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Merge pull request #8314 from poettering/rearrange-stdio

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refactor how we rearrange fds for stdin/stdout/stderr
This commit is contained in:
Lennart Poettering 2018-03-02 15:42:03 +01:00 committed by GitHub
commit 6cc7e918ff
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GPG Key ID: 4AEE18F83AFDEB23
18 changed files with 236 additions and 216 deletions
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3
TODO
View File

@ -24,6 +24,9 @@ Janitorial Clean-ups:
Features:
* add proper dbus APIs for the various sd_notify() commands, such as MAINPID=1
and so on, which would mean we could report errors and such.
* block setrlimit(RLIMIT_NOPROC) (and other per-user limits) in nspawn when userns is not on
* nss-systemd: implement enumeration, that shows all dynamic users plus the

9
src/activate/activate.c
View File

@ -199,15 +199,10 @@ static int exec_process(const char* name, char **argv, char **env, int start_fd,
if (arg_inetd) {
assert(n_fds == 1);
r = dup2(start_fd, STDIN_FILENO);
r = rearrange_stdio(start_fd, start_fd, STDERR_FILENO); /* invalidates start_fd on success + error */
if (r < 0)
return log_error_errno(errno, "Failed to dup connection to stdin: %m");
return log_error_errno(errno, "Failed to move fd to stdin+stdout: %m");
r = dup2(start_fd, STDOUT_FILENO);
if (r < 0)
return log_error_errno(errno, "Failed to dup connection to stdout: %m");
start_fd = safe_close(start_fd);
} else {
if (start_fd != SD_LISTEN_FDS_START) {
assert(n_fds == 1);

7
src/basic/exec-util.c
View File

@ -62,12 +62,9 @@ static int do_spawn(const char *path, char *argv[], int stdout_fd, pid_t *pid) {
char *_argv[2];
if (stdout_fd >= 0) {
/* If the fd happens to be in the right place, go along with that */
if (stdout_fd != STDOUT_FILENO &&
dup2(stdout_fd, STDOUT_FILENO) < 0)
r = rearrange_stdio(STDIN_FILENO, stdout_fd, STDERR_FILENO);
if (r < 0)
_exit(EXIT_FAILURE);
(void) fd_cloexec(STDOUT_FILENO, false);
}
if (!argv) {

