); 717 if (this_syscall < 0) 718 goto skip; 719 720 /* 721 * Recheck the syscall, since it may have changed. This 722 * intentionally uses a NULL struct seccomp_data to force 723 * a reload of all registers. This does not goto skip since 724 * a skip would have already been reported. 725 */ 726 if (__seccomp_filter(this_syscall, NULL, true)) 727 return -1; 728 729 return 0; 730 731 case SECCOMP_RET_LOG: 732 seccomp_log(this_syscall, 0, action, true); 733 return 0; 734 735 case SECCOMP_RET_ALLOW: 736 /* 737 * Note that the "match" filter will always be NULL for 738 * this action since SECCOMP_RET_ALLOW is the starting 739 * state in seccomp_run_filters(). 740 */ 741 return 0; 742 743 case SECCOMP_RET_KILL_THREAD: 744 case SECCOMP_RET_KILL_PROCESS: 745 default: 746 seccomp_log(this_syscall, SIGSYS, action, true); 747 /* Dump core only if this is the last remaining thread. */ 748 if (action == SECCOMP_RET_KILL_PROCESS || 749 get_nr_threads(current) == 1) { 750 siginfo_t info; 751 752 /* Show the original registers in the dump. */ 753 syscall_rollback(current, task_pt_regs(current)); 754 /* Trigger a manual coredump since do_exit skips it. */ 755 seccomp_init_siginfo(&info, this_syscall, data); 756 do_coredump(&info); 757 } 758 if (action == SECCOMP_RET_KILL_PROCESS) 759 do_group_exit(SIGSYS); 760 else 761 do_exit(SIGSYS); 762 } 763 764 unreachable(); 765 766 skip: 767 seccomp_log(this_syscall, 0, action, match ? match->log : false); 768 return -1; 769 } 770 #else 771 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 772 const bool recheck_after_trace) 773 { 774 BUG(); 775 } 776 #endif 777 778 int __secure_computing(const struct seccomp_data *sd) 779 { 780 int mode = current->seccomp.mode; 781 int this_syscall; 782 783 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 784 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 785 return 0; 786 787 this_syscall = sd ? sd->nr : 788 syscall_get_nr(current, task_pt_regs(current)); 789 790 switch (mode) { 791 case SECCOMP_MODE_STRICT: 792 __secure_computing_strict(this_syscall); /* may call do_exit */ 793 return 0; 794 case SECCOMP_MODE_FILTER: 795 return __seccomp_filter(this_syscall, sd, false); 796 default: 797 BUG(); 798 } 799 } 800 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ 801 802 long prctl_get_seccomp(void) 803 { 804 return current->seccomp.mode; 805 } 806 807 /** 808 * seccomp_set_mode_strict: internal function for setting strict seccomp 809 * 810 * Once current->seccomp.mode is non-zero, it may not be changed. 811 * 812 * Returns 0 on success or -EINVAL on failure. 813 */ 814 static long seccomp_set_mode_strict(void) 815 { 816 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; 817 long ret = -EINVAL; 818 819 spin_lock_irq(¤t->sighand->siglock); 820 821 if (!seccomp_may_assign_mode(seccomp_mode)) 822 goto out; 823 824 #ifdef TIF_NOTSC 825 disable_TSC(); 826 #endif 827 seccomp_assign_mode(current, seccomp_mode, 0); 828 ret = 0; 829 830 out: 831 spin_unlock_irq(¤t->sighand->siglock); 832 833 return ret; 834 } 835 836 #ifdef CONFIG_SECCOMP_FILTER 837 /** 838 * seccomp_set_mode_filter: internal function for setting seccomp filter 839 * @flags: flags to change filter behavior 840 * @filter: struct sock_fprog containing filter 841 * 842 * This function may be called repeatedly to install additional filters. 843 * Every filter successfully installed will be evaluated (in reverse order) 844 * for each system call the task makes. 845 * 846 * Once current->seccomp.mode is non-zero, it may not be changed. 847 * 848 * Returns 0 on success or -EINVAL on failure. 