OLD | NEW |
1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h" | 5 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h" |
6 | 6 |
7 // Some headers on Android are missing cdefs: crbug.com/172337. | 7 // Some headers on Android are missing cdefs: crbug.com/172337. |
8 // (We can't use OS_ANDROID here since build_config.h is not included). | 8 // (We can't use OS_ANDROID here since build_config.h is not included). |
9 #if defined(ANDROID) | 9 #if defined(ANDROID) |
10 #include <sys/cdefs.h> | 10 #include <sys/cdefs.h> |
(...skipping 41 matching lines...) Expand 10 before | Expand all | Expand 10 after Loading... |
52 bool KernelSupportsSeccompBPF() { | 52 bool KernelSupportsSeccompBPF() { |
53 errno = 0; | 53 errno = 0; |
54 const int rv = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, nullptr); | 54 const int rv = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, nullptr); |
55 | 55 |
56 if (rv == -1 && EFAULT == errno) { | 56 if (rv == -1 && EFAULT == errno) { |
57 return true; | 57 return true; |
58 } | 58 } |
59 return false; | 59 return false; |
60 } | 60 } |
61 | 61 |
| 62 // LG introduced a buggy syscall, sys_set_media_ext, with the same number as |
| 63 // seccomp. Return true if the current kernel has this buggy syscall. |
| 64 // |
| 65 // We want this to work with upcoming versions of seccomp, so we pass bogus |
| 66 // flags that are unlikely to ever be used by the kernel. A normal kernel would |
| 67 // return -EINVAL, but a buggy LG kernel would return 1. |
| 68 bool KernelHasLGBug() { |
| 69 #if defined(OS_ANDROID) |
| 70 // sys_set_media will see this as NULL, which should be a safe (non-crashing) |
| 71 // way to invoke it. A genuine seccomp syscall will see it as |
| 72 // SECCOMP_SET_MODE_STRICT. |
| 73 const unsigned int operation = 0; |
| 74 // Chosen by fair dice roll. Guaranteed to be random. |
| 75 const unsigned int flags = 0xf7a46a5c; |
| 76 const int rv = sys_seccomp(operation, flags, nullptr); |
| 77 // A genuine kernel would return -EINVAL (which would set rv to -1 and errno |
| 78 // to EINVAL), or at the very least return some kind of error (which would |
| 79 // set rv to -1). Any other behavior indicates that whatever code received |
| 80 // our syscall was not the real seccomp. |
| 81 if (rv != -1) { |
| 82 return true; |
| 83 } |
| 84 #endif // defined(OS_ANDROID) |
| 85 |
| 86 return false; |
| 87 } |
| 88 |
62 // Check if the kernel supports seccomp-filter via the seccomp system call | 89 // Check if the kernel supports seccomp-filter via the seccomp system call |
63 // and the TSYNC feature to enable seccomp on all threads. | 90 // and the TSYNC feature to enable seccomp on all threads. |
64 bool KernelSupportsSeccompTsync() { | 91 bool KernelSupportsSeccompTsync() { |
| 92 if (KernelHasLGBug()) { |
| 93 return false; |
| 94 } |
| 95 |
65 errno = 0; | 96 errno = 0; |
66 const int rv = | 97 const int rv = |
67 sys_seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_TSYNC, nullptr); | 98 sys_seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_TSYNC, nullptr); |
68 | 99 |
69 if (rv == -1 && errno == EFAULT) { | 100 if (rv == -1 && errno == EFAULT) { |
70 return true; | 101 return true; |
71 } else { | 102 } else { |
72 // TODO(jln): turn these into DCHECK after 417888 is considered fixed. | 103 // TODO(jln): turn these into DCHECK after 417888 is considered fixed. |
73 CHECK_EQ(-1, rv); | 104 CHECK_EQ(-1, rv); |
74 CHECK(ENOSYS == errno || EINVAL == errno); | 105 CHECK(ENOSYS == errno || EINVAL == errno); |
(...skipping 164 matching lines...) Expand 10 before | Expand all | Expand 10 after Loading... |
239 } else { | 270 } else { |
240 if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) { | 271 if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) { |
241 SANDBOX_DIE("Kernel refuses to turn on BPF filters"); | 272 SANDBOX_DIE("Kernel refuses to turn on BPF filters"); |
242 } | 273 } |
243 } | 274 } |
244 | 275 |
245 sandbox_has_started_ = true; | 276 sandbox_has_started_ = true; |
246 } | 277 } |
247 | 278 |
248 } // namespace sandbox | 279 } // namespace sandbox |
OLD | NEW |