121
src/basic/fd-util.c
View File

@ -191,12 +191,6 @@ int fd_cloexec(int fd, bool cloexec) {
return 0;
}
void stdio_unset_cloexec(void) {
(void) fd_cloexec(STDIN_FILENO, false);
(void) fd_cloexec(STDOUT_FILENO, false);
(void) fd_cloexec(STDERR_FILENO, false);
}
_pure_ static bool fd_in_set(int fd, const int fdset[], unsigned n_fdset) {
unsigned i;
@ -615,3 +609,118 @@ int fd_move_above_stdio(int fd) {
(void) close(fd);
return copy;
}
int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd) {
int fd[3] = { /* Put together an array of fds we work on */
original_input_fd,
original_output_fd,
original_error_fd
};
int r, i,
null_fd = -1, /* if we open /dev/null, we store the fd to it here */
copy_fd[3] = { -1, -1, -1 }; /* This contains all fds we duplicate here temporarily, and hence need to close at the end */
bool null_readable, null_writable;
/* Sets up stdin, stdout, stderr with the three file descriptors passed in. If any of the descriptors is
* specified as -1 it will be connected with /dev/null instead. If any of the file descriptors is passed as
* itself (e.g. stdin as STDIN_FILENO) it is left unmodified, but the O_CLOEXEC bit is turned off should it be
* on.
*
* Note that if any of the passed file descriptors are > 2 they will be closed — both on success and on
* failure! Thus, callers should assume that when this function returns the input fds are invalidated.
*
* Note that when this function fails stdin/stdout/stderr might remain half set up!
*
* O_CLOEXEC is turned off for all three file descriptors (which is how it should be for
* stdin/stdout/stderr). */
null_readable = original_input_fd < 0;
null_writable = original_output_fd < 0 || original_error_fd < 0;
/* First step, open /dev/null once, if we need it */
if (null_readable || null_writable) {
/* Let's open this with O_CLOEXEC first, and convert it to non-O_CLOEXEC when we move the fd to the final position. */
null_fd = open("/dev/null", (null_readable && null_writable ? O_RDWR :
null_readable ? O_RDONLY : O_WRONLY) | O_CLOEXEC);
if (null_fd < 0) {
r = -errno;
goto finish;
}
/* If this fd is in the 0…2 range, let's move it out of it */
if (null_fd < 3) {
int copy;
copy = fcntl(null_fd, F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
if (copy < 0) {
r = -errno;
goto finish;
}
safe_close(null_fd);
null_fd = copy;
}
}
/* Let's assemble fd[] with the fds to install in place of stdin/stdout/stderr */
for (i = 0; i < 3; i++) {
if (fd[i] < 0)
fd[i] = null_fd; /* A negative parameter means: connect this one to /dev/null */
else if (fd[i] != i && fd[i] < 3) {
/* This fd is in the 0…2 territory, but not at its intended place, move it out of there, so that we can work there. */
copy_fd[i] = fcntl(fd[i], F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
if (copy_fd[i] < 0) {
r = -errno;
goto finish;
}
fd[i] = copy_fd[i];
}
}
/* At this point we now have the fds to use in fd[], and they are all above the stdio range, so that we
* have freedom to move them around. If the fds already were at the right places then the specific fds are
* -1. Let's now move them to the right places. This is the point of no return. */
for (i = 0; i < 3; i++) {
if (fd[i] == i) {
/* fd is already in place, but let's make sure O_CLOEXEC is off */
r = fd_cloexec(i, false);
if (r < 0)
goto finish;
} else {
assert(fd[i] > 2);
if (dup2(fd[i], i) < 0) { /* Turns off O_CLOEXEC on the new fd. */
r = -errno;
goto finish;
}
}
}
r = 0;
finish:
/* Close the original fds, but only if they were outside of the stdio range. Also, properly check for the same
* fd passed in multiple times. */
safe_close_above_stdio(original_input_fd);
if (original_output_fd != original_input_fd)
safe_close_above_stdio(original_output_fd);
if (original_error_fd != original_input_fd && original_error_fd != original_output_fd)
safe_close_above_stdio(original_error_fd);
/* Close the copies we moved > 2 */
for (i = 0; i < 3; i++)
safe_close(copy_fd[i]);
/* Close our null fd, if it's > 2 */
safe_close_above_stdio(null_fd);
return r;
}

7
src/basic/fd-util.h
View File

@ -71,7 +71,6 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(DIR*, closedir);
int fd_nonblock(int fd, bool nonblock);
int fd_cloexec(int fd, bool cloexec);
void stdio_unset_cloexec(void);
int close_all_fds(const int except[], unsigned n_except);
@ -100,3 +99,9 @@ int acquire_data_fd(const void *data, size_t size, unsigned flags);
IN_SET(r, ENOTCONN, ECONNRESET, ECONNREFUSED, ECONNABORTED, EPIPE, ENETUNREACH)
int fd_move_above_stdio(int fd);
int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd);
static inline int make_null_stdio(void) {
return rearrange_stdio(-1, -1, -1);
}

38
src/basic/terminal-util.c
View File

@ -628,9 +628,9 @@ int make_console_stdio(void) {
if (r < 0)
log_warning_errno(r, "Failed to reset terminal, ignoring: %m");
r = make_stdio(fd);
r = rearrange_stdio(fd, fd, fd); /* This invalidates 'fd' both on success and on failure. */
if (r < 0)
return log_error_errno(r, "Failed to duplicate terminal fd: %m");
return log_error_errno(r, "Failed to make terminal stdin/stdout/stderr: %m");
reset_terminal_feature_caches();
@ -905,40 +905,6 @@ bool on_tty(void) {
return cached_on_tty;
}
int make_stdio(int fd) {
int r = 0;
assert(fd >= 0);
if (dup2(fd, STDIN_FILENO) < 0)
r = -errno;
if (dup2(fd, STDOUT_FILENO) < 0 && r >= 0)
r = -errno;
if (dup2(fd, STDERR_FILENO) < 0 && r >= 0)
r = -errno;
safe_close_above_stdio(fd);
/* Explicitly unset O_CLOEXEC, since if fd was < 3, then dup2() was a NOP and the bit hence possibly set. */
stdio_unset_cloexec();
return r;
}
int make_null_stdio(void) {
int null_fd, r;
null_fd = open("/dev/null", O_RDWR|O_NOCTTY|O_CLOEXEC);
if (null_fd < 0)
return -errno;
r = make_stdio(null_fd);
reset_terminal_feature_caches();
return r;
}
int getttyname_malloc(int fd, char **ret) {
size_t l = 100;
int r;

