| 1 | |
| 2 | * linux/kernel/seccomp.c
|
| 3 | *
|
| 4 | * Copyright 2004-2005 Andrea Arcangeli <[email protected]>
|
| 5 | *
|
| 6 | * Copyright (C) 2012 Google, Inc.
|
| 7 | * Will Drewry <[email protected]>
|
| 8 | *
|
| 9 | * This defines a simple but solid secure-computing facility.
|
| 10 | *
|
| 11 | * Mode 1 uses a fixed list of allowed system calls.
|
| 12 | * Mode 2 allows user-defined system call filters in the form
|
| 13 | * of Berkeley Packet Filters/Linux Socket Filters.
|
| 14 |
|
| 15 |
|
| 16 | #include <linux/atomic.h>
|
| 17 | #include <linux/audit.h>
|
| 18 | #include <linux/compat.h>
|
| 19 | #include <linux/sched.h>
|
| 20 | #include <linux/seccomp.h>
|
| 21 | #include <linux/slab.h>
|
| 22 | #include <linux/syscalls.h>
|
| 23 |
|
| 24 | #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
|
| 25 | #include <asm/syscall.h>
|
| 26 | #endif
|
| 27 |
|
| 28 | #ifdef CONFIG_SECCOMP_FILTER
|
| 29 | #include <linux/filter.h>
|
| 30 | #include <linux/pid.h>
|
| 31 | #include <linux/ptrace.h>
|
| 32 | #include <linux/security.h>
|
| 33 | #include <linux/tracehook.h>
|
| 34 | #include <linux/uaccess.h>
|
| 35 |
|
| 36 | |
| 37 | * struct seccomp_filter - container for seccomp BPF programs
|
| 38 | *
|
| 39 | * @usage: reference count to manage the object lifetime.
|
| 40 | * get/put helpers should be used when accessing an instance
|
| 41 | * outside of a lifetime-guarded section. In general, this
|
| 42 | * is only needed for handling filters shared across tasks.
|
| 43 | * @prev: points to a previously installed, or inherited, filter
|
| 44 | * @len: the number of instructions in the program
|
| 45 | * @insnsi: the BPF program instructions to evaluate
|
| 46 | *
|
| 47 | * seccomp_filter objects are organized in a tree linked via the @prev
|
| 48 | * pointer. For any task, it appears to be a singly-linked list starting
|
| 49 | * with current->seccomp.filter, the most recently attached or inherited filter.
|
| 50 | * However, multiple filters may share a @prev node, by way of fork(), which
|
| 51 | * results in a unidirectional tree existing in memory. This is similar to
|
| 52 | * how namespaces work.
|
| 53 | *
|
| 54 | * seccomp_filter objects should never be modified after being attached
|
| 55 | * to a task_struct (other than @usage).
|
| 56 |
|
| 57 | struct seccomp_filter {
|
| 58 | atomic_t usage;
|
| 59 | struct seccomp_filter *prev;
|
| 60 | struct bpf_prog *prog;
|
| 61 | };
|
| 62 |
|
| 63 |
|
| 64 | #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
|
| 65 |
|
| 66 | |
| 67 | * Endianness is explicitly ignored and left for BPF program authors to manage
|
| 68 | * as per the specific architecture.
|
| 69 |
|
| 70 | static void populate_seccomp_data(struct seccomp_data *sd)
|
| 71 | {
|
| 72 | struct task_struct *task = current;
|
| 73 | struct pt_regs *regs = task_pt_regs(task);
|
| 74 | unsigned long args[6];
|
| 75 |
|
| 76 | sd->nr = syscall_get_nr(task, regs);
|
| 77 | sd->arch = syscall_get_arch();
|
| 78 | syscall_get_arguments(task, regs, 0, 6, args);
|
| 79 | sd->args[0] = args[0];
|
| 80 | sd->args[1] = args[1];
|
| 81 | sd->args[2] = args[2];
|
| 82 | sd->args[3] = args[3];
|
| 83 | sd->args[4] = args[4];
|
| 84 | sd->args[5] = args[5];
|
| 85 | sd->instruction_pointer = KSTK_EIP(task);
|
| 86 | }
|
| 87 |
|
| 88 | |
| 89 | * seccomp_check_filter - verify seccomp filter code
|
| 90 | * @filter: filter to verify
|
| 91 | * @flen: length of filter
|
| 92 | *
|
| 93 | * Takes a previously checked filter (by bpf_check_classic) and
|
| 94 | * redirects all filter code that loads struct sk_buff data
|
| 95 | * and related data through seccomp_bpf_load. It also
|
| 96 | * enforces length and alignment checking of those loads.
|
| 97 | *
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| 98 | * Returns 0 if the rule set is legal or -EINVAL if not.