849 */ 850 static long seccomp_set_mode_filter(unsigned int flags, 851 const char __user *filter) 852 { 853 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; 854 struct seccomp_filter *prepared = NULL; 855 long ret = -EINVAL; 856 857 /* Validate flags. */ 858 if (flags & ~SECCOMP_FILTER_FLAG_MASK) 859 return -EINVAL; 860 861 /* Prepare the new filter before holding any locks. */ 862 prepared = seccomp_prepare_user_filter(filter); 863 if (IS_ERR(prepared)) 864 return PTR_ERR(prepared); 865 866 /* 867 * Make sure we cannot change seccomp or nnp state via TSYNC 868 * while another thread is in the middle of calling exec. 869 */ 870 if (flags & SECCOMP_FILTER_FLAG_TSYNC && 871 mutex_lock_killable(¤t->signal->cred_guard_mutex)) 872 goto out_free; 873 874 spin_lock_irq(¤t->sighand->siglock); 875 876 if (!seccomp_may_assign_mode(seccomp_mode)) 877 goto out; 878 879 ret = seccomp_attach_filter(flags, prepared); 880 if (ret) 881 goto out; 882 /* Do not free the successfully attached filter. */ 883 prepared = NULL; 884 885 seccomp_assign_mode(current, seccomp_mode, flags); 886 out: 887 spin_unlock_irq(¤t->sighand->siglock); 888 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 889 mutex_unlock(¤t->signal->cred_guard_mutex); 890 out_free: 891 seccomp_filter_free(prepared); 892 return ret; 893 } 894 #else 895 static inline long seccomp_set_mode_filter(unsigned int flags, 896 const char __user *filter) 897 { 898 return -EINVAL; 899 } 900 #endif 901 902 static long seccomp_get_action_avail(const char __user *uaction) 903 { 904 u32 action; 905 906 if (copy_from_user(&action, uaction, sizeof(action))) 907 return -EFAULT; 908 909 switch (action) { 910 case SECCOMP_RET_KILL_PROCESS: 911 case SECCOMP_RET_KILL_THREAD: 912 case SECCOMP_RET_TRAP: 913 case SECCOMP_RET_ERRNO: 914 case SECCOMP_RET_TRACE: 915 case SECCOMP_RET_LOG: 916 case SECCOMP_RET_ALLOW: 917 break; 918 default: 919 return -EOPNOTSUPP; 920 } 921 922 return 0; 923 } 924 925 /* Common entry point for both prctl and syscall. */ 926 static long do_seccomp(unsigned int op, unsigned int flags, 927 const char __user *uargs) 928 { 929 switch (op) { 930 case SECCOMP_SET_MODE_STRICT: 931 if (flags != 0 || uargs != NULL) 932 return -EINVAL; 933 return seccomp_set_mode_strict(); 934 case SECCOMP_SET_MODE_FILTER: 935 return seccomp_set_mode_filter(flags, uargs); 936 case SECCOMP_GET_ACTION_AVAIL: 937 if (flags != 0) 938 return -EINVAL; 939 940 return seccomp_get_action_avail(uargs); 941 default: 942 return -EINVAL; 943 } 944 } 945 946 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, 947 const char __user *, uargs) 948 { 949 return do_seccomp(op, flags, uargs); 950 } 951 952 /** 953 * prctl_set_seccomp: configures current->seccomp.mode 954 * @seccomp_mode: requested mode to use 955 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER 956 * 957 * Returns 0 on success or -EINVAL on failure. 958 */ 959 long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) 960 { 961 unsigned int op; 962 char __user *uargs; 963 964 switch (seccomp_mode) { 965 case SECCOMP_MODE_STRICT: 966 op = SECCOMP_SET_MODE_STRICT; 967 /* 968 * Setting strict mode through prctl always ignored filter, 969 * so make sure it is always NULL here to pass the internal 970 * check in do_seccomp(). 971 */ 972 uargs = NULL; 973 break; 974 case SECCOMP_MODE_FILTER: 975 op = SECCOMP_SET_MODE_FILTER; 976 uargs = filter; 977 break; 978 default: 979 return -EINVAL; 980 } 981 982 /* prctl interface doesn't have flags, so they are always zero. */ 983 return do_seccomp(op, 0, uargs); 984 } 985 986 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) 987 static struct seccomp_filter *get_nth_filter(struct task_struct *task, 988 unsigned long filter_off) 989 { 990 struct seccomp_filter *orig, *filter; 991 unsigned long count; 992 993 /* 994 * Note: this is only correct because the caller should be the (ptrace) 995 * tracer of the task, otherwise lock_task_sighand is needed. 996 */ 997 spin_lock_irq(&task->sighand->siglock); 998 999 if (task->seccomp.mode != SECCOMP_MODE_FILTER) { 1000 spin_unlock_irq(&task->sighand->siglock); 1001 return ERR_PTR(-EINVAL); 1002 } 1003 1004 orig = task->seccomp.filter; 1005 __get_seccomp_filter(orig); 1006 spin_unlock_irq(&task->sighand->siglock); 1007 1008 count = 0; 1009 for (filter = orig; filter; filter = filter->prev) 1010 count++; 1011 1012 if (filter_off >= count) { 1013 filter = ERR_PTR(-ENOENT); 1014 goto out; 1015 } 1016 1017 count -= filter_off; 1018 for (filter = orig; filter && count > 1; filter = filter->prev) 1019 count--; 1020 1021 if (WARN_ON(count != 1 || !filter)) { 1022 filter = ERR_PTR(-ENOENT); 1023 goto out; 1024 } 1025 1026 __get_seccomp_filter(filter); 1027 1028 out: 1029 __put_seccomp_filter(orig); 1030 return filter; 1031 } 1032 1033 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, 1034 void __user *data) 1035 { 1036 struct seccomp_filter *filter; 1037 struct sock_fprog_kern *fprog; 1038 long ret; 1039 1040 if (!capable(CAP_SYS_ADMIN) || 1041 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1042 return -EACCES; 1043 } 1044 1045 filter = get_nth_filter(task, filter_off); 1046 if (IS_ERR(filter)) 1047 return PTR_ERR(filter); 1048 1049 fprog = filter->prog->orig_prog; 1050 if (!fprog) { 1051 /* This must be a new non-cBPF filter, since we save 1052 * every cBPF filter's orig_prog above when 1053 * CONFIG_CHECKPOINT_RESTORE is enabled. 1054 */ 1055 ret = -EMEDIUMTYPE; 1056 goto out; 1057 } 1058 1059 ret = fprog->len; 1060 if (!data) 1061 goto out; 1062 1063 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) 1064 ret = -EFAULT; 1065 1066 out: 1067 __put_seccomp_filter(filter); 1068 return ret; 1069 } 1070 1071 long seccomp_get_metadata(struct task_struct *task, 1072 unsigned long size, void __user *data) 1073 { 1074 long ret; 1075 struct seccomp_filter *filter; 1076 struct seccomp_metadata kmd = {}; 1077 1078 if (!capable(CAP_SYS_ADMIN) || 1079 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1080 return -EACCES; 1081 } 1082 1083 size = min_t(unsigned long, size, sizeof(kmd)); 1084 1085 if (size < sizeof(kmd.filter_off)) 1086 return -EINVAL; 1087 1088 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) 1089 return -EFAULT; 1090 1091 filter = get_nth_filter(task, kmd.filter_off); 1092 if (IS_ERR(filter)) 1093 return PTR_ERR(filter); 1094 1095 if (filter->log) 1096 kmd.flags |= SECCOMP_FILTER_FLAG_LOG; 1097 1098 ret = size; 1099 if (copy_to_user(data, &kmd, size)) 1100 ret = -EFAULT; 1101 1102 __put_seccomp_filter(filter); 1103 return ret; 1104 } 1105 #endif 1106 1107 #ifdef CONFIG_SYSCTL 1108 1109 /* Human readable action names for friendly sysctl interaction */ 1110 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" 1111 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" 1112 #define SECCOMP_RET_TRAP_NAME "trap" 1113 #define SECCOMP_RET_ERRNO_NAME "errno" 1114 #define SECCOMP_RET_TRACE_NAME "trace" 1115 #define SECCOMP_RET_LOG_NAME "log" 1116 #define SECCOMP_RET_ALLOW_NAME "allow" 1117 1118 static const char seccomp_actions_avail[] = 1119 SECCOMP_RET_KILL_PROCESS_NAME " " 1120 SECCOMP_RET_KILL_THREAD_NAME " " 1121 SECCOMP_RET_TRAP_NAME " " 1122 SECCOMP_RET_ERRNO_NAME " " 1123 SECCOMP_RET_TRACE_NAME " " 1124 SECCOMP_RET_LOG_NAME " " 1125 SECCOMP_RET_ALLOW_NAME; 1126 1127 struct seccomp_log_name { 1128 u32 log; 1129 const char *name; 1130 }; 1131 1132 static const struct seccomp_log_name seccomp_log_names[] = { 1133 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, 1134 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, 1135 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, 1136 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, 1137 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, 1138 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, 1139 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, 1140 { } 1141 }; 1142 1143 static bool seccomp_names_from_actions_logged(char *names, size_t size, 1144 u32 actions_logged, 1145 const char *sep) 1146 { 1147 const struct seccomp_log_name *cur; 1148 bool append_sep = false; 1149 1150 for (cur = seccomp_log_names; cur->name && size; cur++) { 1151 ssize_t ret; 1152 1153 if (!