| 1 | |
| 2 | * linux/kernel/seccomp.c
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| 3 | *
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| 4 | * Copyright 2004-2005 Andrea Arcangeli <[email protected]>
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| 5 | *
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| 6 | * This defines a simple but solid secure-computing mode.
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| 7 |
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| 8 |
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| 9 | #include <linux/seccomp.h>
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| 10 | #include <linux/sched.h>
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| 11 | #include <linux/compat.h>
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| 12 |
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| 13 |
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| 14 | #define NR_SECCOMP_MODES 1
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| 15 |
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| 16 | |
| 17 | * Secure computing mode 1 allows only read/write/exit/sigreturn.
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| 18 | * To be fully secure this must be combined with rlimit
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| 19 | * to limit the stack allocations too.
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| 20 |
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| 21 | static int mode1_syscalls[] = {
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| 22 | __NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
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| 23 | 0,
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| 24 | };
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| 25 |
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| 26 | #ifdef CONFIG_COMPAT
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| 27 | static int mode1_syscalls_32[] = {
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| 28 | __NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
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| 29 | 0,
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| 30 | };
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| 31 | #endif
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| 32 |
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| 33 | void __secure_computing(int this_syscall)
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| 34 | {
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| 35 | int mode = current->seccomp.mode;
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| 36 | int * syscall;
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| 37 |
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| 38 | switch (mode) {
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| 39 | case 1:
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| 40 | syscall = mode1_syscalls;
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| 41 | #ifdef CONFIG_COMPAT
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| 42 | if (is_compat_task())
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| 43 | syscall = mode1_syscalls_32;
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| 44 | #endif
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| 45 | do {
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| 46 | if (*syscall == this_syscall)
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| 47 | return;
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| 48 | } while (*++syscall);
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| 49 | break;
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| 50 | default:
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| 51 | BUG();
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| 52 | }
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| 53 |
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| 54 | #ifdef SECCOMP_DEBUG
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| 55 | dump_stack();
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| 56 | #endif
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| 57 | do_exit(SIGKILL);
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| 58 | }
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| 59 |
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| 60 | long prctl_get_seccomp(void)
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| 61 | {
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| 62 | return current->seccomp.mode;
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| 63 | }
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| 64 |
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| 65 | long prctl_set_seccomp(unsigned long seccomp_mode)
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| 66 | {
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| 67 | long ret;
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| 68 |
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| 69 |
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| 70 | ret = -EPERM;
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| 71 | if (unlikely(current->seccomp.mode))
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| 72 | goto out;
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| 73 |
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| 74 | ret = -EINVAL;
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| 75 | if (seccomp_mode && seccomp_mode <= NR_SECCOMP_MODES) {
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| 76 | current->seccomp.mode = seccomp_mode;
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| 77 | set_thread_flag(TIF_SECCOMP);
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| 78 | #ifdef TIF_NOTSC
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| 79 | disable_TSC();
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| 80 | #endif
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| 81 | ret = 0;
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| 82 | }
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| 83 |
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| 84 | out:
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| 85 | return ret;
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| 86 | }
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