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Stop the child output reading when the child process ends. #1712

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81 changes: 49 additions & 32 deletions fuzztest/internal/subprocess.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,8 @@
#include <fcntl.h>
#include <poll.h>
#include <spawn.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#endif // !defined(_MSC_VER)
Expand Down Expand Up @@ -64,9 +66,9 @@ class SubProcess {
absl::Duration timeout);

private:
void CreatePipes();
void CloseChildPipes();
void CloseParentPipes();
void CreateCommunicationFds();
void CloseChildFds();
void CloseParentFds();
posix_spawn_file_actions_t CreateChildFileActions();
void StartWatchdog(absl::Duration timeout);
pid_t StartChild(
Expand All @@ -77,36 +79,41 @@ class SubProcess {
// Pipe file descriptors pairs. Index 0 is for stdout, index 1 is for stderr.
static constexpr int kStdOutIdx = 0;
static constexpr int kStdErrIdx = 1;
int parent_pipe_[2];
int child_pipe_[2];
int parent_fds_[2];
int child_fds_[2];
};

// Creates parent/child pipes for piping stdout/stderr from child to parent.
void SubProcess::CreatePipes() {
// Creates communication fds for passing through stdout/stderr from child to
// parent.
void SubProcess::CreateCommunicationFds() {
for (int channel : {kStdOutIdx, kStdErrIdx}) {
int pipe_fds[2];
FUZZTEST_INTERNAL_CHECK(pipe(pipe_fds) == 0,
"Cannot create pipe: ", strerror(errno));
int fds[2];
FUZZTEST_INTERNAL_CHECK(socketpair(AF_UNIX, SOCK_STREAM, 0, fds) == 0,
"Cannot create socketpair: ", strerror(errno));

parent_pipe_[channel] = pipe_fds[0];
child_pipe_[channel] = pipe_fds[1];
parent_fds_[channel] = fds[0];
child_fds_[channel] = fds[1];
FUZZTEST_INTERNAL_CHECK(shutdown(fds[0], SHUT_WR) == 0,
"Cannot shutdown fds: ", strerror(errno));
FUZZTEST_INTERNAL_CHECK(shutdown(fds[1], SHUT_RD) == 0,
"Cannot shutdown fds: ", strerror(errno));

FUZZTEST_INTERNAL_CHECK(
fcntl(parent_pipe_[channel], F_SETFL, O_NONBLOCK) != -1,
"Cannot make pipe non-blocking: ", strerror(errno));
fcntl(parent_fds_[channel], F_SETFL, O_NONBLOCK) != -1,
"Cannot make communication fds non-blocking: ", strerror(errno));
}
}

void SubProcess::CloseChildPipes() {
void SubProcess::CloseChildFds() {
for (int channel : {kStdOutIdx, kStdErrIdx}) {
FUZZTEST_INTERNAL_CHECK(close(child_pipe_[channel]) != -1,
FUZZTEST_INTERNAL_CHECK(close(child_fds_[channel]) != -1,
"Cannot close pipe: ", strerror(errno));
}
}

void SubProcess::CloseParentPipes() {
void SubProcess::CloseParentFds() {
for (int channel : {kStdOutIdx, kStdErrIdx}) {
FUZZTEST_INTERNAL_CHECK(close(parent_pipe_[channel]) != -1,
FUZZTEST_INTERNAL_CHECK(close(parent_fds_[channel]) != -1,
"Cannot close pipe: ", strerror(errno));
}
}
Expand All @@ -128,16 +135,16 @@ posix_spawn_file_actions_t SubProcess::CreateChildFileActions() {

for (int channel : {kStdOutIdx, kStdErrIdx}) {
// Close parent-side pipes.
err = posix_spawn_file_actions_addclose(&actions, parent_pipe_[channel]);
err = posix_spawn_file_actions_addclose(&actions, parent_fds_[channel]);
FUZZTEST_INTERNAL_CHECK(err == 0,
"Cannot add close() action: ", strerror(err));

