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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 01:47:29 +0000 |
commit | 0ebf5bdf043a27fd3dfb7f92e0cb63d88954c44d (patch) | |
tree | a31f07c9bcca9d56ce61e9a1ffd30ef350d513aa /tools/fuzzing/libfuzzer/FuzzerUtilDarwin.cpp | |
parent | Initial commit. (diff) | |
download | firefox-esr-upstream/115.8.0esr.tar.xz firefox-esr-upstream/115.8.0esr.zip |
Adding upstream version 115.8.0esr.upstream/115.8.0esr
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | tools/fuzzing/libfuzzer/FuzzerUtilDarwin.cpp | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/tools/fuzzing/libfuzzer/FuzzerUtilDarwin.cpp b/tools/fuzzing/libfuzzer/FuzzerUtilDarwin.cpp new file mode 100644 index 0000000000..a5bed658a4 --- /dev/null +++ b/tools/fuzzing/libfuzzer/FuzzerUtilDarwin.cpp @@ -0,0 +1,170 @@ +//===- FuzzerUtilDarwin.cpp - Misc utils ----------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// Misc utils for Darwin. +//===----------------------------------------------------------------------===// +#include "FuzzerPlatform.h" +#if LIBFUZZER_APPLE +#include "FuzzerCommand.h" +#include "FuzzerIO.h" +#include <mutex> +#include <signal.h> +#include <spawn.h> +#include <stdlib.h> +#include <string.h> +#include <sys/wait.h> +#include <unistd.h> + +// There is no header for this on macOS so declare here +extern "C" char **environ; + +namespace fuzzer { + +static std::mutex SignalMutex; +// Global variables used to keep track of how signal handling should be +// restored. They should **not** be accessed without holding `SignalMutex`. +static int ActiveThreadCount = 0; +static struct sigaction OldSigIntAction; +static struct sigaction OldSigQuitAction; +static sigset_t OldBlockedSignalsSet; + +// This is a reimplementation of Libc's `system()`. On Darwin the Libc +// implementation contains a mutex which prevents it from being used +// concurrently. This implementation **can** be used concurrently. It sets the +// signal handlers when the first thread enters and restores them when the last +// thread finishes execution of the function and ensures this is not racey by +// using a mutex. +int ExecuteCommand(const Command &Cmd) { + std::string CmdLine = Cmd.toString(); + posix_spawnattr_t SpawnAttributes; + if (posix_spawnattr_init(&SpawnAttributes)) + return -1; + // Block and ignore signals of the current process when the first thread + // enters. + { + std::lock_guard<std::mutex> Lock(SignalMutex); + if (ActiveThreadCount == 0) { + static struct sigaction IgnoreSignalAction; + sigset_t BlockedSignalsSet; + memset(&IgnoreSignalAction, 0, sizeof(IgnoreSignalAction)); + IgnoreSignalAction.sa_handler = SIG_IGN; + + if (sigaction(SIGINT, &IgnoreSignalAction, &OldSigIntAction) == -1) { + Printf("Failed to ignore SIGINT\n"); + (void)posix_spawnattr_destroy(&SpawnAttributes); + return -1; + } + if (sigaction(SIGQUIT, &IgnoreSignalAction, &OldSigQuitAction) == -1) { + Printf("Failed to ignore SIGQUIT\n"); + // Try our best to restore the signal handlers. + (void)sigaction(SIGINT, &OldSigIntAction, NULL); + (void)posix_spawnattr_destroy(&SpawnAttributes); + return -1; + } + + (void)sigemptyset(&BlockedSignalsSet); + (void)sigaddset(&BlockedSignalsSet, SIGCHLD); + if (sigprocmask(SIG_BLOCK, &BlockedSignalsSet, &OldBlockedSignalsSet) == + -1) { + Printf("Failed to block SIGCHLD\n"); + // Try our best to restore the signal handlers. + (void)sigaction(SIGQUIT, &OldSigQuitAction, NULL); + (void)sigaction(SIGINT, &OldSigIntAction, NULL); + (void)posix_spawnattr_destroy(&SpawnAttributes); + return -1; + } + } + ++ActiveThreadCount; + } + + // NOTE: Do not introduce any new `return` statements past this + // point. It is important that `ActiveThreadCount` always be decremented + // when leaving this function. + + // Make sure the child process uses the default handlers for the + // following signals rather than inheriting what the parent has. + sigset_t DefaultSigSet; + (void)sigemptyset(&DefaultSigSet); + (void)sigaddset(&DefaultSigSet, SIGQUIT); + (void)sigaddset(&DefaultSigSet, SIGINT); + (void)posix_spawnattr_setsigdefault(&SpawnAttributes, &DefaultSigSet); + // Make sure the child process doesn't block SIGCHLD + (void)posix_spawnattr_setsigmask(&SpawnAttributes, &OldBlockedSignalsSet); + short SpawnFlags = POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK; + (void)posix_spawnattr_setflags(&SpawnAttributes, SpawnFlags); + + pid_t Pid; + char **Environ = environ; // Read from global + const char *CommandCStr = CmdLine.c_str(); + char *const Argv[] = { + strdup("sh"), + strdup("-c"), + strdup(CommandCStr), + NULL + }; + int ErrorCode = 0, ProcessStatus = 0; + // FIXME: We probably shouldn't hardcode the shell path. + ErrorCode = posix_spawn(&Pid, "/bin/sh", NULL, &SpawnAttributes, + Argv, Environ); + (void)posix_spawnattr_destroy(&SpawnAttributes); + if (!ErrorCode) { + pid_t SavedPid = Pid; + do { + // Repeat until call completes uninterrupted. + Pid = waitpid(SavedPid, &ProcessStatus, /*options=*/0); + } while (Pid == -1 && errno == EINTR); + if (Pid == -1) { + // Fail for some other reason. + ProcessStatus = -1; + } + } else if (ErrorCode == ENOMEM || ErrorCode == EAGAIN) { + // Fork failure. + ProcessStatus = -1; + } else { + // Shell execution failure. + ProcessStatus = W_EXITCODE(127, 0); + } + for (unsigned i = 0, n = sizeof(Argv) / sizeof(Argv[0]); i < n; ++i) + free(Argv[i]); + + // Restore the signal handlers of the current process when the last thread + // using this function finishes. + { + std::lock_guard<std::mutex> Lock(SignalMutex); + --ActiveThreadCount; + if (ActiveThreadCount == 0) { + bool FailedRestore = false; + if (sigaction(SIGINT, &OldSigIntAction, NULL) == -1) { + Printf("Failed to restore SIGINT handling\n"); + FailedRestore = true; + } + if (sigaction(SIGQUIT, &OldSigQuitAction, NULL) == -1) { + Printf("Failed to restore SIGQUIT handling\n"); + FailedRestore = true; + } + if (sigprocmask(SIG_BLOCK, &OldBlockedSignalsSet, NULL) == -1) { + Printf("Failed to unblock SIGCHLD\n"); + FailedRestore = true; + } + if (FailedRestore) + ProcessStatus = -1; + } + } + return ProcessStatus; +} + +void DiscardOutput(int Fd) { + FILE* Temp = fopen("/dev/null", "w"); + if (!Temp) + return; + dup2(fileno(Temp), Fd); + fclose(Temp); +} + +} // namespace fuzzer + +#endif // LIBFUZZER_APPLE |