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/file.h> 37 #include <linux/filter.h> 38 #include <linux/pid.h> 39 #include <linux/ptrace.h> 40 #include <linux/security.h> 41 #include <linux/tracehook.h> 42 #include <linux/uaccess.h> 43 #include <linux/anon_inodes.h> 44 45 enum notify_state { 46 SECCOMP_NOTIFY_INIT, 47 SECCOMP_NOTIFY_SENT, 48 SECCOMP_NOTIFY_REPLIED, 49 }; 50 51 struct seccomp_knotif { 52 /* The struct pid of the task whose filter triggered the notification */ 53 struct task_struct *task; 54 55 /* The "cookie" for this request; this is unique for this filter. */ 56 u64 id; 57 58 /* 59 * The seccomp data. This pointer is valid the entire time this 60 * notification is active, since it comes from __seccomp_filter which 61 * eclipses the entire lifecycle here. 62 */ 63 const struct seccomp_data *data; 64 65 /* 66 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a 67 * struct seccomp_knotif is created and starts out in INIT. Once the 68 * handler reads the notification off of an FD, it transitions to SENT. 69 * If a signal is received the state transitions back to INIT and 70 * another message is sent. When the userspace handler replies, state 71 * transitions to REPLIED. 72 */ 73 enum notify_state state; 74 75 /* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */ 76 int error; 77 long val; 78 u32 flags; 79 80 /* Signals when this has entered SECCOMP_NOTIFY_REPLIED */ 81 struct completion ready; 82 83 struct list_head list; 84 }; 85 86 /** 87 * struct notification - container for seccomp userspace notifications. Since 88 * most seccomp filters will not have notification listeners attached and this 89 * structure is fairly large, we store the notification-specific stuff in a 90 * separate structure. 91 * 92 * @request: A semaphore that users of this notification can wait on for 93 * changes. Actual reads and writes are still controlled with 94 * filter->notify_lock. 95 * @next_id: The id of the next request. 96 * @notifications: A list of struct seccomp_knotif elements. 97 * @wqh: A wait queue for poll. 98 */ 99 struct notification { 100 struct semaphore request; 101 u64 next_id; 102 struct list_head notifications; 103 wait_queue_head_t wqh; 104 }; 105 106 /** 107 * struct seccomp_filter - container for seccomp BPF programs 108 * 109 * @usage: reference count to manage the object lifetime. 110 * get/put helpers should be used when accessing an instance 111 * outside of a lifetime-guarded section. In general, this 112 * is only needed for handling filters shared across tasks. 113 * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged 114 * @prev: points to a previously installed, or inherited, filter 115 * @prog: the BPF program to evaluate 116 * @notif: the struct that holds all notification related information 117 * @notify_lock: A lock for all notification-related accesses. 118 * 119 * seccomp_filter objects are organized in a tree linked via the @prev 120 * pointer. For any task, it appears to be a singly-linked list starting 121 * with current->seccomp.filter, the most recently attached or inherited filter. 122 * However, multiple filters may share a @prev node, by way of fork(), which 123 * results in a unidirectional tree existing in memory. This is similar to 124 * how namespaces work. 125 * 126 * seccomp_filter objects should never be modified after being attached 127 * to a task_struct (other than @usage). 128 */ 129 struct seccomp_filter { 130 refcount_t usage; 131 bool log; 132 struct seccomp_filter *prev; 133 struct bpf_prog *prog; 134 struct notification *notif; 135 struct mutex notify_lock; 136 }; 137 138 /* Limit any path through the tree to 256KB worth of instructions. */ 139 #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) 140 141 /* 142 * Endianness is explicitly ignored and left for BPF program authors to manage 143 * as per the specific architecture. 144 */ 145 static void populate_seccomp_data(struct seccomp_data *sd) 146 { 147 struct task_struct *task = current; 148 struct pt_regs *regs = task_pt_regs(task); 149 unsigned long args[6]; 150 151 sd->nr = syscall_get_nr(task, regs); 152 sd->arch = syscall_get_arch(task); 153 syscall_get_arguments(task, regs, args); 154 sd->args[0] = args[0]; 155 sd->args[1] = args[1]; 156 sd->args[2] = args[2]; 157 sd->args[3] = args[3]; 158 sd->args[4] = args[4]; 159 sd->args[5] = args[5]; 160 sd->instruction_pointer = KSTK_EIP(task); 161 } 162 163 /** 164 * seccomp_check_filter - verify seccomp filter code 165 * @filter: filter to verify 166 * @flen: length of filter 167 * 168 * Takes a previously checked filter (by bpf_check_classic) and 169 * redirects all filter code that loads struct sk_buff data 170 * and related data through seccomp_bpf_load. It also 171 * enforces length and alignment checking of those loads. 172 * 173 * Returns 0 if the rule set is legal or -EINVAL if not. 174 */ 175 static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) 176 { 177 int pc; 178 for (pc = 0; pc < flen; pc++) { 179 struct sock_filter *ftest = &filter[pc]; 180 u16 code = ftest->code; 181 u32 k = ftest->k; 182 183 switch (code) { 184 case BPF_LD | BPF_W | BPF_ABS: 185 ftest->code = BPF_LDX | BPF_W | BPF_ABS; 186 /* 32-bit aligned and not out of bounds. */ 187 if (k >= sizeof(struct seccomp_data) || k & 3) 188 return -EINVAL; 189 continue; 190 case BPF_LD | BPF_W | BPF_LEN: 191 ftest->code = BPF_LD | BPF_IMM; 192 ftest->k = sizeof(struct seccomp_data); 193 continue; 194 case BPF_LDX | BPF_W | BPF_LEN: 195 ftest->code = BPF_LDX | BPF_IMM; 196 ftest->k = sizeof(struct seccomp_data); 197 continue; 198 /* Explicitly include allowed calls. */ 199 case BPF_RET | BPF_K: 200 case BPF_RET | BPF_A: 201 case BPF_ALU | BPF_ADD | BPF_K: 202 case BPF_ALU | BPF_ADD | BPF_X: 203 case BPF_ALU | BPF_SUB | BPF_K: 204 case BPF_ALU | BPF_SUB | BPF_X: 205 case BPF_ALU | BPF_MUL | BPF_K: 206 case BPF_ALU | BPF_MUL | BPF_X: 207 case BPF_ALU | BPF_DIV | BPF_K: 208 case BPF_ALU | BPF_DIV | BPF_X: 209 case BPF_ALU | BPF_AND | BPF_K: 210 case BPF_ALU | BPF_AND | BPF_X: 211 case BPF_ALU | BPF_OR | BPF_K: 212 case BPF_ALU | BPF_OR | BPF_X: 213 case BPF_ALU | BPF_XOR | BPF_K: 214 case BPF_ALU | BPF_XOR | BPF_X: 215 case BPF_ALU | BPF_LSH | BPF_K: 216 case BPF_ALU | BPF_LSH | BPF_X: 217 case BPF_ALU | BPF_RSH | BPF_K: 218 case BPF_ALU | BPF_RSH | BPF_X: 219 case BPF_ALU | BPF_NEG: 220 case BPF_LD | BPF_IMM: 221 case BPF_LDX | BPF_IMM: 222 case BPF_MISC | BPF_TAX: 223 case BPF_MISC | BPF_TXA: 224 case BPF_LD | BPF_MEM: 225 case BPF_LDX | BPF_MEM: 226 case BPF_ST: 227 case BPF_STX: 228 case BPF_JMP | BPF_JA: 229 case BPF_JMP | BPF_JEQ | BPF_K: 230 case BPF_JMP | BPF_JEQ | BPF_X: 231 case BPF_JMP | BPF_JGE | BPF_K: 232 case BPF_JMP | BPF_JGE | BPF_X: 233 case BPF_JMP | BPF_JGT | BPF_K: 234 case BPF_JMP | BPF_JGT | BPF_X: 235 case BPF_JMP | BPF_JSET | BPF_K: 236 case BPF_JMP | BPF_JSET | BPF_X: 237 continue; 238 default: 239 return -EINVAL; 240 } 241 } 242 return 0; 243 } 244 245 /** 246 * seccomp_run_filters - evaluates all seccomp filters against @sd 247 * @sd: optional seccomp data to be passed to filters 248 * @match: stores struct seccomp_filter that resulted in the return value, 249 * unless filter returned SECCOMP_RET_ALLOW, in which case it will 250 * be unchanged. 