// Replace stdout/stderr file descriptors with the pipes.
int fd = channel == kStdOutIdx ? STDOUT_FILENO : STDERR_FILENO;
err = posix_spawn_file_actions_adddup2(&actions, child_pipe_[channel], fd);
err = posix_spawn_file_actions_adddup2(&actions, child_fds_[channel], fd);
FUZZTEST_INTERNAL_CHECK(err == 0,
"Cannot add dup2() action: ", strerror(err));
err = posix_spawn_file_actions_addclose(&actions, child_pipe_[channel]);
err = posix_spawn_file_actions_addclose(&actions, child_fds_[channel]);
FUZZTEST_INTERNAL_CHECK(err == 0,
"Cannot add close() action: ", strerror(err));
}
Expand Down Expand Up @@ -193,10 +200,10 @@ void SubProcess::ReadChildOutput(std::string* stdout_output,
std::string* stderr_output) {
// Set up poll()-ing the pipes.
constexpr int fd_count = 2;
struct pollfd pfd[fd_count];
struct pollfd pfd[fd_count + 1];
std::string* out_str[fd_count];
for (int channel : {kStdOutIdx, kStdErrIdx}) {
pfd[channel].fd = parent_pipe_[channel];
pfd[channel].fd = parent_fds_[channel];
pfd[channel].events = POLLIN;
pfd[channel].revents = 0;
out_str[channel] = channel == kStdOutIdx ? stdout_output : stderr_output;
Expand Down Expand Up @@ -247,7 +254,7 @@ int Wait(pid_t pid) {
// TODO(lszekeres): Consider optimizing this further by eliminating polling.
// Could potentially be done using pselect() to wait for SIGCHLD with a timeout.
// I.e., by setting all args to null, except timeout with a sigmask for SIGCHLD.
int WaitWithTimeout(pid_t pid, absl::Duration timeout) {
int WaitWithTimeout(pid_t pid, int fds_to_shutdown[2], absl::Duration timeout) {
int status;
const absl::Time wait_until = absl::Now() + timeout;
constexpr absl::Duration sleep_duration = absl::Milliseconds(100);
Expand All @@ -259,17 +266,25 @@ int WaitWithTimeout(pid_t pid, absl::Duration timeout) {
if (absl::Now() > wait_until) {
FUZZTEST_INTERNAL_CHECK(kill(pid, SIGTERM) == 0,
"Cannot kill(): ", strerror(errno));
return Wait(pid);
status = Wait(pid);
break;
} else {
absl::SleepFor(sleep_duration);
continue;
}
} else if (ret == pid && (WIFEXITED(status) || WIFSIGNALED(status))) {
return status;
break;
} else {
FUZZTEST_INTERNAL_CHECK(false, "wait() error: ", strerror(errno));
}
}
FUZZTEST_INTERNAL_CHECK(
shutdown(fds_to_shutdown[0], SHUT_RD) == 0,
"Cannot shutdown fds_to_shutdown: ", fds_to_shutdown[0], strerror(errno));
FUZZTEST_INTERNAL_CHECK(
shutdown(fds_to_shutdown[1], SHUT_RD) == 0,
"Cannot shutdown fds_to_shutdown: ", fds_to_shutdown[1], strerror(errno));
return status;
}

} // anonymous namespace
Expand All @@ -278,15 +293,17 @@ RunResults SubProcess::Run(
const std::vector<std::string>& command_line,
const absl::flat_hash_map<std::string, std::string>& environment,
absl::Duration timeout) {
CreatePipes();
CreateCommunicationFds();
pid_t child_pid = StartChild(command_line, environment);
CloseChildPipes();
std::future<int> status =
std::async(std::launch::async, &WaitWithTimeout, child_pid, timeout);
CloseChildFds();
std::future<int> status = std::async(std::launch::async, &WaitWithTimeout,
child_pid, parent_fds_, timeout);
std::string stdout_output, stderr_output;
ReadChildOutput(&stdout_output, &stderr_output);
CloseParentPipes();
return {TerminationStatus(status.get()), stdout_output, stderr_output};
RunResults result = {TerminationStatus(status.get()), stdout_output,
stderr_output};
CloseParentFds();
return result;
}

#endif // !defined(_MSC_VER) && !(defined(__ANDROID_MIN_SDK_VERSION__) &&
Expand Down
10 changes: 10 additions & 0 deletions fuzztest/internal/subprocess_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/strings/str_cat.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"

namespace fuzztest::internal {
Expand Down Expand Up @@ -79,5 +80,14 @@ TEST(SubProcessTest, TimeoutIsEnforced) {
EXPECT_EQ(std_err.size(), 0);
}

TEST(SubProcessTest, ReturnsAfterChildProcessEnds) {
const auto before_time = absl::Now();
auto [status, std_out, std_err] = RunCommand({"bash", "-c", "sleep 4&"});
const auto after_time = absl::Now();
EXPECT_TRUE(status.Exited());
EXPECT_EQ(status, ExitCode(0));
EXPECT_LT(after_time - before_time, absl::Seconds(2));
}

} // namespace
} // namespace fuzztest::internal