|
| 99 |
|
| 100 | static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
|
| 101 | {
|
| 102 | int pc;
|
| 103 | for (pc = 0; pc < flen; pc++) {
|
| 104 | struct sock_filter *ftest = &filter[pc];
|
| 105 | u16 code = ftest->code;
|
| 106 | u32 k = ftest->k;
|
| 107 |
|
| 108 | switch (code) {
|
| 109 | case BPF_LD | BPF_W | BPF_ABS:
|
| 110 | ftest->code = BPF_LDX | BPF_W | BPF_ABS;
|
| 111 |
|
| 112 | if (k >= sizeof(struct seccomp_data) || k & 3)
|
| 113 | return -EINVAL;
|
| 114 | continue;
|
| 115 | case BPF_LD | BPF_W | BPF_LEN:
|
| 116 | ftest->code = BPF_LD | BPF_IMM;
|
| 117 | ftest->k = sizeof(struct seccomp_data);
|
| 118 | continue;
|
| 119 | case BPF_LDX | BPF_W | BPF_LEN:
|
| 120 | ftest->code = BPF_LDX | BPF_IMM;
|
| 121 | ftest->k = sizeof(struct seccomp_data);
|
| 122 | continue;
|
| 123 |
|
| 124 | case BPF_RET | BPF_K:
|
| 125 | case BPF_RET | BPF_A:
|
| 126 | case BPF_ALU | BPF_ADD | BPF_K:
|
| 127 | case BPF_ALU | BPF_ADD | BPF_X:
|
| 128 | case BPF_ALU | BPF_SUB | BPF_K:
|
| 129 | case BPF_ALU | BPF_SUB | BPF_X:
|
| 130 | case BPF_ALU | BPF_MUL | BPF_K:
|
| 131 | case BPF_ALU | BPF_MUL | BPF_X:
|
| 132 | case BPF_ALU | BPF_DIV | BPF_K:
|
| 133 | case BPF_ALU | BPF_DIV | BPF_X:
|
| 134 | case BPF_ALU | BPF_AND | BPF_K:
|
| 135 | case BPF_ALU | BPF_AND | BPF_X:
|
| 136 | case BPF_ALU | BPF_OR | BPF_K:
|
| 137 | case BPF_ALU | BPF_OR | BPF_X:
|
| 138 | case BPF_ALU | BPF_XOR | BPF_K:
|
| 139 | case BPF_ALU | BPF_XOR | BPF_X:
|
| 140 | case BPF_ALU | BPF_LSH | BPF_K:
|
| 141 | case BPF_ALU | BPF_LSH | BPF_X:
|
| 142 | case BPF_ALU | BPF_RSH | BPF_K:
|
| 143 | case BPF_ALU | BPF_RSH | BPF_X:
|
| 144 | case BPF_ALU | BPF_NEG:
|
| 145 | case BPF_LD | BPF_IMM:
|
| 146 | case BPF_LDX | BPF_IMM:
|
| 147 | case BPF_MISC | BPF_TAX:
|
| 148 | case BPF_MISC | BPF_TXA:
|
| 149 | case BPF_LD | BPF_MEM:
|
| 150 | case BPF_LDX | BPF_MEM:
|
| 151 | case BPF_ST:
|
| 152 | case BPF_STX:
|
| 153 | case BPF_JMP | BPF_JA:
|
| 154 | case BPF_JMP | BPF_JEQ | BPF_K:
|
| 155 | case BPF_JMP | BPF_JEQ | BPF_X:
|
| 156 | case BPF_JMP | BPF_JGE | BPF_K:
|
| 157 | case BPF_JMP | BPF_JGE | BPF_X:
|
| 158 | case BPF_JMP | BPF_JGT | BPF_K:
|
| 159 | case BPF_JMP | BPF_JGT | BPF_X:
|
| 160 | case BPF_JMP | BPF_JSET | BPF_K:
|
| 161 | case BPF_JMP | BPF_JSET | BPF_X:
|
| 162 | continue;
|
| 163 | default:
|
| 164 | return -EINVAL;
|
| 165 | }
|
| 166 | }
|
| 167 | return 0;
|
| 168 | }
|
| 169 |
|
| 170 | |
| 171 | * seccomp_run_filters - evaluates all seccomp filters against @syscall
|
| 172 | * @syscall: number of the current system call
|
| 173 | *
|
| 174 | * Returns valid seccomp BPF response codes.
|
| 175 |
|
| 176 | static u32 seccomp_run_filters(struct seccomp_data *sd)
|
| 177 | {
|
| 178 | struct seccomp_data sd_local;
|
| 179 | u32 ret = SECCOMP_RET_ALLOW;
|
| 180 |
|
| 181 | struct seccomp_filter *f =
|
| 182 | lockless_dereference(current->seccomp.filter);
|
| 183 |
|
| 184 |
|
| 185 | if (unlikely(WARN_ON(f == NULL)))
|
| 186 | return SECCOMP_RET_KILL;
|
| 187 |
|
| 188 | if (!sd) {
|
| 189 | populate_seccomp_data(&sd_local);
|
| 190 | sd = &sd_local;
|
| 191 | }
|
| 192 |
|
| 193 | |
| 194 | * All filters in the list are evaluated and the lowest BPF return
|
| 195 | * value always takes priority (ignoring the DATA).