251 * 252 * Returns valid seccomp BPF response codes. 253 */ 254 #define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL))) 255 static u32 seccomp_run_filters(const struct seccomp_data *sd, 256 struct seccomp_filter **match) 257 { 258 u32 ret = SECCOMP_RET_ALLOW; 259 /* Make sure cross-thread synced filter points somewhere sane. */ 260 struct seccomp_filter *f = 261 READ_ONCE(current->seccomp.filter); 262 263 /* Ensure unexpected behavior doesn't result in failing open. */ 264 if (WARN_ON(f == NULL)) 265 return SECCOMP_RET_KILL_PROCESS; 266 267 /* 268 * All filters in the list are evaluated and the lowest BPF return 269 * value always takes priority (ignoring the DATA). 270 */ 271 preempt_disable(); 272 for (; f; f = f->prev) { 273 u32 cur_ret = BPF_PROG_RUN(f->prog, sd); 274 275 if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { 276 ret = cur_ret; 277 *match = f; 278 } 279 } 280 preempt_enable(); 281 return ret; 282 } 283 #endif /* CONFIG_SECCOMP_FILTER */ 284 285 static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode) 286 { 287 assert_spin_locked(¤t->sighand->siglock); 288 289 if (current->seccomp.mode && current->seccomp.mode != seccomp_mode) 290 return false; 291 292 return true; 293 } 294 295 void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } 296 297 static inline void seccomp_assign_mode(struct task_struct *task, 298 unsigned long seccomp_mode, 299 unsigned long flags) 300 { 301 assert_spin_locked(&task->sighand->siglock); 302 303 task->seccomp.mode = seccomp_mode; 304 /* 305 * Make sure TIF_SECCOMP cannot be set before the mode (and 306 * filter) is set. 307 */ 308 smp_mb__before_atomic(); 309 /* Assume default seccomp processes want spec flaw mitigation. */ 310 if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) 311 arch_seccomp_spec_mitigate(task); 312 set_tsk_thread_flag(task, TIF_SECCOMP); 313 } 314 315 #ifdef CONFIG_SECCOMP_FILTER 316 /* Returns 1 if the parent is an ancestor of the child. */ 317 static int is_ancestor(struct seccomp_filter *parent, 318 struct seccomp_filter *child) 319 { 320 /* NULL is the root ancestor. */ 321 if (parent == NULL) 322 return 1; 323 for (; child; child = child->prev) 324 if (child == parent) 325 return 1; 326 return 0; 327 } 328 329 /** 330 * seccomp_can_sync_threads: checks if all threads can be synchronized 331 * 332 * Expects sighand and cred_guard_mutex locks to be held. 333 * 334 * Returns 0 on success, -ve on error, or the pid of a thread which was 335 * either not in the correct seccomp mode or did not have an ancestral 336 * seccomp filter. 337 */ 338 static inline pid_t seccomp_can_sync_threads(void) 339 { 340 struct task_struct *thread, *caller; 341 342 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 343 assert_spin_locked(¤t->sighand->siglock); 344 345 /* Validate all threads being eligible for synchronization. */ 346 caller = current; 347 for_each_thread(caller, thread) { 348 pid_t failed; 349 350 /* Skip current, since it is initiating the sync. */ 351 if (thread == caller) 352 continue; 353 354 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED || 355 (thread->seccomp.mode == SECCOMP_MODE_FILTER && 356 is_ancestor(thread->seccomp.filter, 357 caller->seccomp.filter))) 358 continue; 359 360 /* Return the first thread that cannot be synchronized. */ 361 failed = task_pid_vnr(thread); 362 /* If the pid cannot be resolved, then return -ESRCH */ 363 if (WARN_ON(failed == 0)) 364 failed = -ESRCH; 365 return failed; 366 } 367 368 return 0; 369 } 370 371 /** 372 * seccomp_sync_threads: sets all threads to use current's filter 373 * 374 * Expects sighand and cred_guard_mutex locks to be held, and for 375 * seccomp_can_sync_threads() to have returned success already 376 * without dropping the locks. 377 * 378 */ 379 static inline void seccomp_sync_threads(unsigned long flags) 380 { 381 struct task_struct *thread, *caller; 382 383 BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex)); 384 assert_spin_locked(¤t->sighand->siglock); 385 386 /* Synchronize all threads. */ 387 caller = current; 388 for_each_thread(caller, thread) { 389 /* Skip current, since it needs no changes. */ 390 if (thread == caller) 391 continue; 392 393 /* Get a task reference for the new leaf node. */ 394 get_seccomp_filter(caller); 395 /* 396 * Drop the task reference to the shared ancestor since 397 * current's path will hold a reference. (This also 398 * allows a put before the assignment.) 399 */ 400 put_seccomp_filter(thread); 401 smp_store_release(&thread->seccomp.filter, 402 caller->seccomp.filter); 403 404 /* 405 * Don't let an unprivileged task work around 406 * the no_new_privs restriction by creating 407 * a thread that sets it up, enters seccomp, 408 * then dies. 409 */ 410 if (task_no_new_privs(caller)) 411 task_set_no_new_privs(thread); 412 413 /* 414 * Opt the other thread into seccomp if needed. 415 * As threads are considered to be trust-realm 416 * equivalent (see ptrace_may_access), it is safe to 417 * allow one thread to transition the other. 418 */ 419 if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) 420 seccomp_assign_mode(thread, SECCOMP_MODE_FILTER, 421 flags); 422 } 423 } 424 425 /** 426 * seccomp_prepare_filter: Prepares a seccomp filter for use. 427 * @fprog: BPF program to install 428 * 429 * Returns filter on success or an ERR_PTR on failure. 