2
src/basic/terminal-util.h
View File

@ -114,8 +114,6 @@ bool tty_is_console(const char *tty) _pure_;
int vtnr_from_tty(const char *tty);
const char *default_term_for_tty(const char *tty);
int make_stdio(int fd);
int make_null_stdio(void);
int make_console_stdio(void);
int fd_columns(int fd);

11
src/core/execute.c
View File

@ -765,15 +765,10 @@ static int setup_confirm_stdio(const char *vc, int *_saved_stdin, int *_saved_st
if (r < 0)
return r;
if (dup2(fd, STDIN_FILENO) < 0)
return -errno;
if (dup2(fd, STDOUT_FILENO) < 0)
return -errno;
if (fd >= 2)
safe_close(fd);
r = rearrange_stdio(fd, fd, STDERR_FILENO);
fd = -1;
if (r < 0)
return r;
*_saved_stdin = saved_stdin;
*_saved_stdout = saved_stdout;

38
src/import/import-common.c
View File

@ -87,7 +87,6 @@ int import_fork_tar_x(const char *path, pid_t *ret) {
if (r < 0)
return r;
if (r == 0) {
int null_fd;
uint64_t retain =
(1ULL << CAP_CHOWN) |
(1ULL << CAP_FOWNER) |
@ -100,26 +99,12 @@ int import_fork_tar_x(const char *path, pid_t *ret) {
pipefd[1] = safe_close(pipefd[1]);
r = move_fd(pipefd[0], STDIN_FILENO, false);
r = rearrange_stdio(pipefd[0], -1, STDERR_FILENO);
if (r < 0) {
log_error_errno(r, "Failed to move fd: %m");
log_error_errno(r, "Failed to rearrange stdin/stdout: %m");
_exit(EXIT_FAILURE);
}
null_fd = open("/dev/null", O_WRONLY|O_NOCTTY);
if (null_fd < 0) {
log_error_errno(errno, "Failed to open /dev/null: %m");
_exit(EXIT_FAILURE);
}
r = move_fd(null_fd, STDOUT_FILENO, false);
if (r < 0) {
log_error_errno(r, "Failed to move fd: %m");
_exit(EXIT_FAILURE);
}
stdio_unset_cloexec();
if (unshare(CLONE_NEWNET) < 0)
log_error_errno(errno, "Failed to lock tar into network namespace, ignoring: %m");
@ -156,33 +141,18 @@ int import_fork_tar_c(const char *path, pid_t *ret) {
if (r < 0)
return r;
if (r == 0) {
int null_fd;
uint64_t retain = (1ULL << CAP_DAC_OVERRIDE);
/* Child */
pipefd[0] = safe_close(pipefd[0]);
r = move_fd(pipefd[1], STDOUT_FILENO, false);
r = rearrange_stdio(-1, pipefd[1], STDERR_FILENO);
if (r < 0) {
log_error_errno(r, "Failed to move fd: %m");
log_error_errno(r, "Failed to rearrange stdin/stdout: %m");
_exit(EXIT_FAILURE);
}
null_fd = open("/dev/null", O_RDONLY|O_NOCTTY);
if (null_fd < 0) {
log_error_errno(errno, "Failed to open /dev/null: %m");
_exit(EXIT_FAILURE);
}
r = move_fd(null_fd, STDIN_FILENO, false);
if (r < 0) {
log_error_errno(errno, "Failed to move fd: %m");
_exit(EXIT_FAILURE);
}
stdio_unset_cloexec();
if (unshare(CLONE_NEWNET) < 0)
log_error_errno(errno, "Failed to lock tar into network namespace, ignoring: %m");

