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 return ret; 533 } 534 535 /* Set log flag, if present. */ 536 if (flags & SECCOMP_FILTER_FLAG_LOG) 537 filter->log = true; 538 539 /* 540 * If there is an existing filter, make it the prev and don't drop its 541 * task reference. 542 */ 543 filter->prev = current->seccomp.filter; 544 current->seccomp.filter = filter; 545 546 /* Now that the new filter is in place, synchronize to all threads. */ 547 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 548 seccomp_sync_threads(flags); 549 550 return 0; 551 } 552 553 static void __get_seccomp_filter(struct seccomp_filter *filter) 554 { 555 refcount_inc(&filter->usage); 556 } 557 558 /* get_seccomp_filter - increments the reference count of the filter on @tsk */ 559 void get_seccomp_filter(struct task_struct *tsk) 560 { 561 struct seccomp_filter *orig = tsk->seccomp.filter; 562 if (!orig) 563 return; 564 __get_seccomp_filter(orig); 565 } 566 567 static inline void seccomp_filter_free(struct seccomp_filter *filter) 568 { 569 if (filter) { 570 bpf_prog_destroy(filter->prog); 571 kfree(filter); 572 } 573 } 574 575 static void __put_seccomp_filter(struct seccomp_filter *orig) 576 { 577 /* Clean up single-reference branches iteratively. */ 578 while (orig && refcount_dec_and_test(&orig->usage)) { 579 struct seccomp_filter *freeme = orig; 580 orig = orig->prev; 581 seccomp_filter_free(freeme); 582 } 583 } 584 585 /* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */ 586 void put_seccomp_filter(struct task_struct *tsk) 587 { 588 __put_seccomp_filter(tsk->seccomp.filter); 589 } 590 591 static void seccomp_init_siginfo(kernel_siginfo_t *info, int syscall, int reason) 592 { 593 clear_siginfo(info); 594 info->si_signo = SIGSYS; 595 info->si_code = SYS_SECCOMP; 596 info->si_call_addr = (void __user *)KSTK_EIP(current); 597 info->si_errno = reason; 598 info->si_arch = syscall_get_arch(current); 599 info->si_syscall = syscall; 600 } 601 602 /** 603 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation 604 * @syscall: syscall number to send to userland 605 * @reason: filter-supplied reason code to send to userland (via si_errno) 606 * 607 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. 608 */ 609 static void seccomp_send_sigsys(int syscall, int reason) 610 { 611 struct kernel_siginfo info; 612 seccomp_init_siginfo(&info, syscall, reason); 613 force_sig_info(&info); 614 } 615 #endif /* CONFIG_SECCOMP_FILTER */ 616 617 /* For use with seccomp_actions_logged */ 618 #define SECCOMP_LOG_KILL_PROCESS (1 << 0) 619 #define SECCOMP_LOG_KILL_THREAD (1 << 1) 620 #define SECCOMP_LOG_TRAP (1 << 2) 621 #define SECCOMP_LOG_ERRNO (1 << 3) 622 #define SECCOMP_LOG_TRACE (1 << 4) 623 #define SECCOMP_LOG_LOG (1 << 5) 624 #define SECCOMP_LOG_ALLOW (1 << 6) 625 #define SECCOMP_LOG_USER_NOTIF (1 << 7) 626 627 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | 628 SECCOMP_LOG_KILL_THREAD | 629 SECCOMP_LOG_TRAP | 630 SECCOMP_LOG_ERRNO | 631 SECCOMP_LOG_USER_NOTIF | 632 SECCOMP_LOG_TRACE | 633 SECCOMP_LOG_LOG; 634 635 static inline void seccomp_log(unsigned long syscall, long signr, u32 action, 636 bool requested) 637 { 638 bool log = false; 639 640 switch (action) { 641 case SECCOMP_RET_ALLOW: 642 break; 643 case SECCOMP_RET_TRAP: 644 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; 645 break; 646 case SECCOMP_RET_ERRNO: 647 log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; 648 break; 649 case SECCOMP_RET_TRACE: 650 log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; 651 break; 652 case SECCOMP_RET_USER_NOTIF: 653 log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF; 654 break; 655 case SECCOMP_RET_LOG: 656 log = seccomp_actions_logged & SECCOMP_LOG_LOG; 657 break; 658 case SECCOMP_RET_KILL_THREAD: 659 log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; 660 break; 661 case SECCOMP_RET_KILL_PROCESS: 662 default: 663 log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; 664 } 665 666 /* 667 * Emit an audit message when the action is RET_KILL_*, RET_LOG, or the 668 * FILTER_FLAG_LOG bit was set. The admin has the ability to silence 669 * any action from being logged by removing the action name from the 670 * seccomp_actions_logged sysctl. 671 */ 672 if (!log) 673 return; 674 675 audit_seccomp(syscall, signr, action); 676 } 677 678 /* 679 * Secure computing mode 1 allows only read/write/exit/sigreturn. 