|
| 196 |
|
| 197 | for (; f; f = f->prev) {
|
| 198 | u32 cur_ret = BPF_PROG_RUN(f->prog, (void *)sd);
|
| 199 |
|
| 200 | if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
|
| 201 | ret = cur_ret;
|
| 202 | }
|
| 203 | return ret;
|
| 204 | }
|
| 205 | #endif
|
| 206 |
|
| 207 | static inline bool seccomp_may_assign_mode(unsigned long seccomp_mode)
|
| 208 | {
|
| 209 | assert_spin_locked(¤t->sighand->siglock);
|
| 210 |
|
| 211 | if (current->seccomp.mode && current->seccomp.mode != seccomp_mode)
|
| 212 | return false;
|
| 213 |
|
| 214 | return true;
|
| 215 | }
|
| 216 |
|
| 217 | static inline void seccomp_assign_mode(struct task_struct *task,
|
| 218 | unsigned long seccomp_mode)
|
| 219 | {
|
| 220 | assert_spin_locked(&task->sighand->siglock);
|
| 221 |
|
| 222 | task->seccomp.mode = seccomp_mode;
|
| 223 | |
| 224 | * Make sure TIF_SECCOMP cannot be set before the mode (and
|
| 225 | * filter) is set.
|
| 226 |
|
| 227 | smp_mb__before_atomic();
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| 228 | set_tsk_thread_flag(task, TIF_SECCOMP);
|
| 229 | }
|
| 230 |
|
| 231 | #ifdef CONFIG_SECCOMP_FILTER
|
| 232 |
|
| 233 | static int is_ancestor(struct seccomp_filter *parent,
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| 234 | struct seccomp_filter *child)
|
| 235 | {
|
| 236 |
|
| 237 | if (parent == NULL)
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| 238 | return 1;
|
| 239 | for (; child; child = child->prev)
|
| 240 | if (child == parent)
|
| 241 | return 1;
|
| 242 | return 0;
|
| 243 | }
|
| 244 |
|
| 245 | |
| 246 | * seccomp_can_sync_threads: checks if all threads can be synchronized
|
| 247 | *
|
| 248 | * Expects sighand and cred_guard_mutex locks to be held.
|
| 249 | *
|
| 250 | * Returns 0 on success, -ve on error, or the pid of a thread which was
|
| 251 | * either not in the correct seccomp mode or it did not have an ancestral
|
| 252 | * seccomp filter.
|
| 253 |
|
| 254 | static inline pid_t seccomp_can_sync_threads(void)
|
| 255 | {
|
| 256 | struct task_struct *thread, *caller;
|
| 257 |
|
| 258 | BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
|
| 259 | assert_spin_locked(¤t->sighand->siglock);
|
| 260 |
|
| 261 |
|
| 262 | caller = current;
|
| 263 | for_each_thread(caller, thread) {
|
| 264 | pid_t failed;
|
| 265 |
|
| 266 |
|
| 267 | if (thread == caller)
|
| 268 | continue;
|
| 269 |
|
| 270 | if (thread->seccomp.mode == SECCOMP_MODE_DISABLED ||
|
| 271 | (thread->seccomp.mode == SECCOMP_MODE_FILTER &&
|
| 272 | is_ancestor(thread->seccomp.filter,
|
| 273 | caller->seccomp.filter)))
|
| 274 | continue;
|
| 275 |
|
| 276 |
|
| 277 | failed = task_pid_vnr(thread);
|
| 278 |
|
| 279 | if (unlikely(WARN_ON(failed == 0)))
|
| 280 | failed = -ESRCH;
|
| 281 | return failed;
|
| 282 | }
|
| 283 |
|
| 284 | return 0;
|
| 285 | }
|
| 286 |
|
| 287 | |
| 288 | * seccomp_sync_threads: sets all threads to use current's filter
|
| 289 | *
|
| 290 | * Expects sighand and cred_guard_mutex locks to be held, and for
|
| 291 | * seccomp_can_sync_threads() to have returned success already
|
| 292 | * without dropping the locks.
|
| 293 | *
|
| 294 |
|
| 295 | static inline void seccomp_sync_threads(void)
|
| 296 | {
|
| 297 | struct task_struct *thread, *caller;
|
| 298 |
|
| 299 | BUG_ON(!mutex_is_locked(¤t->signal->cred_guard_mutex));
|
| 300 | assert_spin_locked(¤t->sighand->siglock);
|
| 301 |
|
| 302 |
|
| 303 | caller = current;
|
| 304 | for_each_thread(caller, thread) {
|
| 305 |
|
| 306 | if (thread == caller)
|
| 307 | continue;
|
| 308 |
|
| 309 |
|
| 310 | get_seccomp_filter(caller);
|
| 311 | |
| 312 | * Drop the task reference to the shared ancestor since
|
| 313 | * current's path will hold a reference. (This also
|
| 314 | * allows a put before the assignment.)
