kernel/seccomp.c

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