430 */ 431 static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) 432 { 433 struct seccomp_filter *sfilter; 434 int ret; 435 const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); 436 437 if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) 438 return ERR_PTR(-EINVAL); 439 440 BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter)); 441 442 /* 443 * Installing a seccomp filter requires that the task has 444 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs. 445 * This avoids scenarios where unprivileged tasks can affect the 446 * behavior of privileged children. 447 */ 448 if (!task_no_new_privs(current) && 449 security_capable(current_cred(), current_user_ns(), 450 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0) 451 return ERR_PTR(-EACCES); 452 453 /* Allocate a new seccomp_filter */ 454 sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); 455 if (!sfilter) 456 return ERR_PTR(-ENOMEM); 457 458 mutex_init(&sfilter->notify_lock); 459 ret = bpf_prog_create_from_user(&sfilter->prog, fprog, 460 seccomp_check_filter, save_orig); 461 if (ret < 0) { 462 kfree(sfilter); 463 return ERR_PTR(ret); 464 } 465 466 refcount_set(&sfilter->usage, 1); 467 468 return sfilter; 469 } 470 471 /** 472 * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog 473 * @user_filter: pointer to the user data containing a sock_fprog. 474 * 475 * Returns 0 on success and non-zero otherwise. 476 */ 477 static struct seccomp_filter * 478 seccomp_prepare_user_filter(const char __user *user_filter) 479 { 480 struct sock_fprog fprog; 481 struct seccomp_filter *filter = ERR_PTR(-EFAULT); 482 483 #ifdef CONFIG_COMPAT 484 if (in_compat_syscall()) { 485 struct compat_sock_fprog fprog32; 486 if (copy_from_user(&fprog32, user_filter, sizeof(fprog32))) 487 goto out; 488 fprog.len = fprog32.len; 489 fprog.filter = compat_ptr(fprog32.filter); 490 } else /* falls through to the if below. */ 491 #endif 492 if (copy_from_user(&fprog, user_filter, sizeof(fprog))) 493 goto out; 494 filter = seccomp_prepare_filter(&fprog); 495 out: 496 return filter; 497 } 498 499 /** 500 * seccomp_attach_filter: validate and attach filter 501 * @flags: flags to change filter behavior 502 * @filter: seccomp filter to add to the current process 503 * 504 * Caller must be holding current->sighand->siglock lock. 505 * 506 * Returns 0 on success, -ve on error, or 507 * - in TSYNC mode: the pid of a thread which was either not in the correct 508 * seccomp mode or did not have an ancestral seccomp filter 509 * - in NEW_LISTENER mode: the fd of the new listener 510 */ 511 static long seccomp_attach_filter(unsigned int flags, 512 struct seccomp_filter *filter) 513 { 514 unsigned long total_insns; 515 struct seccomp_filter *walker; 516 517 assert_spin_locked(¤t->sighand->siglock); 518 519 /* Validate resulting filter length. */ 520 total_insns = filter->prog->len; 521 for (walker = current->seccomp.filter; walker; walker = walker->prev) 522 total_insns += walker->prog->len + 4; /* 4 instr penalty */ 523 if (total_insns > MAX_INSNS_PER_PATH) 524 return -ENOMEM; 525 526 /* If thread sync has been requested, check that it is possible. */ 527 if (flags & SECCOMP_FILTER_FLAG_TSYNC) { 528 int ret; 529 530 ret = seccomp_can_sync_threads(); 531 if (ret) { 532 if (flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) 533 return -ESRCH; 534 else 535 return ret; 536 } 537 } 538 539 /* Set log flag, if present. */ 540 if (flags & SECCOMP_FILTER_FLAG_LOG) 541 filter->log = true; 542 543 /* 544 * If there is an existing filter, make it the prev and don't drop its 545 * task reference. 546 */ 547 filter->prev = current->seccomp.filter; 548 current->seccomp.filter = filter; 549 550 /* Now that the new filter is in place, synchronize to all threads. */ 551 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 552 seccomp_sync_threads(flags); 553 554 return 0; 555 } 556 557 static void __get_seccomp_filter(struct seccomp_filter *filter) 558 { 559 refcount_inc(&filter->usage); 560 } 561 562 /* get_seccomp_filter - increments the reference count of the filter on @tsk */ 563 void get_seccomp_filter(struct task_struct *tsk) 564 { 565 struct seccomp_filter *orig = tsk->seccomp.filter; 566 if (!orig) 567 return; 568 __get_seccomp_filter(orig); 569 } 570 571 static inline void seccomp_filter_free(struct seccomp_filter *filter) 572 { 573 if (filter) { 574 bpf_prog_destroy(filter->prog); 575 kfree(filter); 576 } 577 } 578 579 static void __put_seccomp_filter(struct seccomp_filter *orig) 580 { 581 /* Clean up single-reference branches iteratively. */ 582 while (orig && refcount_dec_and_test(&orig->usage)) { 583 struct seccomp_filter *freeme = orig; 584 orig = orig->prev; 585 seccomp_filter_free(freeme); 586 } 587 } 588 589 /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ 590 void put_seccomp_filter(struct task_struct *tsk) 591 { 592 __put_seccomp_filter(tsk->seccomp.filter); 593 } 594 595 static void seccomp_init_siginfo(kernel_siginfo_t *info, int syscall, int reason) 596 { 597 clear_siginfo(info); 598 info->si_signo = SIGSYS; 599 info->si_code = SYS_SECCOMP; 600 info->si_call_addr = (void __user *)KSTK_EIP(current); 601 info->si_errno = reason; 602 info->si_arch = syscall_get_arch(current); 603 info->si_syscall = syscall; 604 } 605 606 /** 607 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation 608 * @syscall: syscall number to send to userland 609 * @reason: filter-supplied reason code to send to userland (via si_errno) 610 * 611 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. 612 */ 613 static void seccomp_send_sigsys(int syscall, int reason) 614 { 615 struct kernel_siginfo info; 616 seccomp_init_siginfo(&info, syscall, reason); 617 force_sig_info(&info); 618 } 619 #endif /* CONFIG_SECCOMP_FILTER */ 620 621 /* For use with seccomp_actions_logged */ 622 #define SECCOMP_LOG_KILL_PROCESS (1 << 0) 623 #define SECCOMP_LOG_KILL_THREAD (1 << 1) 624 #define SECCOMP_LOG_TRAP (1 << 2) 625 #define SECCOMP_LOG_ERRNO (1 << 3) 626 #define SECCOMP_LOG_TRACE (1 << 4) 627 #define SECCOMP_LOG_LOG (1 << 5) 628 #define SECCOMP_LOG_ALLOW (1 << 6) 629 #define SECCOMP_LOG_USER_NOTIF (1 << 7) 630 631 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | 632 SECCOMP_LOG_KILL_THREAD | 633 SECCOMP_LOG_TRAP | 634 SECCOMP_LOG_ERRNO | 635 SECCOMP_LOG_USER_NOTIF | 636 SECCOMP_LOG_TRACE | 637 SECCOMP_LOG_LOG; 638 639 static inline void seccomp_log(unsigned long syscall, long signr, u32 action, 640 bool requested) 641 { 642 bool log = false; 643 644 switch (action) { 645 case SECCOMP_RET_ALLOW: 646 break; 647 case SECCOMP_RET_TRAP: 648 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; 649 break; 650 case SECCOMP_RET_ERRNO: 651 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; 652 break; 653 case SECCOMP_RET_TRACE: 654 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; 655 break; 656 case SECCOMP_RET_USER_NOTIF: 657 log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF; 658 break; 659 case SECCOMP_RET_LOG: 660 log = seccomp_actions_logged & SECCOMP_LOG_LOG; 661 break; 662 case SECCOMP_RET_KILL_THREAD: 663 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; 664 break; 665 case SECCOMP_RET_KILL_PROCESS: 666 default: 667 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; 668 } 669 670 /* 671 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the 672 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence 673 * any action from being logged by removing the action name from the 674 * seccomp_actions_logged sysctl. 