53
src/import/importd.c
View File

@ -395,57 +395,14 @@ static int transfer_start(Transfer *t) {
pipefd[0] = safe_close(pipefd[0]);
if (dup2(pipefd[1], STDERR_FILENO) != STDERR_FILENO) {
log_error_errno(errno, "Failed to dup2() fd: %m");
r = rearrange_stdio(t->stdin_fd,
t->stdout_fd < 0 ? pipefd[1] : t->stdout_fd,
pipefd[1]);
if (r < 0) {
log_error_errno(r, "Failed to set stdin/stdout/stderr: %m");
_exit(EXIT_FAILURE);
}
if (t->stdout_fd >= 0) {
if (dup2(t->stdout_fd, STDOUT_FILENO) != STDOUT_FILENO) {
log_error_errno(errno, "Failed to dup2() fd: %m");
_exit(EXIT_FAILURE);
}
if (t->stdout_fd != STDOUT_FILENO)
safe_close(t->stdout_fd);
} else {
if (dup2(pipefd[1], STDOUT_FILENO) != STDOUT_FILENO) {
log_error_errno(errno, "Failed to dup2() fd: %m");
_exit(EXIT_FAILURE);
}
}
if (!IN_SET(pipefd[1], STDOUT_FILENO, STDERR_FILENO))
pipefd[1] = safe_close(pipefd[1]);
if (t->stdin_fd >= 0) {
if (dup2(t->stdin_fd, STDIN_FILENO) != STDIN_FILENO) {
log_error_errno(errno, "Failed to dup2() fd: %m");
_exit(EXIT_FAILURE);
}
if (t->stdin_fd != STDIN_FILENO)
safe_close(t->stdin_fd);
} else {
int null_fd;
null_fd = open("/dev/null", O_RDONLY|O_NOCTTY);
if (null_fd < 0) {
log_error_errno(errno, "Failed to open /dev/null: %m");
_exit(EXIT_FAILURE);
}
if (dup2(null_fd, STDIN_FILENO) != STDIN_FILENO) {
log_error_errno(errno, "Failed to dup2() fd: %m");
_exit(EXIT_FAILURE);
}
if (null_fd != STDIN_FILENO)
safe_close(null_fd);
}
stdio_unset_cloexec();
if (setenv("SYSTEMD_LOG_TARGET", "console-prefixed", 1) < 0 ||
setenv("NOTIFY_SOCKET", "/run/systemd/import/notify", 1) < 0) {
log_error_errno(errno, "setenv() failed: %m");

19
src/import/pull-common.c
View File

@ -483,27 +483,14 @@ int pull_verify(PullJob *main_job,
NULL /* trailing NULL */
};
unsigned k = ELEMENTSOF(cmd) - 6;
int null_fd;
/* Child */
gpg_pipe[1] = safe_close(gpg_pipe[1]);
r = move_fd(gpg_pipe[0], STDIN_FILENO, false);
r = rearrange_stdio(gpg_pipe[0], -1, STDERR_FILENO);
if (r < 0) {
log_error_errno(errno, "Failed to move fd: %m");
_exit(EXIT_FAILURE);
}
null_fd = open("/dev/null", O_WRONLY|O_NOCTTY);
if (null_fd < 0) {
log_error_errno(errno, "Failed to open /dev/null: %m");
_exit(EXIT_FAILURE);
}
r = move_fd(null_fd, STDOUT_FILENO, false);
if (r < 0) {
log_error_errno(errno, "Failed to move fd: %m");
log_error_errno(r, "Failed to rearrange stdin/stdout: %m");
_exit(EXIT_FAILURE);
}
@ -524,8 +511,6 @@ int pull_verify(PullJob *main_job,
cmd[k++] = NULL;
}
stdio_unset_cloexec();
execvp("gpg2", (char * const *) cmd);
execvp("gpg", (char * const *) cmd);
log_error_errno(errno, "Failed to execute gpg: %m");