680 * To be fully secure this must be combined with rlimit 681 * to limit the stack allocations too. 682 */ 683 static const int mode1_syscalls[] = { 684 __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn, 685 0, /* null terminated */ 686 }; 687 688 static void __secure_computing_strict(int this_syscall) 689 { 690 const int *syscall_whitelist = mode1_syscalls; 691 #ifdef CONFIG_COMPAT 692 if (in_compat_syscall()) 693 syscall_whitelist = get_compat_mode1_syscalls(); 694 #endif 695 do { 696 if (*syscall_whitelist == this_syscall) 697 return; 698 } while (*++syscall_whitelist); 699 700 #ifdef SECCOMP_DEBUG 701 dump_stack(); 702 #endif 703 seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); 704 do_exit(SIGKILL); 705 } 706 707 #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER 708 void secure_computing_strict(int this_syscall) 709 { 710 int mode = current->seccomp.mode; 711 712 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 713 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 714 return; 715 716 if (mode == SECCOMP_MODE_DISABLED) 717 return; 718 else if (mode == SECCOMP_MODE_STRICT) 719 __secure_computing_strict(this_syscall); 720 else 721 BUG(); 722 } 723 #else 724 725 #ifdef CONFIG_SECCOMP_FILTER 726 static u64 seccomp_next_notify_id(struct seccomp_filter *filter) 727 { 728 /* 729 * Note: overflow is ok here, the id just needs to be unique per 730 * filter. 731 */ 732 lockdep_assert_held(&filter->notify_lock); 733 return filter->notif->next_id++; 734 } 735 736 static int seccomp_do_user_notification(int this_syscall, 737 struct seccomp_filter *match, 738 const struct seccomp_data *sd) 739 { 740 int err; 741 u32 flags = 0; 742 long ret = 0; 743 struct seccomp_knotif n = {}; 744 745 mutex_lock(&match->notify_lock); 746 err = -ENOSYS; 747 if (!match->notif) 748 goto out; 749 750 n.task = current; 751 n.state = SECCOMP_NOTIFY_INIT; 752 n.data = sd; 753 n.id = seccomp_next_notify_id(match); 754 init_completion(&n.ready); 755 list_add(&n.list, &match->notif->notifications); 756 757 up(&match->notif->request); 758 wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM); 759 mutex_unlock(&match->notify_lock); 760 761 /* 762 * This is where we wait for a reply from userspace. 763 */ 764 err = wait_for_completion_interruptible(&n.ready); 765 mutex_lock(&match->notify_lock); 766 if (err == 0) { 767 ret = n.val; 768 err = n.error; 769 flags = n.flags; 770 } 771 772 /* 773 * Note that it's possible the listener died in between the time when 774 * we were notified of a respons (or a signal) and when we were able to 775 * re-acquire the lock, so only delete from the list if the 776 * notification actually exists. 777 * 778 * Also note that this test is only valid because there's no way to 779 * *reattach* to a notifier right now. If one is added, we'll need to 780 * keep track of the notif itself and make sure they match here. 781 */ 782 if (match->notif) 783 list_del(&n.list); 784 out: 785 mutex_unlock(&match->notify_lock); 786 787 /* Userspace requests to continue the syscall. */ 788 if (flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) 789 return 0; 790 791 syscall_set_return_value(current, task_pt_regs(current), 792 err, ret); 793 return -1; 794 } 795 796 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 797 const bool recheck_after_trace) 798 { 799 u32 filter_ret, action; 800 struct seccomp_filter *match = NULL; 801 int data; 802 struct seccomp_data sd_local; 803 804 /* 805 * Make sure that any changes to mode from another thread have 806 * been seen after TIF_SECCOMP was seen. 807 */ 808 rmb(); 809 810 if (!sd) { 811 populate_seccomp_data(&sd_local); 812 sd = &sd_local; 813 } 814 815 filter_ret = seccomp_run_filters(sd, &match); 816 data = filter_ret & SECCOMP_RET_DATA; 817 action = filter_ret & SECCOMP_RET_ACTION_FULL; 818 819 switch (action) { 820 case SECCOMP_RET_ERRNO: 821 /* Set low-order bits as an errno, capped at MAX_ERRNO. */ 822 if (data > MAX_ERRNO) 823 data = MAX_ERRNO; 824 syscall_set_return_value(current, task_pt_regs(current), 825 -data, 0); 826 goto skip; 827 828 case SECCOMP_RET_TRAP: 829 /* Show the handler the original registers. */ 830 syscall_rollback(current, task_pt_regs(current)); 831 /* Let the filter pass back 16 bits of data. */ 832 seccomp_send_sigsys(this_syscall, data); 833 goto skip; 834 835 case SECCOMP_RET_TRACE: 836 /* We've been put in this state by the ptracer already. */ 837 if (recheck_after_trace) 838 return 0; 839 840 /* ENOSYS these calls if there is