|
| 315 |
|
| 316 | put_seccomp_filter(thread);
|
| 317 | smp_store_release(&thread->seccomp.filter,
|
| 318 | caller->seccomp.filter);
|
| 319 | |
| 320 | * Opt the other thread into seccomp if needed.
|
| 321 | * As threads are considered to be trust-realm
|
| 322 | * equivalent (see ptrace_may_access), it is safe to
|
| 323 | * allow one thread to transition the other.
|
| 324 |
|
| 325 | if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) {
|
| 326 | |
| 327 | * Don't let an unprivileged task work around
|
| 328 | * the no_new_privs restriction by creating
|
| 329 | * a thread that sets it up, enters seccomp,
|
| 330 | * then dies.
|
| 331 |
|
| 332 | if (task_no_new_privs(caller))
|
| 333 | task_set_no_new_privs(thread);
|
| 334 |
|
| 335 | seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
|
| 336 | }
|
| 337 | }
|
| 338 | }
|
| 339 |
|
| 340 | |
| 341 | * seccomp_prepare_filter: Prepares a seccomp filter for use.
|
| 342 | * @fprog: BPF program to install
|
| 343 | *
|
| 344 | * Returns filter on success or an ERR_PTR on failure.
|
| 345 |
|
| 346 | static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
|
| 347 | {
|
| 348 | struct seccomp_filter *sfilter;
|
| 349 | int ret;
|
| 350 |
|
| 351 | if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
|
| 352 | return ERR_PTR(-EINVAL);
|
| 353 |
|
| 354 | BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
|
| 355 |
|
| 356 | |
| 357 | * Installing a seccomp filter requires that the task has
|
| 358 | * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
|
| 359 | * This avoids scenarios where unprivileged tasks can affect the
|
| 360 | * behavior of privileged children.
|
| 361 |
|
| 362 | if (!task_no_new_privs(current) &&
|
| 363 | security_capable_noaudit(current_cred(), current_user_ns(),
|
| 364 | CAP_SYS_ADMIN) != 0)
|
| 365 | return ERR_PTR(-EACCES);
|
| 366 |
|
| 367 |
|
| 368 | sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
|
| 369 | if (!sfilter)
|
| 370 | return ERR_PTR(-ENOMEM);
|
| 371 |
|
| 372 | ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
|
| 373 | seccomp_check_filter);
|
| 374 | if (ret < 0) {
|
| 375 | kfree(sfilter);
|
| 376 | return ERR_PTR(ret);
|
| 377 | }
|
| 378 |
|
| 379 | atomic_set(&sfilter->usage, 1);
|
| 380 |
|
| 381 | return sfilter;
|
| 382 | }
|
| 383 |
|
| 384 | |
| 385 | * seccomp_prepare_user_filter - prepares a user-supplied sock_fprog
|
| 386 | * @user_filter: pointer to the user data containing a sock_fprog.
|
| 387 | *
|
| 388 | * Returns 0 on success and non-zero otherwise.
|
| 389 |
|
| 390 | static struct seccomp_filter *
|
| 391 | seccomp_prepare_user_filter(const char __user *user_filter)
|
| 392 | {
|
| 393 | struct sock_fprog fprog;
|
| 394 | struct seccomp_filter *filter = ERR_PTR(-EFAULT);
|
| 395 |
|
| 396 | #ifdef CONFIG_COMPAT
|
| 397 | if (is_compat_task()) {
|
| 398 | struct compat_sock_fprog fprog32;
|
| 399 | if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
|
| 400 | goto out;
|
| 401 | fprog.len = fprog32.len;
|
| 402 | fprog.filter = compat_ptr(fprog32.filter);
|
| 403 | } else
|
| 404 | #endif
|
| 405 | if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
|
| 406 | goto out;
|
| 407 | filter = seccomp_prepare_filter(&fprog);
|
| 408 | out:
|
| 409 | return filter;
|
| 410 | }
|
| 411 |
|
| 412 | |
| 413 | * seccomp_attach_filter: validate and attach filter
|
| 414 | * @flags: flags to change filter behavior
|
| 415 | * @filter: seccomp filter to add to the current process
|
| 416 | *
|
| 417 | * Caller must be holding current->sighand->siglock lock.
|
| 418 | *
|
| 419 | * Returns 0 on success, -ve on error.