11
src/journal-remote/journal-remote.c
View File

@ -96,23 +96,20 @@ static int spawn_child(const char* child, char** argv) {
/* In the child */
if (r == 0) {
safe_close(fd[0]);
r = dup2(fd[1], STDOUT_FILENO);
r = rearrange_stdio(STDIN_FILENO, fd[1], STDERR_FILENO);
if (r < 0) {
log_error_errno(errno, "Failed to dup pipe to stdout: %m");
log_error_errno(r, "Failed to dup pipe to stdout: %m");
_exit(EXIT_FAILURE);
}
safe_close_pair(fd);
execvp(child, argv);
log_error_errno(errno, "Failed to exec child %s: %m", child);
_exit(EXIT_FAILURE);
}
r = close(fd[1]);
if (r < 0)
log_warning_errno(errno, "Failed to close write end of pipe: %m");
safe_close(fd[1]);
r = fd_nonblock(fd[0], true);
if (r < 0)

9
src/journal/cat.c
View File

@ -135,14 +135,13 @@ int main(int argc, char *argv[]) {
saved_stderr = fcntl(STDERR_FILENO, F_DUPFD_CLOEXEC, 3);
if (dup3(fd, STDOUT_FILENO, 0) < 0 ||
dup3(fd, STDERR_FILENO, 0) < 0) {
r = log_error_errno(errno, "Failed to duplicate fd: %m");
r = rearrange_stdio(STDIN_FILENO, fd, fd); /* Invalidates fd on succcess + error! */
fd = -1;
if (r < 0) {
log_error_errno(r, "Failed to rearrange stdout/stderr: %m");
goto finish;
}
fd = safe_close_above_stdio(fd);
if (argc <= optind)
(void) execl("/bin/cat", "/bin/cat", NULL);
else

4
src/libsystemd/sd-bus/bus-message.c
View File

@ -2646,7 +2646,7 @@ _public_ int sd_bus_message_append_array_memfd(
if (r < 0)
return r;
copy_fd = dup(memfd);
copy_fd = fcntl(memfd, F_DUPFD_CLOEXEC, 3);
if (copy_fd < 0)
return copy_fd;
@ -2721,7 +2721,7 @@ _public_ int sd_bus_message_append_string_memfd(
if (r < 0)
return r;
copy_fd = dup(memfd);
copy_fd = fcntl(memfd, FD_CLOEXEC, 3);
if (copy_fd < 0)
return copy_fd;

9
src/libsystemd/sd-bus/bus-socket.c
View File

@ -960,14 +960,11 @@ int bus_socket_exec(sd_bus *b) {
if (r == 0) {
/* Child */
assert_se(dup3(s[1], STDIN_FILENO, 0) == STDIN_FILENO);
assert_se(dup3(s[1], STDOUT_FILENO, 0) == STDOUT_FILENO);
safe_close(s[0]);
if (!IN_SET(s[1], STDIN_FILENO, STDOUT_FILENO))
safe_close(s[1]);
if (rearrange_stdio(s[1], s[1], STDERR_FILENO) < 0)
_exit(EXIT_FAILURE);
(void) fd_cloexec(STDIN_FILENO, false);
(void) fd_cloexec(STDOUT_FILENO, false);
(void) fd_nonblock(STDIN_FILENO, false);
(void) fd_nonblock(STDOUT_FILENO, false);

20
src/nspawn/nspawn-setuid.c
View File

@ -54,26 +54,12 @@ static int spawn_getent(const char *database, const char *key, pid_t *rpid) {
}
if (r == 0) {
char *empty_env = NULL;
int nullfd;
if (dup3(pipe_fds[1], STDOUT_FILENO, 0) < 0)
safe_close(pipe_fds[0]);
if (rearrange_stdio(-1, pipe_fds[1], -1) < 0)
_exit(EXIT_FAILURE);
safe_close_above_stdio(pipe_fds[0]);
safe_close_above_stdio(pipe_fds[1]);
nullfd = open("/dev/null", O_RDWR);
if (nullfd < 0)
_exit(EXIT_FAILURE);
if (dup3(nullfd, STDIN_FILENO, 0) < 0)
_exit(EXIT_FAILURE);
if (dup3(nullfd, STDERR_FILENO, 0) < 0)
_exit(EXIT_FAILURE);
safe_close_above_stdio(nullfd);
close_all_fds(NULL, 0);
execle("/usr/bin/getent", "getent", database, key, NULL, &empty_env);