675 */ 676 if (!log) 677 return; 678 679 audit_seccomp(syscall, signr, action); 680 } 681 682 /* 683 * Secure computing mode 1 allows only read/write/exit/sigreturn. 684 * To be fully secure this must be combined with rlimit 685 * to limit the stack allocations too. 686 */ 687 static const int mode1_syscalls[] = { 688 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, 689 0, /* null terminated */ 690 }; 691 692 static void __secure_computing_strict(int this_syscall) 693 { 694 const int *syscall_whitelist = mode1_syscalls; 695 #ifdef CONFIG_COMPAT 696 if (in_compat_syscall()) 697 syscall_whitelist = get_compat_mode1_syscalls(); 698 #endif 699 do { 700 if (*syscall_whitelist == this_syscall) 701 return; 702 } while (*++syscall_whitelist); 703 704 #ifdef SECCOMP_DEBUG 705 dump_stack(); 706 #endif 707 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); 708 do_exit(SIGKILL); 709 } 710 711 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER 712 void secure_computing_strict(int this_syscall) 713 { 714 int mode = current->seccomp.mode; 715 716 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 717 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 718 return; 719 720 if (mode == SECCOMP_MODE_DISABLED) 721 return; 722 else if (mode == SECCOMP_MODE_STRICT) 723 __secure_computing_strict(this_syscall); 724 else 725 BUG(); 726 } 727 #else 728 729 #ifdef CONFIG_SECCOMP_FILTER 730 static u64 seccomp_next_notify_id(struct seccomp_filter *filter) 731 { 732 /* 733 * Note: overflow is ok here, the id just needs to be unique per 734 * filter. 735 */ 736 lockdep_assert_held(&filter->notify_lock); 737 return filter->notif->next_id++; 738 } 739 740 static int seccomp_do_user_notification(int this_syscall, 741 struct seccomp_filter *match, 742 const struct seccomp_data *sd) 743 { 744 int err; 745 u32 flags = 0; 746 long ret = 0; 747 struct seccomp_knotif n = {}; 748 749 mutex_lock(&match->notify_lock); 750 err = -ENOSYS; 751 if (!match->notif) 752 goto out; 753 754 n.task = current; 755 n.state = SECCOMP_NOTIFY_INIT; 756 n.data = sd; 757 n.id = seccomp_next_notify_id(match); 758 init_completion(&n.ready); 759 list_add(&n.list, &match->notif->notifications); 760 761 up(&match->notif->request); 762 wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM); 763 mutex_unlock(&match->notify_lock); 764 765 /* 766 * This is where we wait for a reply from userspace. 767 */ 768 err = wait_for_completion_interruptible(&n.ready); 769 mutex_lock(&match->notify_lock); 770 if (err == 0) { 771 ret = n.val; 772 err = n.error; 773 flags = n.flags; 774 } 775 776 /* 777 * Note that it's possible the listener died in between the time when 778 * we were notified of a respons (or a signal) and when we were able to 779 * re-acquire the lock, so only delete from the list if the 780 * notification actually exists. 781 * 782 * Also note that this test is only valid because there's no way to 783 * *reattach* to a notifier right now. If one is added, we'll need to 784 * keep track of the notif itself and make sure they match here. 785 */ 786 if (match->notif) 787 list_del(&n.list); 788 out: 789 mutex_unlock(&match->notify_lock); 790 791 /* Userspace requests to continue the syscall. */ 792 if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) 793 return 0; 794 795 syscall_set_return_value(current, task_pt_regs(current), 796 err, ret); 797 return -1; 798 } 799 800 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 801 const bool recheck_after_trace) 802 { 803 u32 filter_ret, action; 804 struct seccomp_filter *match = NULL; 805 int data; 806 struct seccomp_data sd_local; 807 808 /* 809 * Make sure that any changes to mode from another thread have 810 * been seen after TIF_SECCOMP was seen. 811 */ 812 rmb(); 813 814 if (!sd) { 815 populate_seccomp_data(&sd_local); 816 sd = &sd_local; 817 } 818 819 filter_ret = seccomp_run_filters(sd, &match); 820 data = filter_ret & SECCOMP_RET_DATA; 821 action = filter_ret & SECCOMP_RET_ACTION_FULL; 822 823 switch (action) { 824 case SECCOMP_RET_ERRNO: 825 /* Set low-order bits as an errno, capped at MAX_ERRNO. */ 826 if (data > MAX_ERRNO) 827 data = MAX_ERRNO; 828 syscall_set_return_value(current, task_pt_regs(current), 829 -data, 0); 830 goto skip; 831 832 case SECCOMP_RET_TRAP: 833 /* Show the handler the original registers. */ 834 syscall_rollback(current, task_pt_regs(current)); 835 /* Let the filter pass back 16 bits of data. */ 836 seccomp_send_sigsys(this_syscall, data); 837 goto skip; 838 839 case SECCOMP_RET_TRACE: 840 /* We've been put in this state by the ptracer already. */ 841 if (recheck_after_trace) 842 return 0; 843 844 /* ENOSYS these calls if there is no tracer attached. */ 845 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { 846 syscall_set_return_value(current, 847 task_pt_regs(current), 848 -ENOSYS, 0); 849 goto skip; 850 } 851 852 /* Allow the BPF to provide the event message */ 853 ptrace_event(PTRACE_EVENT_SECCOMP, data); 854 /* 855 * The delivery of a fatal signal during event 856 * notification may silently skip tracer notification, 857 * which could leave us with a potentially unmodified 858 * syscall that the tracer would have liked to have 859 * changed. Since the process is about to die, we just 860 * force the syscall to be skipped and let the signal 861 * kill the process and correctly handle any tracer exit 862 * notifications. 863 */ 864 if (fatal_signal_pending(current)) 865 goto skip; 866 /* Check if the tracer forced the syscall to be skipped. */ 867 this_syscall = syscall_get_nr(current, task_pt_regs(current)); 868 if (this_syscall < 0) 869 goto skip; 870 871 /* 872 * Recheck the syscall, since it may have changed. This 873 * intentionally uses a NULL struct seccomp_data to force 874 * a reload of all registers. This does not goto skip since 875 * a skip would have already been reported. 