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Copy path_posixsubprocess.c
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1359 lines (1217 loc) · 44.7 KB
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/* Authors: Gregory P. Smith & Jeffrey Yasskin */
#ifndef Py_BUILD_CORE_BUILTIN
# define Py_BUILD_CORE_MODULE 1
#endif
#include "Python.h"
#include "pycore_fileutils.h" // _Py_set_inheritable_async_safe()
#include "pycore_interp.h" // _PyInterpreterState_GetFinalizing()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_signal.h" // _Py_RestoreSignals()
#if defined(HAVE_PIPE2) && !defined(_GNU_SOURCE)
# define _GNU_SOURCE
#endif
#include <unistd.h> // close()
#include <fcntl.h> // fcntl()
#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#if defined(HAVE_SYS_STAT_H)
# include <sys/stat.h> // stat()
#endif
#ifdef HAVE_SYS_SYSCALL_H
# include <sys/syscall.h>
#endif
#if defined(HAVE_SYS_RESOURCE_H)
# include <sys/resource.h>
#endif
#ifdef HAVE_DIRENT_H
# include <dirent.h> // opendir()
#endif
#if defined(HAVE_SETGROUPS)
# include <grp.h> // setgroups()
#endif
#include "posixmodule.h"
#ifdef _Py_MEMORY_SANITIZER
# include <sanitizer/msan_interface.h>
#endif
#if defined(__ANDROID__) && __ANDROID_API__ < 21 && !defined(SYS_getdents64)
# include <sys/linux-syscalls.h>
# define SYS_getdents64 __NR_getdents64
#endif
#if defined(__linux__) && defined(HAVE_VFORK) && defined(HAVE_SIGNAL_H) && \
defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
/* If this is ever expanded to non-Linux platforms, verify what calls are
* allowed after vfork(). Ex: setsid() may be disallowed on macOS? */
# include <signal.h>
# define VFORK_USABLE 1
#endif
#if defined(__sun) && defined(__SVR4)
/* readdir64 is used to work around Solaris 9 bug 6395699. */
# define readdir readdir64
# define dirent dirent64
# if !defined(HAVE_DIRFD)
/* Some versions of Solaris lack dirfd(). */
# define dirfd(dirp) ((dirp)->dd_fd)
# define HAVE_DIRFD
# endif
#endif
#if defined(__FreeBSD__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__DragonFly__)
# define FD_DIR "/dev/fd"
#else
# define FD_DIR "/proc/self/fd"
#endif
#ifdef NGROUPS_MAX
#define MAX_GROUPS NGROUPS_MAX
#else
#define MAX_GROUPS 64
#endif
#define POSIX_CALL(call) do { if ((call) == -1) goto error; } while (0)
static struct PyModuleDef _posixsubprocessmodule;
/*[clinic input]
module _posixsubprocess
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=c62211df27cf7334]*/
/*[python input]
class pid_t_converter(CConverter):
type = 'pid_t'
format_unit = '" _Py_PARSE_PID "'
def parse_arg(self, argname, displayname, *, limited_capi):
return self.format_code("""
{paramname} = PyLong_AsPid({argname});
if ({paramname} == -1 && PyErr_Occurred()) {{{{
goto exit;
}}}}
""",
argname=argname)
[python start generated code]*/
/*[python end generated code: output=da39a3ee5e6b4b0d input=c94349aa1aad151d]*/
#include "clinic/_posixsubprocess.c.h"
/* Convert ASCII to a positive int, no libc call. no overflow. -1 on error. */
static int
_pos_int_from_ascii(const char *name)
{
int num = 0;
while (*name >= '0' && *name <= '9') {
num = num * 10 + (*name - '0');
++name;
}
if (*name)
return -1; /* Non digit found, not a number. */
return num;
}
#if defined(__FreeBSD__) || defined(__DragonFly__)
/* When /dev/fd isn't mounted it is often a static directory populated
* with 0 1 2 or entries for 0 .. 63 on FreeBSD, NetBSD, OpenBSD and DragonFlyBSD.
* NetBSD and OpenBSD have a /proc fs available (though not necessarily
* mounted) and do not have fdescfs for /dev/fd. MacOS X has a devfs
* that properly supports /dev/fd.