|
| 420 |
|
| 421 | static long seccomp_attach_filter(unsigned int flags,
|
| 422 | struct seccomp_filter *filter)
|
| 423 | {
|
| 424 | unsigned long total_insns;
|
| 425 | struct seccomp_filter *walker;
|
| 426 |
|
| 427 | assert_spin_locked(¤t->sighand->siglock);
|
| 428 |
|
| 429 |
|
| 430 | total_insns = filter->prog->len;
|
| 431 | for (walker = current->seccomp.filter; walker; walker = walker->prev)
|
| 432 | total_insns += walker->prog->len + 4;
|
| 433 | if (total_insns > MAX_INSNS_PER_PATH)
|
| 434 | return -ENOMEM;
|
| 435 |
|
| 436 |
|
| 437 | if (flags & SECCOMP_FILTER_FLAG_TSYNC) {
|
| 438 | int ret;
|
| 439 |
|
| 440 | ret = seccomp_can_sync_threads();
|
| 441 | if (ret)
|
| 442 | return ret;
|
| 443 | }
|
| 444 |
|
| 445 | |
| 446 | * If there is an existing filter, make it the prev and don't drop its
|
| 447 | * task reference.
|
| 448 |
|
| 449 | filter->prev = current->seccomp.filter;
|
| 450 | current->seccomp.filter = filter;
|
| 451 |
|
| 452 |
|
| 453 | if (flags & SECCOMP_FILTER_FLAG_TSYNC)
|
| 454 | seccomp_sync_threads();
|
| 455 |
|
| 456 | return 0;
|
| 457 | }
|
| 458 |
|
| 459 |
|
| 460 | void get_seccomp_filter(struct task_struct *tsk)
|
| 461 | {
|
| 462 | struct seccomp_filter *orig = tsk->seccomp.filter;
|
| 463 | if (!orig)
|
| 464 | return;
|
| 465 |
|
| 466 | atomic_inc(&orig->usage);
|
| 467 | }
|
| 468 |
|
| 469 | static inline void seccomp_filter_free(struct seccomp_filter *filter)
|
| 470 | {
|
| 471 | if (filter) {
|
| 472 | bpf_prog_free(filter->prog);
|
| 473 | kfree(filter);
|
| 474 | }
|
| 475 | }
|
| 476 |
|
| 477 |
|
| 478 | void put_seccomp_filter(struct task_struct *tsk)
|
| 479 | {
|
| 480 | struct seccomp_filter *orig = tsk->seccomp.filter;
|
| 481 |
|
| 482 | while (orig && atomic_dec_and_test(&orig->usage)) {
|
| 483 | struct seccomp_filter *freeme = orig;
|
| 484 | orig = orig->prev;
|
| 485 | seccomp_filter_free(freeme);
|
| 486 | }
|
| 487 | }
|
| 488 |
|
| 489 | |
| 490 | * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
|
| 491 | * @syscall: syscall number to send to userland
|
| 492 | * @reason: filter-supplied reason code to send to userland (via si_errno)
|
| 493 | *
|
| 494 | * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
|
| 495 |
|
| 496 | static void seccomp_send_sigsys(int syscall, int reason)
|
| 497 | {
|
| 498 | struct siginfo info;
|
| 499 | memset(&info, 0, sizeof(info));
|
| 500 | info.si_signo = SIGSYS;
|
| 501 | info.si_code = SYS_SECCOMP;
|
| 502 | info.si_call_addr = (void __user *)KSTK_EIP(current);
|
| 503 | info.si_errno = reason;
|
| 504 | info.si_arch = syscall_get_arch();
|
| 505 | info.si_syscall = syscall;
|
| 506 | force_sig_info(SIGSYS, &info, current);
|
| 507 | }
|
| 508 | #endif
|
| 509 |
|
| 510 | |
| 511 | * Secure computing mode 1 allows only read/write/exit/sigreturn.
|
| 512 | * To be fully secure this must be combined with rlimit
|
| 513 | * to limit the stack allocations too.