876 */ 877 if (__seccomp_filter(this_syscall, NULL, true)) 878 return -1; 879 880 return 0; 881 882 case SECCOMP_RET_USER_NOTIF: 883 if (seccomp_do_user_notification(this_syscall, match, sd)) 884 goto skip; 885 886 return 0; 887 888 case SECCOMP_RET_LOG: 889 seccomp_log(this_syscall, 0, action, true); 890 return 0; 891 892 case SECCOMP_RET_ALLOW: 893 /* 894 * Note that the "match" filter will always be NULL for 895 * this action since SECCOMP_RET_ALLOW is the starting 896 * state in seccomp_run_filters(). 897 */ 898 return 0; 899 900 case SECCOMP_RET_KILL_THREAD: 901 case SECCOMP_RET_KILL_PROCESS: 902 default: 903 seccomp_log(this_syscall, SIGSYS, action, true); 904 /* Dump core only if this is the last remaining thread. */ 905 if (action == SECCOMP_RET_KILL_PROCESS || 906 get_nr_threads(current) == 1) { 907 kernel_siginfo_t info; 908 909 /* Show the original registers in the dump. */ 910 syscall_rollback(current, task_pt_regs(current)); 911 /* Trigger a manual coredump since do_exit skips it. */ 912 seccomp_init_siginfo(&info, this_syscall, data); 913 do_coredump(&info); 914 } 915 if (action == SECCOMP_RET_KILL_PROCESS) 916 do_group_exit(SIGSYS); 917 else 918 do_exit(SIGSYS); 919 } 920 921 unreachable(); 922 923 skip: 924 seccomp_log(this_syscall, 0, action, match ? match->log : false); 925 return -1; 926 } 927 #else 928 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 929 const bool recheck_after_trace) 930 { 931 BUG(); 932 } 933 #endif 934 935 int __secure_computing(const struct seccomp_data *sd) 936 { 937 int mode = current->seccomp.mode; 938 int this_syscall; 939 940 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 941 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 942 return 0; 943 944 this_syscall = sd ? sd->nr : 945 syscall_get_nr(current, task_pt_regs(current)); 946 947 switch (mode) { 948 case SECCOMP_MODE_STRICT: 949 __secure_computing_strict(this_syscall); /* may call do_exit */ 950 return 0; 951 case SECCOMP_MODE_FILTER: 952 return __seccomp_filter(this_syscall, sd, false); 953 default: 954 BUG(); 955 } 956 } 957 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ 958 959 long prctl_get_seccomp(void) 960 { 961 return current->seccomp.mode; 962 } 963 964 /** 965 * seccomp_set_mode_strict: internal function for setting strict seccomp 966 * 967 * Once current->seccomp.mode is non-zero, it may not be changed. 968 * 969 * Returns 0 on success or -EINVAL on failure. 970 */ 971 static long seccomp_set_mode_strict(void) 972 { 973 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; 974 long ret = -EINVAL; 975 976 spin_lock_irq(¤t->sighand->siglock); 977 978 if (!seccomp_may_assign_mode(seccomp_mode)) 979 goto out; 980 981 #ifdef TIF_NOTSC 982 disable_TSC(); 983 #endif 984 seccomp_assign_mode(current, seccomp_mode, 0); 985 ret = 0; 986 987 out: 988 spin_unlock_irq(¤t->sighand->siglock); 989 990 return ret; 991 } 992 993 #ifdef CONFIG_SECCOMP_FILTER 994 static int seccomp_notify_release(struct inode *inode, struct file *file) 995 { 996 struct seccomp_filter *filter = file->private_data; 997 struct seccomp_knotif *knotif; 998 999 if (!filter) 1000 return 0; 1001 1002 mutex_lock(&filter->notify_lock); 1003 1004 /* 1005 * If this file is being closed because e.g. the task who owned it 1006 * died, let's wake everyone up who was waiting on us. 1007 */ 1008 list_for_each_entry(knotif, &filter->notif->notifications, list) { 1009 if (knotif->state == SECCOMP_NOTIFY_REPLIED) 1010 continue; 1011 1012 knotif->state = SECCOMP_NOTIFY_REPLIED; 1013 knotif->error = -ENOSYS; 1014 knotif->val = 0; 1015 1016 complete(&knotif->ready); 1017 } 1018 1019 kfree(filter->notif); 1020 filter->notif = NULL; 1021 mutex_unlock(&filter->notify_lock); 1022 __put_seccomp_filter(filter); 1023 return 0; 1024 } 1025 1026 static long seccomp_notify_recv(struct seccomp_filter *filter, 1027 void __user *buf) 1028 { 1029 struct seccomp_knotif *knotif = NULL, *cur; 1030 struct seccomp_notif unotif; 1031 ssize_t ret; 1032 1033 /* Verify that we're not given garbage to keep struct extensible. */ 1034 ret = check_zeroed_user(buf, sizeof(unotif)); 1035 if (ret < 0) 1036 return ret; 1037 if (!ret) 1038 return -EINVAL; 1039 1040 memset(&unotif, 0, sizeof(unotif)); 1041 1042 ret = down_interruptible(&filter->notif->request); 1043 if (ret < 0) 1044 return ret; 1045 1046 mutex_lock(&filter->notify_lock); 1047 list_for_each_entry(cur, &filter->notif->notifications, list) { 1048 if (cur->state == SECCOMP_NOTIFY_INIT) { 1049 knotif = cur; 1050 break; 1051 } 1052 } 1053 1054 /* 1055 * If we didn't find a notification, it could be that the task was 1056 * interrupted by a fatal signal between the time we were woken and 1057 * when we were able to acquire the rw lock. 1058 */ 1059 if (!knotif) { 1060 ret = -ENOENT; 1061 goto out; 1062 } 1063 1064 unotif.id = knotif->id; 1065 unotif.pid = task_pid_vnr(knotif->task); 1066 unotif.data = *(knotif->data); 1067 1068 knotif->state = SECCOMP_NOTIFY_SENT; 1069 wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM); 1070 ret = 0; 1071 out: 1072 mutex_unlock(&filter->notify_lock); 1073 1074 if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) { 1075 ret = -EFAULT; 1076 1077 /* 1078 * Userspace screwed up. To make sure that we keep this 1079 * notification alive, let's reset it back to INIT. It 1080 * may have died when we released the lock, so we need to make 1081 * sure it's still around. 