no tracer attached. */ 841 if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) { 842 syscall_set_return_value(current, 843 task_pt_regs(current), 844 -ENOSYS, 0); 845 goto skip; 846 } 847 848 /* Allow the BPF to provide the event message */ 849 ptrace_event(PTRACE_EVENT_SECCOMP, data); 850 /* 851 * The delivery of a fatal signal during event 852 * notification may silently skip tracer notification, 853 * which could leave us with a potentially unmodified 854 * syscall that the tracer would have liked to have 855 * changed. Since the process is about to die, we just 856 * force the syscall to be skipped and let the signal 857 * kill the process and correctly handle any tracer exit 858 * notifications. 859 */ 860 if (fatal_signal_pending(current)) 861 goto skip; 862 /* Check if the tracer forced the syscall to be skipped. */ 863 this_syscall = syscall_get_nr(current, task_pt_regs(current)); 864 if (this_syscall < 0) 865 goto skip; 866 867 /* 868 * Recheck the syscall, since it may have changed. This 869 * intentionally uses a NULL struct seccomp_data to force 870 * a reload of all registers. This does not goto skip since 871 * a skip would have already been reported. 872 */ 873 if (__seccomp_filter(this_syscall, NULL, true)) 874 return -1; 875 876 return 0; 877 878 case SECCOMP_RET_USER_NOTIF: 879 if (seccomp_do_user_notification(this_syscall, match, sd)) 880 goto skip; 881 882 return 0; 883 884 case SECCOMP_RET_LOG: 885 seccomp_log(this_syscall, 0, action, true); 886 return 0; 887 888 case SECCOMP_RET_ALLOW: 889 /* 890 * Note that the "match" filter will always be NULL for 891 * this action since SECCOMP_RET_ALLOW is the starting 892 * state in seccomp_run_filters(). 893 */ 894 return 0; 895 896 case SECCOMP_RET_KILL_THREAD: 897 case SECCOMP_RET_KILL_PROCESS: 898 default: 899 seccomp_log(this_syscall, SIGSYS, action, true); 900 /* Dump core only if this is the last remaining thread. */ 901 if (action == SECCOMP_RET_KILL_PROCESS || 902 get_nr_threads(current) == 1) { 903 kernel_siginfo_t info; 904 905 /* Show the original registers in the dump. */ 906 syscall_rollback(current, task_pt_regs(current)); 907 /* Trigger a manual coredump since do_exit skips it. */ 908 seccomp_init_siginfo(&info, this_syscall, data); 909 do_coredump(&info); 910 } 911 if (action == SECCOMP_RET_KILL_PROCESS) 912 do_group_exit(SIGSYS); 913 else 914 do_exit(SIGSYS); 915 } 916 917 unreachable(); 918 919 skip: 920 seccomp_log(this_syscall, 0, action, match ? match->log : false); 921 return -1; 922 } 923 #else 924 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, 925 const bool recheck_after_trace) 926 { 927 BUG(); 928 } 929 #endif 930 931 int __secure_computing(const struct seccomp_data *sd) 932 { 933 int mode = current->seccomp.mode; 934 int this_syscall; 935 936 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && 937 unlikely(current->ptrace & PT_SUSPEND_SECCOMP)) 938 return 0; 939 940 this_syscall = sd ? sd->nr : 941 syscall_get_nr(current, task_pt_regs(current)); 942 943 switch (mode) { 944 case SECCOMP_MODE_STRICT: 945 __secure_computing_strict(this_syscall); /* may call do_exit */ 946 return 0; 947 case SECCOMP_MODE_FILTER: 948 return __seccomp_filter(this_syscall, sd, false); 949 default: 950 BUG(); 951 } 952 } 953 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */ 954 955 long prctl_get_seccomp(void) 956 { 957 return current->seccomp.mode; 958 } 959 960 /** 961 * seccomp_set_mode_strict: internal function for setting strict seccomp 962 * 963 * Once current->seccomp.mode is non-zero, it may not be changed. 964 * 965 * Returns 0 on success or -EINVAL on failure. 966 */ 967 static long seccomp_set_mode_strict(void) 968 { 969 const unsigned long seccomp_mode = SECCOMP_MODE_STRICT; 970 long ret = -EINVAL; 971 972 spin_lock_irq(¤t->sighand->siglock); 973 974 if (!seccomp_may_assign_mode(seccomp_mode)) 975 goto out; 976 977 #ifdef TIF_NOTSC 978 disable_TSC(); 979 #endif 980 seccomp_assign_mode(current, seccomp_mode, 0); 981 ret = 0; 982 983 out: 984 spin_unlock_irq(¤t->sighand->siglock); 985 986 return ret; 987 } 988 989 #ifdef CONFIG_SECCOMP_FILTER 990 static int seccomp_notify_release(struct inode *inode, struct file *file) 991 { 992 struct seccomp_filter *filter = file->private_data; 993 struct seccomp_knotif *knotif; 994 995 if (!filter) 996 return 0; 997 998 mutex_lock(&filter->notify_lock); 999 1000 /* 1001 * If this file is being closed because e.g. the task who owned