|
| 514 |
|
| 515 | static int mode1_syscalls[] = {
|
| 516 | __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
|
| 517 | 0,
|
| 518 | };
|
| 519 |
|
| 520 | #ifdef CONFIG_COMPAT
|
| 521 | static int mode1_syscalls_32[] = {
|
| 522 | __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
|
| 523 | 0,
|
| 524 | };
|
| 525 | #endif
|
| 526 |
|
| 527 | static void __secure_computing_strict(int this_syscall)
|
| 528 | {
|
| 529 | int *syscall_whitelist = mode1_syscalls;
|
| 530 | #ifdef CONFIG_COMPAT
|
| 531 | if (is_compat_task())
|
| 532 | syscall_whitelist = mode1_syscalls_32;
|
| 533 | #endif
|
| 534 | do {
|
| 535 | if (*syscall_whitelist == this_syscall)
|
| 536 | return;
|
| 537 | } while (*++syscall_whitelist);
|
| 538 |
|
| 539 | #ifdef SECCOMP_DEBUG
|
| 540 | dump_stack();
|
| 541 | #endif
|
| 542 | audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL);
|
| 543 | do_exit(SIGKILL);
|
| 544 | }
|
| 545 |
|
| 546 | #ifndef CONFIG_HAVE_ARCH_SECCOMP_FILTER
|
| 547 | void secure_computing_strict(int this_syscall)
|
| 548 | {
|
| 549 | int mode = current->seccomp.mode;
|
| 550 |
|
| 551 | if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
|
| 552 | unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
|
| 553 | return;
|
| 554 |
|
| 555 | if (mode == SECCOMP_MODE_DISABLED)
|
| 556 | return;
|
| 557 | else if (mode == SECCOMP_MODE_STRICT)
|
| 558 | __secure_computing_strict(this_syscall);
|
| 559 | else
|
| 560 | BUG();
|
| 561 | }
|
| 562 | #else
|
| 563 | int __secure_computing(void)
|
| 564 | {
|
| 565 | u32 phase1_result = seccomp_phase1(NULL);
|
| 566 |
|
| 567 | if (likely(phase1_result == SECCOMP_PHASE1_OK))
|
| 568 | return 0;
|
| 569 | else if (likely(phase1_result == SECCOMP_PHASE1_SKIP))
|
| 570 | return -1;
|
| 571 | else
|
| 572 | return seccomp_phase2(phase1_result);
|
| 573 | }
|
| 574 |
|
| 575 | #ifdef CONFIG_SECCOMP_FILTER
|
| 576 | static u32 __seccomp_phase1_filter(int this_syscall, struct seccomp_data *sd)
|
| 577 | {
|
| 578 | u32 filter_ret, action;
|
| 579 | int data;
|
| 580 |
|
| 581 | |
| 582 | * Make sure that any changes to mode from another thread have
|
| 583 | * been seen after TIF_SECCOMP was seen.
|
| 584 |
|
| 585 | rmb();
|
| 586 |
|
| 587 | filter_ret = seccomp_run_filters(sd);
|
| 588 | data = filter_ret & SECCOMP_RET_DATA;
|
| 589 | action = filter_ret & SECCOMP_RET_ACTION;
|
| 590 |
|
| 591 | switch (action) {
|
| 592 | case SECCOMP_RET_ERRNO:
|
| 593 |
|
| 594 | if (data > MAX_ERRNO)
|
| 595 | data = MAX_ERRNO;
|
| 596 | syscall_set_return_value(current, task_pt_regs(current),
|
| 597 | -data, 0);
|
| 598 | goto skip;
|
| 599 |
|
| 600 | case SECCOMP_RET_TRAP:
|
| 601 |
|
| 602 | syscall_rollback(current, task_pt_regs(current));
|
| 603 |
|
| 604 | seccomp_send_sigsys(this_syscall, data);
|
| 605 | goto skip;
|
| 606 |
|
| 607 | case SECCOMP_RET_TRACE:
|
| 608 | return filter_ret;
|
| 609 |
|
| 610 | case SECCOMP_RET_ALLOW:
|
| 611 | return SECCOMP_PHASE1_OK;
|
| 612 |
|
| 613 | case SECCOMP_RET_KILL:
|
| 614 | default:
|
| 615 | audit_seccomp(this_syscall, SIGSYS, action);
|
| 616 | do_exit(SIGSYS);
|
| 617 | }
|
| 618 |
|
| 619 | unreachable();
|
| 620 |
|
| 621 | skip:
|
| 622 | audit_seccomp(this_syscall, 0, action);
|
| 623 | return SECCOMP_PHASE1_SKIP;
|
| 624 | }
|
| 625 | #endif
|
| 626 |
|
| 627 | |
| 628 | * seccomp_phase1() - run fast path seccomp checks on the current syscall
|
| 629 | * @arg sd: The seccomp_data or NULL
|
| 630 | *
|
| 631 | * This only reads pt_regs via the syscall_xyz helpers. The only change
|
| 632 | * it will make to pt_regs is via syscall_set_return_value, and it will
|
| 633 | * only do that if it returns SECCOMP_PHASE1_SKIP.
|
| 634 | *
|
| 635 | * If sd is provided, it will not read pt_regs at all.
|
| 636 | *
|
| 637 | * It may also call do_exit or force a signal; these actions must be
|
| 638 | * safe.
|
| 639 | *
|
| 640 | * If it returns SECCOMP_PHASE1_OK, the syscall passes checks and should
|
| 641 | * be processed normally.
|
| 642 | *
|
| 643 | * If it returns SECCOMP_PHASE1_SKIP, then the syscall should not be
|
| 644 | * invoked. In this case, seccomp_phase1 will have set the return value
|
| 645 | * using syscall_set_return_value.
|
| 646 | *
|
| 647 | * If it returns anything else, then the return value should be passed
|
| 648 | * to seccomp_phase2 from a context in which ptrace hooks are safe.