1082 */ 1083 knotif = NULL; 1084 mutex_lock(&filter->notify_lock); 1085 list_for_each_entry(cur, &filter->notif->notifications, list) { 1086 if (cur->id == unotif.id) { 1087 knotif = cur; 1088 break; 1089 } 1090 } 1091 1092 if (knotif) { 1093 knotif->state = SECCOMP_NOTIFY_INIT; 1094 up(&filter->notif->request); 1095 } 1096 mutex_unlock(&filter->notify_lock); 1097 } 1098 1099 return ret; 1100 } 1101 1102 static long seccomp_notify_send(struct seccomp_filter *filter, 1103 void __user *buf) 1104 { 1105 struct seccomp_notif_resp resp = {}; 1106 struct seccomp_knotif *knotif = NULL, *cur; 1107 long ret; 1108 1109 if (copy_from_user(&resp, buf, sizeof(resp))) 1110 return -EFAULT; 1111 1112 if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE) 1113 return -EINVAL; 1114 1115 if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) && 1116 (resp.error || resp.val)) 1117 return -EINVAL; 1118 1119 ret = mutex_lock_interruptible(&filter->notify_lock); 1120 if (ret < 0) 1121 return ret; 1122 1123 list_for_each_entry(cur, &filter->notif->notifications, list) { 1124 if (cur->id == resp.id) { 1125 knotif = cur; 1126 break; 1127 } 1128 } 1129 1130 if (!knotif) { 1131 ret = -ENOENT; 1132 goto out; 1133 } 1134 1135 /* Allow exactly one reply. */ 1136 if (knotif->state != SECCOMP_NOTIFY_SENT) { 1137 ret = -EINPROGRESS; 1138 goto out; 1139 } 1140 1141 ret = 0; 1142 knotif->state = SECCOMP_NOTIFY_REPLIED; 1143 knotif->error = resp.error; 1144 knotif->val = resp.val; 1145 knotif->flags = resp.flags; 1146 complete(&knotif->ready); 1147 out: 1148 mutex_unlock(&filter->notify_lock); 1149 return ret; 1150 } 1151 1152 static long seccomp_notify_id_valid(struct seccomp_filter *filter, 1153 void __user *buf) 1154 { 1155 struct seccomp_knotif *knotif = NULL; 1156 u64 id; 1157 long ret; 1158 1159 if (copy_from_user(&id, buf, sizeof(id))) 1160 return -EFAULT; 1161 1162 ret = mutex_lock_interruptible(&filter->notify_lock); 1163 if (ret < 0) 1164 return ret; 1165 1166 ret = -ENOENT; 1167 list_for_each_entry(knotif, &filter->notif->notifications, list) { 1168 if (knotif->id == id) { 1169 if (knotif->state == SECCOMP_NOTIFY_SENT) 1170 ret = 0; 1171 goto out; 1172 } 1173 } 1174 1175 out: 1176 mutex_unlock(&filter->notify_lock); 1177 return ret; 1178 } 1179 1180 static long seccomp_notify_ioctl(struct file *file, unsigned int cmd, 1181 unsigned long arg) 1182 { 1183 struct seccomp_filter *filter = file->private_data; 1184 void __user *buf = (void __user *)arg; 1185 1186 switch (cmd) { 1187 case SECCOMP_IOCTL_NOTIF_RECV: 1188 return seccomp_notify_recv(filter, buf); 1189 case SECCOMP_IOCTL_NOTIF_SEND: 1190 return seccomp_notify_send(filter, buf); 1191 case SECCOMP_IOCTL_NOTIF_ID_VALID: 1192 return seccomp_notify_id_valid(filter, buf); 1193 default: 1194 return -EINVAL; 1195 } 1196 } 1197 1198 static __poll_t seccomp_notify_poll(struct file *file, 1199 struct poll_table_struct *poll_tab) 1200 { 1201 struct seccomp_filter *filter = file->private_data; 1202 __poll_t ret = 0; 1203 struct seccomp_knotif *cur; 1204 1205 poll_wait(file, &filter->notif->wqh, poll_tab); 1206 1207 if (mutex_lock_interruptible(&filter->notify_lock) < 0) 1208 return EPOLLERR; 1209 1210 list_for_each_entry(cur, &filter->notif->notifications, list) { 1211 if (cur->state == SECCOMP_NOTIFY_INIT) 1212 ret |= EPOLLIN | EPOLLRDNORM; 1213 if (cur->state == SECCOMP_NOTIFY_SENT) 1214 ret |= EPOLLOUT | EPOLLWRNORM; 1215 if ((ret & EPOLLIN) && (ret & EPOLLOUT)) 1216 break; 1217 } 1218 1219 mutex_unlock(&filter->notify_lock); 1220 1221 return ret; 1222 } 1223 1224 static const struct file_operations seccomp_notify_ops = { 1225 .poll = seccomp_notify_poll, 1226 .release = seccomp_notify_release, 1227 .unlocked_ioctl = seccomp_notify_ioctl, 1228 .compat_ioctl = seccomp_notify_ioctl, 1229 }; 1230 1231 static struct file *init_listener(struct seccomp_filter *filter) 1232 { 1233 struct file *ret = ERR_PTR(-EBUSY); 1234 struct seccomp_filter *cur; 1235 1236 for (cur = current->seccomp.filter; cur; cur = cur->prev) { 1237 if (cur->notif) 1238 goto out; 1239 } 1240 1241 ret = ERR_PTR(-ENOMEM); 1242 filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); 1243 if (!filter->notif) 1244 goto out; 1245 1246 sema_init(&filter->notif->request, 0); 1247 filter->notif->next_id = get_random_u64(); 1248 INIT_LIST_HEAD(&filter->notif->notifications); 1249 init_waitqueue_head(&filter->notif->wqh); 1250 1251 ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, 1252 filter, O_RDWR); 1253 if (IS_ERR(ret)) 1254 goto out_notif; 1255 1256 /* The file has a reference to it now */ 1257 __get_seccomp_filter(filter); 1258 1259 out_notif: 1260 if (IS_ERR(ret)) 1261 kfree(filter->notif); 1262 out: 1263 return ret; 1264 } 1265 1266 /** 1267 * seccomp_set_mode_filter: internal function for setting seccomp filter 1268 * @flags: flags to change filter behavior 1269 * @filter: struct sock_fprog containing filter 1270 * 1271 * This function may be called repeatedly to install additional filters. 1272 * Every filter successfully installed will be evaluated (in reverse order) 1273 * for each system call the task makes. 1274 * 1275 * Once current->seccomp.mode is non-zero, it may not be changed. 1276 * 1277 * Returns 0 on success or -EINVAL on failure. 1278 */ 1279 static long seccomp_set_mode_filter(unsigned int flags, 1280 const char __user *filter) 1281 { 1282 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; 1283 struct seccomp_filter *prepared = NULL; 1284 long ret = -EINVAL; 1285 int listener = -1; 1286 struct file *listener_f = NULL; 1287 1288 /* Validate flags. */ 1289 if (flags & ~SECCOMP_FILTER_FLAG_MASK) 1290 return -EINVAL; 1291 1292 /* 1293 * In the successful case, NEW_LISTENER returns the new listener fd. 1294 * But in the failure case, TSYNC returns the thread that died. If you 1295 * combine these two flags, there's no way to tell whether something 1296 * succeeded or failed. So, let's disallow this combination if the user 1297 * has not explicitly requested no errors from TSYNC. 1298 */ 1299 if ((flags & SECCOMP_FILTER_FLAG_TSYNC) && 1300 (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) && 1301 ((flags & SECCOMP_FILTER_FLAG_TSYNC_ESRCH) == 0)) 1302 return -EINVAL; 1303 1304 /* Prepare the new filter before holding any locks. */ 1305 prepared = seccomp_prepare_user_filter(filter); 1306 if (IS_ERR(prepared)) 1307 return PTR_ERR(prepared); 1308 1309 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 1310 listener = get_unused_fd_flags(O_CLOEXEC); 1311 if (listener < 0) { 1312 ret = listener; 1313 goto out_free; 1314 } 1315 1316 listener_f = init_listener(prepared); 1317 if (IS_ERR(listener_f)) { 1318 put_unused_fd(listener); 1319 ret = PTR_ERR(listener_f); 1320 goto out_free; 1321 } 1322 } 1323 1324 /* 1325 * Make sure we cannot change seccomp or nnp state via TSYNC 1326 * while another thread is in the middle of calling exec. 1327 */ 1328 if (flags & SECCOMP_FILTER_FLAG_TSYNC && 1329 mutex_lock_killable(¤t->signal->cred_guard_mutex)) 1330 goto out_put_fd; 1331 1332 spin_lock_irq(¤t->sighand->siglock); 1333 1334 if (!seccomp_may_assign_mode(seccomp_mode)) 1335 goto out; 1336 1337 ret = seccomp_attach_filter(flags, prepared); 1338 if (ret) 1339 goto out; 1340 /* Do not free the successfully attached filter. */ 1341 prepared = NULL; 1342 