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