|
| 649 |
|
| 650 | u32 seccomp_phase1(struct seccomp_data *sd)
|
| 651 | {
|
| 652 | int mode = current->seccomp.mode;
|
| 653 | int this_syscall = sd ? sd->nr :
|
| 654 | syscall_get_nr(current, task_pt_regs(current));
|
| 655 |
|
| 656 | if (config_enabled(CONFIG_CHECKPOINT_RESTORE) &&
|
| 657 | unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
|
| 658 | return SECCOMP_PHASE1_OK;
|
| 659 |
|
| 660 | switch (mode) {
|
| 661 | case SECCOMP_MODE_STRICT:
|
| 662 | __secure_computing_strict(this_syscall);
|
| 663 | return SECCOMP_PHASE1_OK;
|
| 664 | #ifdef CONFIG_SECCOMP_FILTER
|
| 665 | case SECCOMP_MODE_FILTER:
|
| 666 | return __seccomp_phase1_filter(this_syscall, sd);
|
| 667 | #endif
|
| 668 | default:
|
| 669 | BUG();
|
| 670 | }
|
| 671 | }
|
| 672 |
|
| 673 | |
| 674 | * seccomp_phase2() - finish slow path seccomp work for the current syscall
|
| 675 | * @phase1_result: The return value from seccomp_phase1()
|
| 676 | *
|
| 677 | * This must be called from a context in which ptrace hooks can be used.
|
| 678 | *
|
| 679 | * Returns 0 if the syscall should be processed or -1 to skip the syscall.
|
| 680 |
|
| 681 | int seccomp_phase2(u32 phase1_result)
|
| 682 | {
|
| 683 | struct pt_regs *regs = task_pt_regs(current);
|
| 684 | u32 action = phase1_result & SECCOMP_RET_ACTION;
|
| 685 | int data = phase1_result & SECCOMP_RET_DATA;
|
| 686 |
|
| 687 | BUG_ON(action != SECCOMP_RET_TRACE);
|
| 688 |
|
| 689 | audit_seccomp(syscall_get_nr(current, regs), 0, action);
|
| 690 |
|
| 691 |
|
| 692 | if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
|
| 693 | syscall_set_return_value(current, regs,
|
| 694 | -ENOSYS, 0);
|
| 695 | return -1;
|
| 696 | }
|
| 697 |
|
| 698 |
|
| 699 | ptrace_event(PTRACE_EVENT_SECCOMP, data);
|
| 700 | |
| 701 | * The delivery of a fatal signal during event
|
| 702 | * notification may silently skip tracer notification.
|
| 703 | * Terminating the task now avoids executing a system
|
| 704 | * call that may not be intended.
|
| 705 |
|
| 706 | if (fatal_signal_pending(current))
|
| 707 | do_exit(SIGSYS);
|
| 708 | if (syscall_get_nr(current, regs) < 0)
|
| 709 | return -1;
|
| 710 |
|
| 711 | return 0;
|
| 712 | }
|
| 713 | #endif
|
| 714 |
|
| 715 | long prctl_get_seccomp(void)
|
| 716 | {
|
| 717 | return current->seccomp.mode;
|
| 718 | }
|
| 719 |
|
| 720 | |
| 721 | * seccomp_set_mode_strict: internal function for setting strict seccomp
|
| 722 | *
|
| 723 | * Once current->seccomp.mode is non-zero, it may not be changed.
|
| 724 | *
|
| 725 | * Returns 0 on success or -EINVAL on failure.
|
| 726 |
|
| 727 | static long seccomp_set_mode_strict(void)
|
| 728 | {
|
| 729 | const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
|
| 730 | long ret = -EINVAL;
|
| 731 |
|
| 732 | spin_lock_irq(¤t->sighand->siglock);
|
| 733 |
|
| 734 | if (!seccomp_may_assign_mode(seccomp_mode))
|
| 735 | goto out;
|
| 736 |
|
| 737 | #ifdef TIF_NOTSC
|
| 738 | disable_TSC();
|
| 739 | #endif
|
| 740 | seccomp_assign_mode(current, seccomp_mode);
|
| 741 | ret = 0;
|
| 742 |
|
| 743 | out:
|
| 744 | spin_unlock_irq(¤t->sighand->siglock);
|
| 745 |
|
| 746 | return ret;
|
| 747 | }
|
| 748 |
|
| 749 | #ifdef CONFIG_SECCOMP_FILTER
|
| 750 | |
| 751 | * seccomp_set_mode_filter: internal function for setting seccomp filter
|
| 752 | * @flags: flags to change filter behavior
|
| 753 | * @filter: struct sock_fprog containing filter
|
| 754 | *
|
| 755 | * This function may be called repeatedly to install additional filters.