it 1002 * died, let's wake everyone up who was waiting on us. 1003 */ 1004 list_for_each_entry(knotif, &filter->notif->notifications, list) { 1005 if (knotif->state == SECCOMP_NOTIFY_REPLIED) 1006 continue; 1007 1008 knotif->state = SECCOMP_NOTIFY_REPLIED; 1009 knotif->error = -ENOSYS; 1010 knotif->val = 0; 1011 1012 complete(&knotif->ready); 1013 } 1014 1015 kfree(filter->notif); 1016 filter->notif = NULL; 1017 mutex_unlock(&filter->notify_lock); 1018 __put_seccomp_filter(filter); 1019 return 0; 1020 } 1021 1022 static long seccomp_notify_recv(struct seccomp_filter *filter, 1023 void __user *buf) 1024 { 1025 struct seccomp_knotif *knotif = NULL, *cur; 1026 struct seccomp_notif unotif; 1027 ssize_t ret; 1028 1029 /* Verify that we're not given garbage to keep struct extensible. */ 1030 ret = check_zeroed_user(buf, sizeof(unotif)); 1031 if (ret < 0) 1032 return ret; 1033 if (!ret) 1034 return -EINVAL; 1035 1036 memset(&unotif, 0, sizeof(unotif)); 1037 1038 ret = down_interruptible(&filter->notif->request); 1039 if (ret < 0) 1040 return ret; 1041 1042 mutex_lock(&filter->notify_lock); 1043 list_for_each_entry(cur, &filter->notif->notifications, list) { 1044 if (cur->state == SECCOMP_NOTIFY_INIT) { 1045 knotif = cur; 1046 break; 1047 } 1048 } 1049 1050 /* 1051 * If we didn't find a notification, it could be that the task was 1052 * interrupted by a fatal signal between the time we were woken and 1053 * when we were able to acquire the rw lock. 1054 */ 1055 if (!knotif) { 1056 ret = -ENOENT; 1057 goto out; 1058 } 1059 1060 unotif.id = knotif->id; 1061 unotif.pid = task_pid_vnr(knotif->task); 1062 unotif.data = *(knotif->data); 1063 1064 knotif->state = SECCOMP_NOTIFY_SENT; 1065 wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM); 1066 ret = 0; 1067 out: 1068 mutex_unlock(&filter->notify_lock); 1069 1070 if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) { 1071 ret = -EFAULT; 1072 1073 /* 1074 * Userspace screwed up. To make sure that we keep this 1075 * notification alive, let's reset it back to INIT. It 1076 * may have died when we released the lock, so we need to make 1077 * sure it's still around. 1078 */ 1079 knotif = NULL; 1080 mutex_lock(&filter->notify_lock); 1081 list_for_each_entry(cur, &filter->notif->notifications, list) { 1082 if (cur->id == unotif.id) { 1083 knotif = cur; 1084 break; 1085 } 1086 } 1087 1088 if (knotif) { 1089 knotif->state = SECCOMP_NOTIFY_INIT; 1090 up(&filter->notif->request); 1091 } 1092 mutex_unlock(&filter->notify_lock); 1093 } 1094 1095 return ret; 1096 } 1097 1098 static long seccomp_notify_send(struct seccomp_filter *filter, 1099 void __user *buf) 1100 { 1101 struct seccomp_notif_resp resp = {}; 1102 struct seccomp_knotif *knotif = NULL, *cur; 1103 long ret; 1104 1105 if (copy_from_user(&resp, buf, sizeof(resp))) 1106 return -EFAULT; 1107 1108 if (resp.flags & ~SECCOMP_USER_NOTIF_FLAG_CONTINUE) 1109 return -EINVAL; 1110 1111 if ((resp.flags & SECCOMP_USER_NOTIF_FLAG_CONTINUE) && 1112 (resp.error || resp.val)) 1113 return -EINVAL; 1114 1115 ret = mutex_lock_interruptible(&filter->notify_lock); 1116 if (ret < 0) 1117 return ret; 1118 1119 list_for_each_entry(cur, &filter->notif->notifications, list) { 1120 if (cur->id == resp.id) { 1121 knotif = cur; 1122 break; 1123 } 1124 } 1125 1126 if (!knotif) { 1127 ret = -ENOENT; 1128 goto out; 1129 } 1130 1131 /* Allow exactly one reply. */ 1132 if (knotif->state != SECCOMP_NOTIFY_SENT) { 1133 ret = -EINPROGRESS; 1134 goto out; 1135 } 1136 1137 ret = 0; 1138 knotif->state = SECCOMP_NOTIFY_REPLIED; 1139 knotif->error = resp.error; 1140 knotif->val = resp.val; 1141 knotif->flags = resp.flags; 1142 complete(&knotif->ready); 1143 out: 1144 mutex_unlock(&filter->notify_lock); 1145 return ret; 1146 } 1147 1148 static long seccomp_notify_id_valid(struct seccomp_filter *filter, 1149 void __user *buf) 1150 { 1151 struct seccomp_knotif *knotif = NULL; 1152 u64 id; 1153 long ret; 1154 1155 if (copy_from_user(&id, buf, sizeof(id))) 1156 return -EFAULT; 1157 1158 ret = mutex_lock_interruptible(&filter->notify_lock); 1159 if (ret < 0) 1160 return ret; 1161 1162 ret = -ENOENT; 1163 list_for_each_entry(knotif, &filter->notif->notifications, list) { 1164 if (knotif->id == id) { 1165 if (knotif->state == SECCOMP_NOTIFY_SENT) 1166 ret = 0; 1167 goto out; 1168 } 1169 } 1170 1171 out: 1172 mutex_unlock(&filter->notify_lock); 1173 return ret; 1174 } 1175 1176 static long seccomp_notify_ioctl(struct file *file, unsigned int cmd, 1177 unsigned long arg) 1178 { 1179 struct seccomp_filter *filter = file->private_data; 1180 void __user *buf = (void __user *)arg; 1181 1182 switch (cmd) { 1183 case SECCOMP_IOCTL_NOTIF_RECV: 1184 return seccomp_notify_recv(filter, buf); 1185 case SECCOMP_IOCTL_NOTIF_SEND: 1186 return seccomp_notify_send(filter, buf); 1187 case SECCOMP_IOCTL_NOTIF_ID_VALID: 1188 return seccomp_notify_id_valid(filter, buf); 1189 default: 1190 return -EINVAL; 1191 } 1192 } 1193 1194 static __poll_t seccomp_notify_poll(struct file *file, 1195 struct poll_table_struct *poll_tab) 1196 { 1197 struct seccomp_filter *filter = file->private_data; 1198 __poll_t ret = 0; 1199 struct seccomp_knotif *cur; 1200 1201 poll_wait(file, &filter->notif->wqh, poll_tab); 1202 1203 if (mutex_lock_interruptible(&filter->notify_lock) < 0) 1204 return EPOLLERR; 1205 1206 list_for_each_entry(cur, &filter->notif->notifications, list) { 1207 if (cur->state == SECCOMP_NOTIFY_INIT) 1208 ret |= EPOLLIN | EPOLLRDNORM; 1209 if (cur->state == SECCOMP_NOTIFY_SENT) 1210 ret |= EPOLLOUT | EPOLLWRNORM; 1211 if ((ret & EPOLLIN) && (ret & EPOLLOUT)) 1212 break; 1213 } 1214 1215 mutex_unlock(&filter->notify_lock); 1216 1217 return ret; 1218 } 1219 1220 static const struct file_operations seccomp_notify_ops = { 1221 .poll = seccomp_notify_poll, 1222 .release = seccomp_notify_release, 1223 .unlocked_ioctl = seccomp_notify_ioctl, 1224 }; 1225 1226 static struct file *init_listener(struct seccomp_filter *filter) 1227 { 1228 struct file *ret = ERR_PTR(-EBUSY); 1229 struct seccomp_filter *cur; 1230 1231 for (cur = current->seccomp.filter; cur; cur = cur->prev) { 1232 if (cur->notif) 1233 goto out; 1234 } 1235 1236 ret = ERR_PTR(-ENOMEM); 1237 filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL); 1238 if (!filter->notif) 1239 goto out; 1240 1241 sema_init(&filter->notif->request, 0); 1242 filter->notif->next_id = get_random_u64(); 1243 INIT_LIST_HEAD(&filter->notif->notifications); 1244 init_waitqueue_head(&filter->notif->wqh); 1245 1246 ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops, 1247 filter, O_RDWR); 1248 if (IS_ERR(ret)) 1249 goto out_notif; 1250 1251 /* The file has a reference to it now */ 1252 __get_seccomp_filter(filter); 1253 1254 out_notif: 1255 if (IS_ERR(ret)) 1256 kfree(filter->notif); 1257 out: 1258 return ret; 1259 } 1260 1261 /** 1262 * seccomp_set_mode_filter: internal function for setting seccomp filter 1263 * @flags: flags to change filter behavior 1264 * @filter: struct sock_fprog containing filter 1265 * 1266 * This function may be called repeatedly to install additional filters. 1267 * Every filter successfully installed will be evaluated (in reverse order) 1268 * for each system call the task makes. 1269 * 1270 * Once current->seccomp.mode is non-zero, it may not be changed. 1271 * 1272 * Returns 0 on success or -EINVAL on failure. 1273 */ 1274 static long seccomp_set_mode_filter(unsigned int flags, 1275 const char __user *filter) 1276 { 1277 const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; 1278 struct seccomp_filter *prepared = NULL; 1279 long ret = -EINVAL; 1280 int listener = -1; 1281 struct file *listener_f = NULL; 1282 1283 /* Validate flags. */ 1284 if (flags & ~SECCOMP_FILTER_FLAG_MASK) 1285 return -EINVAL; 1286 1287 /* 1288 * In the successful case, NEW_LISTENER returns the new listener fd. 1289 * But in the failure case, TSYNC returns the thread that died. If you 1290 * combine these two flags, there's no way to tell whether something 1291 * succeeded or failed. So, let's disallow this combination. 1292 */ 1293 if ((flags & SECCOMP_FILTER_FLAG_TSYNC) && 1294 (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER)) 1295 return -EINVAL; 1296 1297 /* Prepare the new filter before holding any locks. */ 1298 prepared = seccomp_prepare_user_filter(filter); 1299 if (IS_ERR(prepared)) 1300 return PTR_ERR(prepared); 1301 1302 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 1303 listener = get_unused_fd_flags(O_CLOEXEC); 1304 if (listener < 0) { 1305 ret = listener; 1306 goto out_free; 1307 } 1308 1309 listener_f = init_listener(prepared); 1310 if (IS_ERR(listener_f)) { 1311 put_unused_fd(listener); 1312 ret = PTR_ERR(listener_f); 1313 goto out_free; 1314 } 1315 } 1316 1317 /* 1318 * Make sure we cannot change seccomp or nnp state via TSYNC 1319 * while another thread is in the middle of calling exec. 1320 */ 1321 if (flags & SECCOMP_FILTER_FLAG_TSYNC && 1322 mutex_lock_killable(¤t->signal->cred_guard_mutex)) 1323 goto out_put_fd; 1324 1325 spin_lock_irq(¤t->sighand->siglock); 1326 1327 if (!seccomp_may_assign_mode(seccomp_mode)) 1328 goto out; 1329 1330 ret = seccomp_attach_filter(flags, prepared); 1331 if (ret) 1332 goto out; 1333 /* Do not free the successfully attached filter. */ 1334 prepared = NULL; 1335 1336 seccomp_assign_mode(current, seccomp_mode, flags); 1337 out: 1338 spin_unlock_irq(¤t->sighand->siglock); 1339 if (flags & SECCOMP_FILTER_FLAG_TSYNC) 1340 mutex_unlock(¤t->signal->cred_guard_mutex); 1341 out_put_fd: 1342 if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) { 1343 if (ret) { 1344 listener_f->private_data = NULL; 1345 fput(listener_f); 1346 put_unused_fd(listener); 1347 } else { 1348 fd_install(listener, listener_f); 1349 ret = listener; 1350 } 1351 } 1352 out_free: 1353 seccomp_filter_free(prepared); 1354 return ret; 1355 } 1356 #else 1357 static inline long seccomp_set_mode_filter(unsigned int flags, 1358 const char __user *filter) 1359 { 1360 return -EINVAL; 1361 } 1362 #endif 1363 1364 static long seccomp_get_action_avail(const char __user *uaction) 1365 { 1366 u32 action; 1367 1368 if (copy_from_user(&action, uaction, sizeof(action))) 1369 return -EFAULT; 1370 1371 switch (action) { 1372 case SECCOMP_RET_KILL_PROCESS: 1373 case SECCOMP_RET_KILL_THREAD: 1374 case SECCOMP_RET_TRAP: 1375 case SECCOMP_RET_ERRNO: 1376 case SECCOMP_RET_USER_NOTIF: 1377 case SECCOMP_RET_TRACE: 1378 case SECCOMP_RET_LOG: 1379 case SECCOMP_RET_ALLOW: 1380 break; 1381 default: 1382 return -EOPNOTSUPP; 1383 } 1384 1385 return 0; 1386 } 1387 1388 static long seccomp_get_notif_sizes(void __user *usizes) 1389 { 1390 struct seccomp_notif_sizes sizes = { 1391 .seccomp_notif = sizeof(struct seccomp_notif), 1392 .seccomp_notif_resp = sizeof(struct seccomp_notif_resp), 1393 .seccomp_data = sizeof(struct seccomp_data), 1394 }; 1395 1396 if (copy_to_user(usizes, &sizes, sizeof(sizes))) 1397 return -EFAULT; 1398 1399 return 0; 1400 } 1401 1402 /* Common entry point for both prctl and syscall. */ 1403 static long do_seccomp(unsigned int op, unsigned int flags, 1404 void __user *uargs) 1405 { 1406 switch (op) { 1407 case SECCOMP_SET_MODE_STRICT: 1408 if (flags != 0 || uargs != NULL) 1409 return -EINVAL; 1410 return seccomp_set_mode_strict(); 1411 case SECCOMP_SET_MODE_FILTER: 1412 return seccomp_set_mode_filter(flags, uargs); 1413 case SECCOMP_GET_ACTION_AVAIL: 1414 if (flags != 0) 1415 return -EINVAL; 1416 1417 return seccomp_get_action_avail(uargs); 1418 case SECCOMP_GET_NOTIF_SIZES: 1419 if (flags != 0) 1420 return -EINVAL; 1421 1422 return seccomp_get_notif_sizes(uargs); 1423 default: 1424 return -EINVAL; 1425 } 1426 } 1427 1428 SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags, 1429 void __user *, uargs) 1430 { 1431 return do_seccomp(op, flags, uargs); 1432 } 1433 1434 /** 1435 * prctl_set_seccomp: configures current->seccomp.mode 1436 * @seccomp_mode: requested mode to use 1437 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER 1438 * 1439 * Returns 0 on success or -EINVAL on failure. 1440 */ 1441 long prctl_set_seccomp(unsigned long seccomp_mode, void __user *filter) 1442 { 1443 unsigned int op; 1444 void __user *uargs; 1445 1446 switch (seccomp_mode) { 1447 case SECCOMP_MODE_STRICT: 1448 op = SECCOMP_SET_MODE_STRICT; 1449 /* 1450 * Setting strict mode through prctl always ignored filter, 1451 * so make sure it is always NULL here to pass the internal 1452 * check in do_seccomp(). 1453 */ 1454 uargs = NULL; 1455 break; 1456 case SECCOMP_MODE_FILTER: 1457 op = SECCOMP_SET_MODE_FILTER; 1458 uargs = filter; 1459 break; 1460 default: 1461 return -EINVAL; 1462 } 1463 1464 /* prctl interface doesn't have flags, so they are always zero. */ 1465 return do_seccomp(op, 0, uargs); 1466 } 1467 1468 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE) 1469 static struct seccomp_filter *get_nth_filter(struct task_struct *task, 1470 unsigned long filter_off) 1471 { 1472 struct seccomp_filter *orig, *filter; 1473 unsigned long count; 1474 1475 /* 1476 * Note: this is only correct because the caller should be the (ptrace) 1477 * tracer of the task, otherwise lock_task_sighand is needed. 