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
3 // found in the LICENSE file.
4
5 #include "sandbox/linux/seccomp-bpf/die.h"
6
7 #include <errno.h>
8 #include <signal.h>
9 #include <stdio.h>
10 #include <sys/prctl.h>
11 #include <sys/syscall.h>
12 #include <unistd.h>
13
14 #include <string>
15
16 #include "base/logging.h"
17 #include "base/posix/eintr_wrapper.h"
18 #include "sandbox/linux/seccomp-bpf/syscall.h"
19 #include "sandbox/linux/services/syscall_wrappers.h"
20 #include "sandbox/linux/system_headers/linux_signal.h"
21
22 namespace sandbox {
23
ExitGroup()24 void Die::ExitGroup() {
25 // exit_group() should exit our program. After all, it is defined as a
26 // function that doesn't return. But things can theoretically go wrong.
27 // Especially, since we are dealing with system call filters. Continuing
28 // execution would be very bad in most cases where ExitGroup() gets called.
29 // So, we'll try a few other strategies too.
30 Syscall::Call(__NR_exit_group, 1);
31
32 // We have no idea what our run-time environment looks like. So, signal
33 // handlers might or might not do the right thing. Try to reset settings
34 // to a defined state; but we have not way to verify whether we actually
35 // succeeded in doing so. Nonetheless, triggering a fatal signal could help
36 // us terminate.
37 struct sigaction sa = {};
38 sa.sa_handler = LINUX_SIG_DFL;
39 sa.sa_flags = LINUX_SA_RESTART;
40 sys_sigaction(LINUX_SIGSEGV, &sa, nullptr);
41 Syscall::Call(__NR_prctl, PR_SET_DUMPABLE, (void*)0, (void*)0, (void*)0);
42 if (*(volatile char*)0) {
43 }
44
45 // If there is no way for us to ask for the program to exit, the next
46 // best thing we can do is to loop indefinitely. Maybe, somebody will notice
47 // and file a bug...
48 // We in fact retry the system call inside of our loop so that it will
49 // stand out when somebody tries to diagnose the problem by using "strace".
50 for (;;) {
51 Syscall::Call(__NR_exit_group, 1);
52 }
53 }
54
SandboxDie(const char * msg,const char * file,int line)55 void Die::SandboxDie(const char* msg, const char* file, int line) {
56 if (simple_exit_) {
57 LogToStderr(msg, file, line);
58 } else {
59 logging::LogMessage(file, line, logging::LOG_FATAL).stream() << msg;
60 }
61 ExitGroup();
62 }
63
RawSandboxDie(const char * msg)64 void Die::RawSandboxDie(const char* msg) {
65 if (!msg)
66 msg = "";
67 RAW_LOG(FATAL, msg);
68 ExitGroup();
69 }
70
SandboxInfo(const char * msg,const char * file,int line)71 void Die::SandboxInfo(const char* msg, const char* file, int line) {
72 if (!suppress_info_) {
73 logging::LogMessage(file, line, logging::LOG_INFO).stream() << msg;
74 }
75 }
76
LogToStderr(const char * msg,const char * file,int line)77 void Die::LogToStderr(const char* msg, const char* file, int line) {
78 if (msg) {
79 char buf[40];
80 snprintf(buf, sizeof(buf), "%d", line);
81 std::string s = std::string(file) + ":" + buf + ":" + msg + "\n";
82
83 // No need to loop. Short write()s are unlikely and if they happen we
84 // probably prefer them over a loop that blocks.
85 ignore_result(
86 HANDLE_EINTR(Syscall::Call(__NR_write, 2, s.c_str(), s.length())));
87 }
88 }
89
90 bool Die::simple_exit_ = false;
91 bool Die::suppress_info_ = false;
92
93 } // namespace sandbox
94