*/
static int
_is_fdescfs_mounted_on_dev_fd(void)
{
struct stat dev_stat;
struct stat dev_fd_stat;
if (stat("/dev", &dev_stat) != 0)
return 0;
if (stat(FD_DIR, &dev_fd_stat) != 0)
return 0;
if (dev_stat.st_dev == dev_fd_stat.st_dev)
return 0; /* / == /dev == /dev/fd means it is static. #fail */
return 1;
}
#endif
/* Returns 1 if there is a problem with fd_sequence, 0 otherwise. */
static int
_sanity_check_python_fd_sequence(PyObject *fd_sequence)
{
Py_ssize_t seq_idx;
long prev_fd = -1;
for (seq_idx = 0; seq_idx < PyTuple_GET_SIZE(fd_sequence); ++seq_idx) {
PyObject* py_fd = PyTuple_GET_ITEM(fd_sequence, seq_idx);
long iter_fd;
if (!PyLong_Check(py_fd)) {
return 1;
}
iter_fd = PyLong_AsLong(py_fd);
if (iter_fd < 0 || iter_fd <= prev_fd || iter_fd > INT_MAX) {
/* Negative, overflow, unsorted, too big for a fd. */
return 1;
}
prev_fd = iter_fd;
}
return 0;
}
/* Is fd found in the sorted Python Sequence? */
static int
_is_fd_in_sorted_fd_sequence(int fd, int *fd_sequence,
Py_ssize_t fd_sequence_len)
{
/* Binary search. */
Py_ssize_t search_min = 0;
Py_ssize_t search_max = fd_sequence_len - 1;
if (search_max < 0)
return 0;
do {
long middle = (search_min + search_max) / 2;
long middle_fd = fd_sequence[middle];
if (fd == middle_fd)
return 1;
if (fd > middle_fd)
search_min = middle + 1;
else
search_max = middle - 1;
} while (search_min <= search_max);
return 0;
}
// Forward declaration
static void _Py_FreeCharPArray(char *const array[]);
/*
* Flatten a sequence of bytes() objects into a C array of
* NULL terminated string pointers with a NULL char* terminating the array.
* (ie: an argv or env list)
*
* Memory allocated for the returned list is allocated using PyMem_Malloc()
* and MUST be freed by _Py_FreeCharPArray().
*/
static char *const *
_PySequence_BytesToCharpArray(PyObject* self)
{
char **array;
Py_ssize_t i, argc;
PyObject *item = NULL;
Py_ssize_t size;
argc = PySequence_Size(self);
if (argc == -1)
return NULL;
assert(argc >= 0);
if ((size_t)argc > (PY_SSIZE_T_MAX-sizeof(char *)) / sizeof(char *)) {
PyErr_NoMemory();
return NULL;
}
array = PyMem_Malloc((argc + 1) * sizeof(char *));
if (array == NULL) {
PyErr_NoMemory();
return NULL;
}
for (i = 0; i < argc; ++i) {
char *data;
item = PySequence_GetItem(self, i);
if (item == NULL) {
/* NULL terminate before freeing. */
array[i] = NULL;
goto fail;
}
/* check for embedded null bytes */
if (PyBytes_AsStringAndSize(item, &data, NULL) < 0) {
/* NULL terminate before freeing. */
array[i] = NULL;
goto fail;
}
size = PyBytes_GET_SIZE(item) + 1;
array[i] = PyMem_Malloc(size);
if (!array[i]) {
PyErr_NoMemory();
goto fail;
}
memcpy(array[i], data, size);
Py_DECREF(item);
}
array[argc] = NULL;
return array;
fail:
Py_XDECREF(item);
_Py_FreeCharPArray(array);
return NULL;
}
/* Free's a NULL terminated char** array of C strings. */
static void
_Py_FreeCharPArray(char *const array[])
{
Py_ssize_t i;
for (i = 0; array[i] != NULL; ++i) {
PyMem_Free(array[i]);
}
PyMem_Free((void*)array);
}
/*
* Do all the Python C API calls in the parent process to turn the pass_fds
* "py_fds_to_keep" tuple into a C array. The caller owns allocation and
* freeing of the array.
*
* On error an unknown number of array elements may have been filled in.
* A Python exception has been set when an error is returned.
*
* Returns: -1 on error, 0 on success.
*/
static int
convert_fds_to_keep_to_c(PyObject *py_fds_to_keep, int *c_fds_to_keep)
{
Py_ssize_t i, len;
len = PyTuple_GET_SIZE(py_fds_to_keep);
for (i = 0; i < len; ++i) {
PyObject* fdobj = PyTuple_GET_ITEM(py_fds_to_keep, i);
long fd = PyLong_AsLong(fdobj);
if (fd == -1 && PyErr_Occurred()) {
return -1;
}
if (fd < 0 || fd > INT_MAX) {
PyErr_SetString(PyExc_ValueError,
"fd out of range in fds_to_keep.");
return -1;
}
c_fds_to_keep[i] = (int)fd;
}
return 0;
}
/* This function must be async-signal-safe as it is called from child_exec()
* after fork() or vfork().