1343 seccomp_assign_mode(current, seccomp_mode, flags); 1344 out: 1345 spin_unlock_irq(¤t->sighand->siglock); 1346 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 1347 mutex_unlock(¤t->signal->cred_guard_mutex); 1348 out_put_fd: 1349 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 1350 if (ret) { 1351 listener_f->private_data = NULL; 1352 fput(listener_f); 1353 put_unused_fd(listener); 1354 } else { 1355 fd_install(listener, listener_f); 1356 ret = listener; 1357 } 1358 } 1359 out_free: 1360 seccomp_filter_free(prepared); 1361 return ret; 1362 } 1363 #else 1364 static inline long seccomp_set_mode_filter(unsigned int flags, 1365 const char __user *filter) 1366 { 1367 return -EINVAL; 1368 } 1369 #endif 1370 1371 static long seccomp_get_action_avail(const char __user *uaction) 1372 { 1373 u32 action; 1374 1375 if (copy_from_user(&action, uaction, sizeof(action))) 1376 return -EFAULT; 1377 1378 switch (action) { 1379 case SECCOMP_RET_KILL_PROCESS: 1380 case SECCOMP_RET_KILL_THREAD: 1381 case SECCOMP_RET_TRAP: 1382 case SECCOMP_RET_ERRNO: 1383 case SECCOMP_RET_USER_NOTIF: 1384 case SECCOMP_RET_TRACE: 1385 case SECCOMP_RET_LOG: 1386 case SECCOMP_RET_ALLOW: 1387 break; 1388 default: 1389 return -EOPNOTSUPP; 1390 } 1391 1392 return 0; 1393 } 1394 1395 static long seccomp_get_notif_sizes(void __user *usizes) 1396 { 1397 struct seccomp_notif_sizes sizes = { 1398 .seccomp_notif = sizeof(struct seccomp_notif), 1399 .seccomp_notif_resp = sizeof(struct seccomp_notif_resp), 1400 .seccomp_data = sizeof(struct seccomp_data), 1401 }; 1402 1403 if (copy_to_user(usizes, &sizes, sizeof(sizes))) 1404 return -EFAULT; 1405 1406 return 0; 1407 } 1408 1409 /* Common entry point for both prctl and syscall. */ 1410 static long do_seccomp(unsigned int op, unsigned int flags, 1411 void __user *uargs) 1412 { 1413 switch (op) { 1414 case SECCOMP_SET_MODE_STRICT: 1415 if (flags != 0 || uargs != NULL) 1416 return -EINVAL; 1417 return seccomp_set_mode_strict(); 1418 case SECCOMP_SET_MODE_FILTER: 1419 return seccomp_set_mode_filter(flags, uargs); 1420 case SECCOMP_GET_ACTION_AVAIL: 1421 if (flags != 0) 1422 return -EINVAL; 1423 1424 return seccomp_get_action_avail(uargs); 1425 case SECCOMP_GET_NOTIF_SIZES: 1426 if (flags != 0) 1427 return -EINVAL; 1428 1429 return seccomp_get_notif_sizes(uargs); 1430 default: 1431 return -EINVAL; 1432 } 1433 } 1434 1435 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, 1436 void __user *, uargs) 1437 { 1438 return do_seccomp(op, flags, uargs); 1439 } 1440 1441 /** 1442 * prctl_set_seccomp: configures current->seccomp.mode 1443 * @seccomp_mode: requested mode to use 1444 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER 1445 * 1446 * Returns 0 on success or -EINVAL on failure. 1447 */ 1448 long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter) 1449 { 1450 unsigned int op; 1451 void __user *uargs; 1452 1453 switch (seccomp_mode) { 1454 case SECCOMP_MODE_STRICT: 1455 op = SECCOMP_SET_MODE_STRICT; 1456 /* 1457 * Setting strict mode through prctl always ignored filter, 1458 * so make sure it is always NULL here to pass the internal 1459 * check in do_seccomp(). 1460 */ 1461 uargs = NULL; 1462 break; 1463 case SECCOMP_MODE_FILTER: 1464 op = SECCOMP_SET_MODE_FILTER; 1465 uargs = filter; 1466 break; 1467 default: 1468 return -EINVAL; 1469 } 1470 1471 /* prctl interface doesn't have flags, so they are always zero. */ 1472 return do_seccomp(op, 0, uargs); 1473 } 1474 1475 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) 1476 static struct seccomp_filter *get_nth_filter(struct task_struct *task, 1477 unsigned long filter_off) 1478 { 1479 struct seccomp_filter *orig, *filter; 1480 unsigned long count; 1481 1482 /* 1483 * Note: this is only correct because the caller should be the (ptrace) 1484 * tracer of the task, otherwise lock_task_sighand is needed. 1485 */ 1486 spin_lock_irq(&task->sighand->siglock); 1487 1488 if (task->seccomp.mode != SECCOMP_MODE_FILTER) { 1489 spin_unlock_irq(&task->sighand->siglock); 1490 return ERR_PTR(-EINVAL); 1491 } 1492 1493 orig = task->seccomp.filter; 1494 __get_seccomp_filter(orig); 1495 spin_unlock_irq(&task->sighand->siglock); 1496 1497 count = 0; 1498 for (filter = orig; filter; filter = filter->prev) 1499 count++; 1500 1501 if (filter_off >= count) { 1502 filter = ERR_PTR(-ENOENT); 1503 goto out; 1504 } 1505 1506 count -= filter_off; 1507 for (filter = orig; filter && count > 1; filter = filter->prev) 1508 count--; 1509 1510 if (WARN_ON(count != 1 || !filter)) { 1511 filter = ERR_PTR(-ENOENT); 1512 goto out; 1513 } 1514 1515 __get_seccomp_filter(filter); 1516 1517 out: 1518 __put_seccomp_filter(orig); 1519 return filter; 1520 } 1521 1522 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, 1523 void __user *data) 1524 { 1525 struct seccomp_filter *filter; 1526 struct sock_fprog_kern *fprog; 1527 long ret; 1528 1529 if (!capable(CAP_SYS_ADMIN) || 1530 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1531 return -EACCES; 1532 } 1533 1534 filter = get_nth_filter(task, filter_off); 1535 if (IS_ERR(filter)) 1536 return PTR_ERR(filter); 1537 1538 fprog = filter->prog->orig_prog; 1539 if (!fprog) { 1540 /* This must be a new non-cBPF filter, since we save 1541 * every cBPF filter's orig_prog above when 1542 * CONFIG_CHECKPOINT_RESTORE is enabled. 1543 */ 1544 ret = -EMEDIUMTYPE; 1545 goto out; 1546 } 1547 1548 ret = fprog->len; 1549 if (!data) 1550 goto out; 1551 1552 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) 1553 ret = -EFAULT; 1554 1555 out: 1556 __put_seccomp_filter(filter); 1557 return ret; 1558 } 1559 1560 long seccomp_get_metadata(struct task_struct *task, 1561 unsigned long size, void __user *data) 1562 { 1563 long ret; 1564 struct seccomp_filter *filter; 1565 struct seccomp_metadata kmd = {}; 1566 1567 if (!capable(CAP_SYS_ADMIN) || 1568 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1569 return -EACCES; 1570 } 1571 1572 size = min_t(unsigned long, size, sizeof(kmd)); 1573 1574 if (size < sizeof(kmd.filter_off)) 1575 return -EINVAL; 1576 1577 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) 1578 return -EFAULT; 1579 1580 filter = get_nth_filter(task, kmd.filter_off); 1581 if (IS_ERR(filter)) 1582 return PTR_ERR(filter); 1583 1584 if (filter->log) 1585 kmd.flags |= SECCOMP_FILTER_FLAG_LOG; 1586 1587 ret = size; 1588 if (copy_to_user(data, &kmd, size)) 1589 ret = -EFAULT; 1590 1591 __put_seccomp_filter(filter); 1592 return ret; 