|
| 756 | * Every filter successfully installed will be evaluated (in reverse order)
|
| 757 | * for each system call the task makes.
|
| 758 | *
|
| 759 | * Once current->seccomp.mode is non-zero, it may not be changed.
|
| 760 | *
|
| 761 | * Returns 0 on success or -EINVAL on failure.
|
| 762 |
|
| 763 | static long seccomp_set_mode_filter(unsigned int flags,
|
| 764 | const char __user *filter)
|
| 765 | {
|
| 766 | const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
|
| 767 | struct seccomp_filter *prepared = NULL;
|
| 768 | long ret = -EINVAL;
|
| 769 |
|
| 770 |
|
| 771 | if (flags & ~SECCOMP_FILTER_FLAG_MASK)
|
| 772 | return -EINVAL;
|
| 773 |
|
| 774 |
|
| 775 | prepared = seccomp_prepare_user_filter(filter);
|
| 776 | if (IS_ERR(prepared))
|
| 777 | return PTR_ERR(prepared);
|
| 778 |
|
| 779 | |
| 780 | * Make sure we cannot change seccomp or nnp state via TSYNC
|
| 781 | * while another thread is in the middle of calling exec.
|
| 782 |
|
| 783 | if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
|
| 784 | mutex_lock_killable(¤t->signal->cred_guard_mutex))
|
| 785 | goto out_free;
|
| 786 |
|
| 787 | spin_lock_irq(¤t->sighand->siglock);
|
| 788 |
|
| 789 | if (!seccomp_may_assign_mode(seccomp_mode))
|
| 790 | goto out;
|
| 791 |
|
| 792 | ret = seccomp_attach_filter(flags, prepared);
|
| 793 | if (ret)
|
| 794 | goto out;
|
| 795 |
|
| 796 | prepared = NULL;
|
| 797 |
|
| 798 | seccomp_assign_mode(current, seccomp_mode);
|
| 799 | out:
|
| 800 | spin_unlock_irq(¤t->sighand->siglock);
|
| 801 | if (flags & SECCOMP_FILTER_FLAG_TSYNC)
|
| 802 | mutex_unlock(¤t->signal->cred_guard_mutex);
|
| 803 | out_free:
|
| 804 | seccomp_filter_free(prepared);
|
| 805 | return ret;
|
| 806 | }
|
| 807 | #else
|
| 808 | static inline long seccomp_set_mode_filter(unsigned int flags,
|
| 809 | const char __user *filter)
|
| 810 | {
|
| 811 | return -EINVAL;
|
| 812 | }
|
| 813 | #endif
|
| 814 |
|
| 815 |
|
| 816 | static long do_seccomp(unsigned int op, unsigned int flags,
|
| 817 | const char __user *uargs)
|
| 818 | {
|
| 819 | switch (op) {
|
| 820 | case SECCOMP_SET_MODE_STRICT:
|
| 821 | if (flags != 0 || uargs != NULL)
|
| 822 | return -EINVAL;
|
| 823 | return seccomp_set_mode_strict();
|
| 824 | case SECCOMP_SET_MODE_FILTER:
|
| 825 | return seccomp_set_mode_filter(flags, uargs);
|
| 826 | default:
|
| 827 | return -EINVAL;
|
| 828 | }
|
| 829 | }
|
| 830 |
|
| 831 | SYSCALL_DEFINE3(seccomp, unsigned int, op, unsigned int, flags,
|
| 832 | const char __user *, uargs)
|
| 833 | {
|
| 834 | return do_seccomp(op, flags, uargs);
|
| 835 | }
|
| 836 |
|
| 837 | |
| 838 | * prctl_set_seccomp: configures current->seccomp.mode
|
| 839 | * @seccomp_mode: requested mode to use
|
| 840 | * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
|
| 841 | *
|
| 842 | * Returns 0 on success or -EINVAL on failure.
|
| 843 |
|
| 844 | long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
|
| 845 | {
|
| 846 | unsigned int op;
|
| 847 | char __user *uargs;
|
| 848 |
|
| 849 | switch (seccomp_mode) {
|
| 850 | case SECCOMP_MODE_STRICT:
|
| 851 | op = SECCOMP_SET_MODE_STRICT;
|
| 852 | |
| 853 | * Setting strict mode through prctl always ignored filter,
|
| 854 | * so make sure it is always NULL here to pass the internal
|
| 855 | * check in do_seccomp().
|
| 856 |
|
| 857 | uargs = NULL;
|
| 858 | break;
|
| 859 | case SECCOMP_MODE_FILTER:
|
| 860 | op = SECCOMP_SET_MODE_FILTER;
|
| 861 | uargs = filter;
|
| 862 | break;
|
| 863 | default:
|
| 864 | return -EINVAL;
|
| 865 | }
|
| 866 |
|
| 867 |
|
| 868 | return do_seccomp(op, 0, uargs);
|
| 869 | }
|