*/
static int
make_inheritable(int *c_fds_to_keep, Py_ssize_t len, int errpipe_write)
{
Py_ssize_t i;
for (i = 0; i < len; ++i) {
int fd = c_fds_to_keep[i];
if (fd == errpipe_write) {
/* errpipe_write is part of fds_to_keep. It must be closed at
exec(), but kept open in the child process until exec() is
called. */
continue;
}
if (_Py_set_inheritable_async_safe(fd, 1, NULL) < 0)
return -1;
}
return 0;
}
/* Get the maximum file descriptor that could be opened by this process.
* This function is async signal safe for use between fork() and exec().
*/
static long
safe_get_max_fd(void)
{
long local_max_fd;
#if defined(__NetBSD__)
local_max_fd = fcntl(0, F_MAXFD);
if (local_max_fd >= 0)
return local_max_fd;
#endif
#if defined(HAVE_SYS_RESOURCE_H) && defined(__OpenBSD__)
struct rlimit rl;
/* Not on the POSIX async signal safe functions list but likely
* safe. TODO - Someone should audit OpenBSD to make sure. */
if (getrlimit(RLIMIT_NOFILE, &rl) >= 0)
return (long) rl.rlim_max;
#endif
#ifdef _SC_OPEN_MAX
local_max_fd = sysconf(_SC_OPEN_MAX);
if (local_max_fd == -1)
#endif
local_max_fd = 256; /* Matches legacy Lib/subprocess.py behavior. */
return local_max_fd;
}
/* Close all file descriptors in the given range except for those in
* fds_to_keep by invoking closer on each subrange.
*
* If end_fd == -1, it's guessed via safe_get_max_fd(), but it isn't
* possible to know for sure what the max fd to go up to is for
* processes with the capability of raising their maximum, or in case
* a process opened a high fd and then lowered its maximum.
*/
static int
_close_range_except(int start_fd,
int end_fd,
int *fds_to_keep,
Py_ssize_t fds_to_keep_len,
int (*closer)(int, int))
{
if (end_fd == -1) {
end_fd = Py_MIN(safe_get_max_fd(), INT_MAX);
}
Py_ssize_t keep_seq_idx;
/* As fds_to_keep is sorted we can loop through the list closing
* fds in between any in the keep list falling within our range. */
for (keep_seq_idx = 0; keep_seq_idx < fds_to_keep_len; ++keep_seq_idx) {
int keep_fd = fds_to_keep[keep_seq_idx];
if (keep_fd < start_fd)
continue;
if (closer(start_fd, keep_fd - 1) != 0)
return -1;
start_fd = keep_fd + 1;
}
if (start_fd <= end_fd) {
if (closer(start_fd, end_fd) != 0)
return -1;
}
return 0;
}
#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
/* It doesn't matter if d_name has room for NAME_MAX chars; we're using this
* only to read a directory of short file descriptor number names. The kernel
* will return an error if we didn't give it enough space. Highly Unlikely.
* This structure is very old and stable: It will not change unless the kernel
* chooses to break compatibility with all existing binaries. Highly Unlikely.
*/
struct linux_dirent64 {
unsigned long long d_ino;
long long d_off;
unsigned short d_reclen; /* Length of this linux_dirent */
unsigned char d_type;
char d_name[256]; /* Filename (null-terminated) */
};
static int
_brute_force_closer(int first, int last)
{
for (int i = first; i <= last; i++) {
/* Ignore errors */
(void)close(i);
}
return 0;
}
/* Close all open file descriptors in the range from start_fd and higher
* Do not close any in the sorted fds_to_keep list.
*
* This version is async signal safe as it does not make any unsafe C library
* calls, malloc calls or handle any locks. It is _unfortunate_ to be forced
* to resort to making a kernel system call directly but this is the ONLY api
* available that does no harm. opendir/readdir/closedir perform memory
* allocation and locking so while they usually work they are not guaranteed
* to (especially if you have replaced your malloc implementation). A version
* of this function that uses those can be found in the _maybe_unsafe variant.
*
* This is Linux specific because that is all I am ready to test it on. It
* should be easy to add OS specific dirent or dirent64 structures and modify
* it with some cpp #define magic to work on other OSes as well if you want.