22
src/nspawn/nspawn.c
View File

@ -2582,23 +2582,15 @@ static int outer_child(
return log_error_errno(errno, "PR_SET_PDEATHSIG failed: %m");
if (interactive) {
close_nointr(STDIN_FILENO);
close_nointr(STDOUT_FILENO);
close_nointr(STDERR_FILENO);
int terminal;
r = open_terminal(console, O_RDWR);
if (r != STDIN_FILENO) {
if (r >= 0) {
safe_close(r);
r = -EINVAL;
}
terminal = open_terminal(console, O_RDWR);
if (terminal < 0)
return log_error_errno(terminal, "Failed to open console: %m");
return log_error_errno(r, "Failed to open console: %m");
}
if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO ||
dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO)
return log_error_errno(errno, "Failed to duplicate console: %m");
r = rearrange_stdio(terminal, terminal, terminal); /* invalidates 'terminal' on success and failure */
if (r < 0)
return log_error_errno(r, "Failed to move console to stdin/stdout/stderr: %m");
}
r = reset_audit_loginuid();

69
src/test/test-fd-util.c
View File

@ -25,6 +25,8 @@
#include "fd-util.h"
#include "fileio.h"
#include "macro.h"
#include "path-util.h"
#include "process-util.h"
#include "random-util.h"
#include "string-util.h"
#include "util.h"
@ -173,6 +175,72 @@ static void test_fd_move_above_stdio(void) {
assert_se(close_nointr(new_fd) != EBADF);
}
static void test_rearrange_stdio(void) {
pid_t pid;
int r;
r = safe_fork("rearrange", FORK_WAIT|FORK_LOG, &pid);
assert_se(r >= 0);
if (r == 0) {
_cleanup_free_ char *path = NULL;
char buffer[10];
/* Child */
safe_close(STDERR_FILENO); /* Let's close an fd < 2, to make it more interesting */
assert_se(rearrange_stdio(-1, -1, -1) >= 0);
assert_se(fd_get_path(STDIN_FILENO, &path) >= 0);
assert_se(path_equal(path, "/dev/null"));
path = mfree(path);
assert_se(fd_get_path(STDOUT_FILENO, &path) >= 0);
assert_se(path_equal(path, "/dev/null"));
path = mfree(path);
assert_se(fd_get_path(STDOUT_FILENO, &path) >= 0);
assert_se(path_equal(path, "/dev/null"));
path = mfree(path);
safe_close(STDIN_FILENO);
safe_close(STDOUT_FILENO);
safe_close(STDERR_FILENO);
{
int pair[2];
assert_se(pipe(pair) >= 0);
assert_se(pair[0] == 0);
assert_se(pair[1] == 1);
assert_se(fd_move_above_stdio(0) == 3);
}
assert_se(open("/dev/full", O_WRONLY|O_CLOEXEC) == 0);
assert_se(acquire_data_fd("foobar", 6, 0) == 2);
assert_se(rearrange_stdio(2, 0, 1) >= 0);
assert_se(write(1, "x", 1) < 0 && errno == ENOSPC);
assert_se(write(2, "z", 1) == 1);
assert_se(read(3, buffer, sizeof(buffer)) == 1);
assert_se(buffer[0] == 'z');
assert_se(read(0, buffer, sizeof(buffer)) == 6);
assert_se(memcmp(buffer, "foobar", 6) == 0);
assert_se(rearrange_stdio(-1, 1, 2) >= 0);
assert_se(write(1, "a", 1) < 0 && errno == ENOSPC);
assert_se(write(2, "y", 1) == 1);
assert_se(read(3, buffer, sizeof(buffer)) == 1);
assert_se(buffer[0] == 'y');
assert_se(fd_get_path(0, &path) >= 0);
assert_se(path_equal(path, "/dev/null"));
path = mfree(path);
_exit(EXIT_SUCCESS);
}
}
int main(int argc, char *argv[]) {
test_close_many();
test_close_nointr();
@ -180,6 +248,7 @@ int main(int argc, char *argv[]) {
test_open_serialization_fd();
test_acquire_data_fd();
test_fd_move_above_stdio();
test_rearrange_stdio();
return 0;
}