1478 */ 1479 spin_lock_irq(&task->sighand->siglock); 1480 1481 if (task->seccomp.mode != SECCOMP_MODE_FILTER) { 1482 spin_unlock_irq(&task->sighand->siglock); 1483 return ERR_PTR(-EINVAL); 1484 } 1485 1486 orig = task->seccomp.filter; 1487 __get_seccomp_filter(orig); 1488 spin_unlock_irq(&task->sighand->siglock); 1489 1490 count = 0; 1491 for (filter = orig; filter; filter = filter->prev) 1492 count++; 1493 1494 if (filter_off >= count) { 1495 filter = ERR_PTR(-ENOENT); 1496 goto out; 1497 } 1498 1499 count -= filter_off; 1500 for (filter = orig; filter && count > 1; filter = filter->prev) 1501 count--; 1502 1503 if (WARN_ON(count != 1 || !filter)) { 1504 filter = ERR_PTR(-ENOENT); 1505 goto out; 1506 } 1507 1508 __get_seccomp_filter(filter); 1509 1510 out: 1511 __put_seccomp_filter(orig); 1512 return filter; 1513 } 1514 1515 long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, 1516 void __user *data) 1517 { 1518 struct seccomp_filter *filter; 1519 struct sock_fprog_kern *fprog; 1520 long ret; 1521 1522 if (!capable(CAP_SYS_ADMIN) || 1523 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1524 return -EACCES; 1525 } 1526 1527 filter = get_nth_filter(task, filter_off); 1528 if (IS_ERR(filter)) 1529 return PTR_ERR(filter); 1530 1531 fprog = filter->prog->orig_prog; 1532 if (!fprog) { 1533 /* This must be a new non-cBPF filter, since we save 1534 * every cBPF filter's orig_prog above when 1535 * CONFIG_CHECKPOINT_RESTORE is enabled. 1536 */ 1537 ret = -EMEDIUMTYPE; 1538 goto out; 1539 } 1540 1541 ret = fprog->len; 1542 if (!data) 1543 goto out; 1544 1545 if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) 1546 ret = -EFAULT; 1547 1548 out: 1549 __put_seccomp_filter(filter); 1550 return ret; 1551 } 1552 1553 long seccomp_get_metadata(struct task_struct *task, 1554 unsigned long size, void __user *data) 1555 { 1556 long ret; 1557 struct seccomp_filter *filter; 1558 struct seccomp_metadata kmd = {}; 1559 1560 if (!capable(CAP_SYS_ADMIN) || 1561 current->seccomp.mode != SECCOMP_MODE_DISABLED) { 1562 return -EACCES; 1563 } 1564 1565 size = min_t(unsigned long, size, sizeof(kmd)); 1566 1567 if (size < sizeof(kmd.filter_off)) 1568 return -EINVAL; 1569 1570 if (copy_from_user(&kmd.filter_off, data, sizeof(kmd.filter_off))) 1571 return -EFAULT; 1572 1573 filter = get_nth_filter(task, kmd.filter_off); 1574 if (IS_ERR(filter)) 1575 return PTR_ERR(filter); 1576 1577 if (filter->log) 1578 kmd.flags |= SECCOMP_FILTER_FLAG_LOG; 1579 1580 ret = size; 1581 if (copy_to_user(data, &kmd, size)) 1582 ret = -EFAULT; 1583 1584 __put_seccomp_filter(filter); 1585 return ret; 1586 } 1587 #endif 1588 1589 #ifdef CONFIG_SYSCTL 1590 1591 /* Human readable action names for friendly sysctl interaction */ 1592 #define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" 1593 #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" 1594 #define SECCOMP_RET_TRAP_NAME "trap" 1595 #define SECCOMP_RET_ERRNO_NAME "errno" 1596 #define SECCOMP_RET_USER_NOTIF_NAME "user_notif" 1597 #define SECCOMP_RET_TRACE_NAME "trace" 1598 #define SECCOMP_RET_LOG_NAME "log" 1599 #define SECCOMP_RET_ALLOW_NAME "allow" 1600 1601 static const char seccomp_actions_avail[] = 1602 SECCOMP_RET_KILL_PROCESS_NAME " " 1603 SECCOMP_RET_KILL_THREAD_NAME " " 1604 SECCOMP_RET_TRAP_NAME " " 1605 SECCOMP_RET_ERRNO_NAME " " 1606 SECCOMP_RET_USER_NOTIF_NAME " " 1607 SECCOMP_RET_TRACE_NAME " " 1608 SECCOMP_RET_LOG_NAME " " 1609 SECCOMP_RET_ALLOW_NAME; 1610 1611 struct seccomp_log_name { 1612 u32 log; 1613 const char *name; 1614 }; 1615 1616 static const struct seccomp_log_name seccomp_log_names[] = { 1617 { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, 1618 { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, 1619 { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, 1620 { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, 1621 { SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME }, 1622 { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, 1623 { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, 1624 { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, 1625 { } 1626 }; 1627 1628 static bool seccomp_names_from_actions_logged(char *names, size_t size, 1629 u32 actions_logged, 1630 const char *sep) 1631 { 1632 const struct seccomp_log_name *cur; 1633 bool append_sep = false; 1634 1635 for (cur = seccomp_log_names; cur->name && size; cur++) { 1636 ssize_t ret; 1637 1638 if (!