(actions_logged & cur->log)) 1154 continue; 1155 1156 if (append_sep) { 1157 ret = strscpy(names, sep, size); 1158 if (ret < 0) 1159 return false; 1160 1161 names += ret; 1162 size -= ret; 1163 } else 1164 append_sep = true; 1165 1166 ret = strscpy(names, cur->name, size); 1167 if (ret < 0) 1168 return false; 1169 1170 names += ret; 1171 size -= ret; 1172 } 1173 1174 return true; 1175 } 1176 1177 static bool seccomp_action_logged_from_name(u32 *action_logged, 1178 const char *name) 1179 { 1180 const struct seccomp_log_name *cur; 1181 1182 for (cur = seccomp_log_names; cur->name; cur++) { 1183 if (!strcmp(cur->name, name)) { 1184 *action_logged = cur->log; 1185 return true; 1186 } 1187 } 1188 1189 return false; 1190 } 1191 1192 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) 1193 { 1194 char *name; 1195 1196 *actions_logged = 0; 1197 while ((name = strsep(&names, " ")) && *name) { 1198 u32 action_logged = 0; 1199 1200 if (!seccomp_action_logged_from_name(&action_logged, name)) 1201 return false; 1202 1203 *actions_logged |= action_logged; 1204 } 1205 1206 return true; 1207 } 1208 1209 static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1210 size_t *lenp, loff_t *ppos) 1211 { 1212 char names[sizeof(seccomp_actions_avail)]; 1213 struct ctl_table table; 1214 1215 memset(names, 0, sizeof(names)); 1216 1217 if (!seccomp_names_from_actions_logged(names, sizeof(names), 1218 seccomp_actions_logged, " ")) 1219 return -EINVAL; 1220 1221 table = *ro_table; 1222 table.data = names; 1223 table.maxlen = sizeof(names); 1224 return proc_dostring(&table, 0, buffer, lenp, ppos); 1225 } 1226 1227 static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1228 size_t *lenp, loff_t *ppos, u32 *actions_logged) 1229 { 1230 char names[sizeof(seccomp_actions_avail)]; 1231 struct ctl_table table; 1232 int ret; 1233 1234 if (!capable(CAP_SYS_ADMIN)) 1235 return -EPERM; 1236 1237 memset(names, 0, sizeof(names)); 1238 1239 table = *ro_table; 1240 table.data = names; 1241 table.maxlen = sizeof(names); 1242 ret = proc_dostring(&table, 1, buffer, lenp, ppos); 1243 if (ret) 1244 return ret; 1245 1246 if (!seccomp_actions_logged_from_names(actions_logged, table.data)) 1247 return -EINVAL; 1248 1249 if (*actions_logged & SECCOMP_LOG_ALLOW) 1250 return -EINVAL; 1251 1252 seccomp_actions_logged = *actions_logged; 1253 return 0; 1254 } 1255 1256 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, 1257 int ret) 1258 { 1259 char names[sizeof(seccomp_actions_avail)]; 1260 char old_names[sizeof(seccomp_actions_avail)]; 1261 const char *new = names; 1262 const char *old = old_names; 1263 1264 if (!audit_enabled) 1265 return; 1266 1267 memset(names, 0, sizeof(names)); 1268 memset(old_names, 0, sizeof(old_names)); 1269 1270 if (ret) 1271 new = "?"; 1272 else if (!actions_logged) 1273 new = "(none)"; 1274 else if (!seccomp_names_from_actions_logged(names, sizeof(names), 1275 actions_logged, ",")) 1276 new = "?"; 1277 1278 if (!old_actions_logged) 1279 old = "(none)"; 1280 else if (!seccomp_names_from_actions_logged(old_names, 1281 sizeof(old_names), 1282 old_actions_logged, ",")) 1283 old = "?"; 1284 1285 return audit_seccomp_actions_logged(new, old, !ret); 1286 } 1287 1288 static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write, 1289 void __user *buffer, size_t *lenp, 1290 loff_t *ppos) 1291 { 1292 int ret; 1293 1294 if (write) { 1295 u32 actions_logged = 0; 1296 u32 old_actions_logged = seccomp_actions_logged; 1297 1298 ret = write_actions_logged(ro_table, buffer, lenp, ppos, 1299 &actions_logged); 1300 audit_actions_logged(actions_logged, old_actions_logged, ret); 1301 } else 1302 ret = read_actions_logged(ro_table, buffer, lenp, ppos); 1303 1304 return ret; 1305 } 1306 1307 static struct ctl_path seccomp_sysctl_path[] = { 1308 { .procname = "kernel", }, 1309 { .procname = "seccomp", }, 1310 { } 1311 }; 1312 1313 static struct ctl_table seccomp_sysctl_table[] = { 1314 { 1315 .procname = "actions_avail", 1316 .data = (void *) &seccomp_actions_avail, 1317 .maxlen = sizeof(seccomp_actions_avail), 1318 .mode = 0444, 1319 .proc_handler = proc_dostring, 1320 }, 1321 { 1322 .procname = "actions_logged", 1323 .mode = 0644, 1324 .proc_handler = seccomp_actions_logged_handler, 1325 }, 1326 { } 1327 }; 1328 1329 static int __init seccomp_sysctl_init(void) 1330 { 1331 struct ctl_table_header *hdr; 1332 1333 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table); 1334 if (!hdr) 1335 pr_warn("seccomp: sysctl registration failed\n"); 1336 else 1337 kmemleak_not_leak(hdr); 1338 1339 return 0; 1340 } 1341 1342 device_initcall(seccomp_sysctl_init) 1343 1344 #endif /* CONFIG_SYSCTL */ 1345