1593 } 1594 #endif 1595 1596 #ifdef CONFIG_SYSCTL 1597 1598 /* Human readable action names for friendly sysctl interaction */ 1599 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" 1600 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" 1601 #define SECCOMP_RET_TRAP_NAME "trap" 1602 #define SECCOMP_RET_ERRNO_NAME "errno" 1603 #define SECCOMP_RET_USER_NOTIF_NAME "user_notif" 1604 #define SECCOMP_RET_TRACE_NAME "trace" 1605 #define SECCOMP_RET_LOG_NAME "log" 1606 #define SECCOMP_RET_ALLOW_NAME "allow" 1607 1608 static const char seccomp_actions_avail[] = 1609 SECCOMP_RET_KILL_PROCESS_NAME " " 1610 SECCOMP_RET_KILL_THREAD_NAME " " 1611 SECCOMP_RET_TRAP_NAME " " 1612 SECCOMP_RET_ERRNO_NAME " " 1613 SECCOMP_RET_USER_NOTIF_NAME " " 1614 SECCOMP_RET_TRACE_NAME " " 1615 SECCOMP_RET_LOG_NAME " " 1616 SECCOMP_RET_ALLOW_NAME; 1617 1618 struct seccomp_log_name { 1619 u32 log; 1620 const char *name; 1621 }; 1622 1623 static const struct seccomp_log_name seccomp_log_names[] = { 1624 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, 1625 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, 1626 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, 1627 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, 1628 { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME }, 1629 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, 1630 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, 1631 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, 1632 { } 1633 }; 1634 1635 static bool seccomp_names_from_actions_logged(char *names, size_t size, 1636 u32 actions_logged, 1637 const char *sep) 1638 { 1639 const struct seccomp_log_name *cur; 1640 bool append_sep = false; 1641 1642 for (cur = seccomp_log_names; cur->name && size; cur++) { 1643 ssize_t ret; 1644 1645 if (!(actions_logged & cur->log)) 1646 continue; 1647 1648 if (append_sep) { 1649 ret = strscpy(names, sep, size); 1650 if (ret < 0) 1651 return false; 1652 1653 names += ret; 1654 size -= ret; 1655 } else 1656 append_sep = true; 1657 1658 ret = strscpy(names, cur->name, size); 1659 if (ret < 0) 1660 return false; 1661 1662 names += ret; 1663 size -= ret; 1664 } 1665 1666 return true; 1667 } 1668 1669 static bool seccomp_action_logged_from_name(u32 *action_logged, 1670 const char *name) 1671 { 1672 const struct seccomp_log_name *cur; 1673 1674 for (cur = seccomp_log_names; cur->name; cur++) { 1675 if (!strcmp(cur->name, name)) { 1676 *action_logged = cur->log; 1677 return true; 1678 } 1679 } 1680 1681 return false; 1682 } 1683 1684 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) 1685 { 1686 char *name; 1687 1688 *actions_logged = 0; 1689 while ((name = strsep(&names, " ")) && *name) { 1690 u32 action_logged = 0; 1691 1692 if (!seccomp_action_logged_from_name(&action_logged, name)) 1693 return false; 1694 1695 *actions_logged |= action_logged; 1696 } 1697 1698 return true; 1699 } 1700 1701 static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1702 size_t *lenp, loff_t *ppos) 1703 { 1704 char names[sizeof(seccomp_actions_avail)]; 1705 struct ctl_table table; 1706 1707 memset(names, 0, sizeof(names)); 1708 1709 if (!seccomp_names_from_actions_logged(names, sizeof(names), 1710 seccomp_actions_logged, " ")) 1711 return -EINVAL; 1712 1713 table = *ro_table; 1714 table.data = names; 1715 table.maxlen = sizeof(names); 1716 return proc_dostring(&table, 0, buffer, lenp, ppos); 1717 } 1718 1719 static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1720 size_t *lenp, loff_t *ppos, u32 *actions_logged) 1721 { 1722 char names[sizeof(seccomp_actions_avail)]; 1723 struct ctl_table table; 1724 int ret; 1725 1726 if (!capable(CAP_SYS_ADMIN)) 1727 return -EPERM; 1728 1729 memset(names, 0, sizeof(names)); 1730 1731 table = *ro_table; 1732 table.data = names; 1733 table.maxlen = sizeof(names); 1734 ret = proc_dostring(&table, 1, buffer, lenp, ppos); 1735 if (ret) 1736 return ret; 1737 1738 if (!seccomp_actions_logged_from_names(actions_logged, table.data)) 1739 return -EINVAL; 1740 1741 if (*actions_logged & SECCOMP_LOG_ALLOW) 1742 return -EINVAL; 1743 1744 seccomp_actions_logged = *actions_logged; 1745 return 0; 1746 } 1747 1748 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, 1749 int ret) 1750 { 1751 char names[sizeof(seccomp_actions_avail)]; 1752 char old_names[sizeof(seccomp_actions_avail)]; 1753 const char *new = names; 1754 const char *old = old_names; 1755 1756 if (!audit_enabled) 1757 return; 1758 1759 memset(names, 0, sizeof(names)); 1760 memset(old_names, 0, sizeof(old_names)); 1761 1762 if (ret) 1763 new = "?"; 1764 else if (!actions_logged) 1765 new = "(none)"; 1766 else if (!seccomp_names_from_actions_logged(names, sizeof(names), 1767 actions_logged, ",")) 1768 new = "?"; 1769 1770 if (!old_actions_logged) 1771 old = "(none)"; 1772 else if (!seccomp_names_from_actions_logged(old_names, 1773 sizeof(old_names), 1774 old_actions_logged, ",")) 1775 old = "?"; 1776 1777 return audit_seccomp_actions_logged(new, old, !ret); 1778 } 1779 1780 static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write, 1781 void __user *buffer, size_t *lenp, 1782 loff_t *ppos) 1783 { 1784 int ret; 1785 1786 if (write) { 1787 u32 actions_logged = 0; 1788 u32 old_actions_logged = seccomp_actions_logged; 1789 1790 ret = write_actions_logged(ro_table, buffer, lenp, ppos, 1791 &actions_logged); 1792 audit_actions_logged(actions_logged, old_actions_logged, ret); 1793 } else 1794 ret = read_actions_logged(ro_table, buffer, lenp, ppos); 1795 1796 return ret; 1797 } 1798 1799 static struct ctl_path seccomp_sysctl_path[] = { 1800 { .procname = "kernel", }, 1801 { .procname = "seccomp", }, 1802 { } 1803 }; 1804 1805 static struct ctl_table seccomp_sysctl_table[] = { 1806 { 1807 .procname = "actions_avail", 1808 .data = (void *) &seccomp_actions_avail, 1809 .maxlen = sizeof(seccomp_actions_avail), 1810 .mode = 0444, 1811 .proc_handler = proc_dostring, 1812 }, 1813 { 1814 .procname = "actions_logged", 1815 .mode = 0644, 1816 .proc_handler = seccomp_actions_logged_handler, 1817 }, 1818 { } 1819 }; 1820 1821 static int __init seccomp_sysctl_init(void) 1822 { 1823 struct ctl_table_header *hdr; 1824 1825 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table); 1826 if (!hdr) 1827 pr_warn("seccomp: sysctl registration failed\n"); 1828 else 1829 kmemleak_not_leak(hdr); 1830 1831 return 0; 1832 } 1833 1834 device_initcall(seccomp_sysctl_init) 1835 1836 #endif /* CONFIG_SYSCTL */ 1837