(actions_logged & cur->log)) 1639 continue; 1640 1641 if (append_sep) { 1642 ret = strscpy(names, sep, size); 1643 if (ret < 0) 1644 return false; 1645 1646 names += ret; 1647 size -= ret; 1648 } else 1649 append_sep = true; 1650 1651 ret = strscpy(names, cur->name, size); 1652 if (ret < 0) 1653 return false; 1654 1655 names += ret; 1656 size -= ret; 1657 } 1658 1659 return true; 1660 } 1661 1662 static bool seccomp_action_logged_from_name(u32 *action_logged, 1663 const char *name) 1664 { 1665 const struct seccomp_log_name *cur; 1666 1667 for (cur = seccomp_log_names; cur->name; cur++) { 1668 if (!strcmp(cur->name, name)) { 1669 *action_logged = cur->log; 1670 return true; 1671 } 1672 } 1673 1674 return false; 1675 } 1676 1677 static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) 1678 { 1679 char *name; 1680 1681 *actions_logged = 0; 1682 while ((name = strsep(&names, " ")) && *name) { 1683 u32 action_logged = 0; 1684 1685 if (!seccomp_action_logged_from_name(&action_logged, name)) 1686 return false; 1687 1688 *actions_logged |= action_logged; 1689 } 1690 1691 return true; 1692 } 1693 1694 static int read_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1695 size_t *lenp, loff_t *ppos) 1696 { 1697 char names[sizeof(seccomp_actions_avail)]; 1698 struct ctl_table table; 1699 1700 memset(names, 0, sizeof(names)); 1701 1702 if (!seccomp_names_from_actions_logged(names, sizeof(names), 1703 seccomp_actions_logged, " ")) 1704 return -EINVAL; 1705 1706 table = *ro_table; 1707 table.data = names; 1708 table.maxlen = sizeof(names); 1709 return proc_dostring(&table, 0, buffer, lenp, ppos); 1710 } 1711 1712 static int write_actions_logged(struct ctl_table *ro_table, void __user *buffer, 1713 size_t *lenp, loff_t *ppos, u32 *actions_logged) 1714 { 1715 char names[sizeof(seccomp_actions_avail)]; 1716 struct ctl_table table; 1717 int ret; 1718 1719 if (!capable(CAP_SYS_ADMIN)) 1720 return -EPERM; 1721 1722 memset(names, 0, sizeof(names)); 1723 1724 table = *ro_table; 1725 table.data = names; 1726 table.maxlen = sizeof(names); 1727 ret = proc_dostring(&table, 1, buffer, lenp, ppos); 1728 if (ret) 1729 return ret; 1730 1731 if (!seccomp_actions_logged_from_names(actions_logged, table.data)) 1732 return -EINVAL; 1733 1734 if (*actions_logged & SECCOMP_LOG_ALLOW) 1735 return -EINVAL; 1736 1737 seccomp_actions_logged = *actions_logged; 1738 return 0; 1739 } 1740 1741 static void audit_actions_logged(u32 actions_logged, u32 old_actions_logged, 1742 int ret) 1743 { 1744 char names[sizeof(seccomp_actions_avail)]; 1745 char old_names[sizeof(seccomp_actions_avail)]; 1746 const char *new = names; 1747 const char *old = old_names; 1748 1749 if (!audit_enabled) 1750 return; 1751 1752 memset(names, 0, sizeof(names)); 1753 memset(old_names, 0, sizeof(old_names)); 1754 1755 if (ret) 1756 new = "?"; 1757 else if (!actions_logged) 1758 new = "(none)"; 1759 else if (!seccomp_names_from_actions_logged(names, sizeof(names), 1760 actions_logged, ",")) 1761 new = "?"; 1762 1763 if (!old_actions_logged) 1764 old = "(none)"; 1765 else if (!seccomp_names_from_actions_logged(old_names, 1766 sizeof(old_names), 1767 old_actions_logged, ",")) 1768 old = "?"; 1769 1770 return audit_seccomp_actions_logged(new, old, !ret); 1771 } 1772 1773 static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write, 1774 void __user *buffer, size_t *lenp, 1775 loff_t *ppos) 1776 { 1777 int ret; 1778 1779 if (write) { 1780 u32 actions_logged = 0; 1781 u32 old_actions_logged = seccomp_actions_logged; 1782 1783 ret = write_actions_logged(ro_table, buffer, lenp, ppos, 1784 &actions_logged); 1785 audit_actions_logged(actions_logged, old_actions_logged, ret); 1786 } else 1787 ret = read_actions_logged(ro_table, buffer, lenp, ppos); 1788 1789 return ret; 1790 } 1791 1792 static struct ctl_path seccomp_sysctl_path[] = { 1793 { .procname = "kernel", }, 1794 { .procname = "seccomp", }, 1795 { } 1796 }; 1797 1798 static struct ctl_table seccomp_sysctl_table[] = { 1799 { 1800 .procname = "actions_avail", 1801 .data = (void *) &seccomp_actions_avail, 1802 .maxlen = sizeof(seccomp_actions_avail), 1803 .mode = 0444, 1804 .proc_handler = proc_dostring, 1805 }, 1806 { 1807 .procname = "actions_logged", 1808 .mode = 0644, 1809 .proc_handler = seccomp_actions_logged_handler, 1810 }, 1811 { } 1812 }; 1813 1814 static int __init seccomp_sysctl_init(void) 1815 { 1816 struct ctl_table_header *hdr; 1817 1818 hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table); 1819 if (!hdr) 1820 pr_warn("seccomp: sysctl registration failed\n"); 1821 else 1822 kmemleak_not_leak(hdr); 1823 1824 return 0; 1825 } 1826 1827 device_initcall(seccomp_sysctl_init) 1828 1829 #endif /* CONFIG_SYSCTL */ 1830