*/
static void
_close_open_fds_safe(int start_fd, int *fds_to_keep, Py_ssize_t fds_to_keep_len)
{
int fd_dir_fd;
fd_dir_fd = _Py_open_noraise(FD_DIR, O_RDONLY);
if (fd_dir_fd == -1) {
/* No way to get a list of open fds. */
_close_range_except(start_fd, -1,
fds_to_keep, fds_to_keep_len,
_brute_force_closer);
return;
} else {
char buffer[sizeof(struct linux_dirent64)];
int bytes;
while ((bytes = syscall(SYS_getdents64, fd_dir_fd,
(struct linux_dirent64 *)buffer,
sizeof(buffer))) > 0) {
struct linux_dirent64 *entry;
int offset;
#ifdef _Py_MEMORY_SANITIZER
__msan_unpoison(buffer, bytes);
#endif
for (offset = 0; offset < bytes; offset += entry->d_reclen) {
int fd;
entry = (struct linux_dirent64 *)(buffer + offset);
if ((fd = _pos_int_from_ascii(entry->d_name)) < 0)
continue; /* Not a number. */
if (fd != fd_dir_fd && fd >= start_fd &&
!_is_fd_in_sorted_fd_sequence(fd, fds_to_keep,
fds_to_keep_len)) {
close(fd);
}
}
}
close(fd_dir_fd);
}
}
#define _close_open_fds_fallback _close_open_fds_safe
#else /* NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
static int
_unsafe_closer(int first, int last)
{
_Py_closerange(first, last);
return 0;
}
/* Close all open file descriptors from start_fd and higher.
* Do not close any in the sorted fds_to_keep tuple.
*
* This function violates the strict use of async signal safe functions. :(
* It calls opendir(), readdir() and closedir(). Of these, the one most
* likely to ever cause a problem is opendir() as it performs an internal
* malloc(). Practically this should not be a problem. The Java VM makes the
* same calls between fork and exec in its own UNIXProcess_md.c implementation.
*
* readdir_r() is not used because it provides no benefit. It is typically
* implemented as readdir() followed by memcpy(). See also:
* http://womble.decadent.org.uk/readdir_r-advisory.html
*/
static void
_close_open_fds_maybe_unsafe(int start_fd, int *fds_to_keep,
Py_ssize_t fds_to_keep_len)
{
DIR *proc_fd_dir;
#ifndef HAVE_DIRFD
while (_is_fd_in_sorted_fd_sequence(start_fd, fds_to_keep,
fds_to_keep_len)) {
++start_fd;
}
/* Close our lowest fd before we call opendir so that it is likely to
* reuse that fd otherwise we might close opendir's file descriptor in
* our loop. This trick assumes that fd's are allocated on a lowest
* available basis. */
close(start_fd);
++start_fd;
#endif
#if defined(__FreeBSD__) || defined(__DragonFly__)
if (!_is_fdescfs_mounted_on_dev_fd())
proc_fd_dir = NULL;
else
#endif
#if defined(_AIX)
char fd_path[PATH_MAX];
snprintf(fd_path, sizeof(fd_path), "/proc/%ld/fd", (long)getpid());
proc_fd_dir = opendir(fd_path);
#else
proc_fd_dir = opendir(FD_DIR);
#endif
if (!proc_fd_dir) {
/* No way to get a list of open fds. */
_close_range_except(start_fd, -1, fds_to_keep, fds_to_keep_len,
_unsafe_closer);
} else {
struct dirent *dir_entry;
#ifdef HAVE_DIRFD
int fd_used_by_opendir = dirfd(proc_fd_dir);
#else
int fd_used_by_opendir = start_fd - 1;
#endif
errno = 0;
while ((dir_entry = readdir(proc_fd_dir))) {
int fd;
if ((fd = _pos_int_from_ascii(dir_entry->d_name)) < 0)
continue; /* Not a number. */
if (fd != fd_used_by_opendir && fd >= start_fd &&
!_is_fd_in_sorted_fd_sequence(fd, fds_to_keep,
fds_to_keep_len)) {
close(fd);
}
errno = 0;
}
if (errno) {
/* readdir error, revert behavior. Highly Unlikely. */
_close_range_except(start_fd, -1, fds_to_keep, fds_to_keep_len,
_unsafe_closer);
}
closedir(proc_fd_dir);
}
}
#define _close_open_fds_fallback _close_open_fds_maybe_unsafe
#endif /* else NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
/* We can use close_range() library function only if it's known to be
* async-signal-safe.
*
* On Linux, glibc explicitly documents it to be a thin wrapper over
* the system call, and other C libraries are likely to follow glibc.
*/
#if defined(HAVE_CLOSE_RANGE) && \
(defined(__linux__) || defined(__FreeBSD__))
#define HAVE_ASYNC_SAFE_CLOSE_RANGE
static int
_close_range_closer(int first, int last)
{
return close_range(first, last, 0);
}
#endif
static void
_close_open_fds(int start_fd, int *fds_to_keep, Py_ssize_t fds_to_keep_len)
{
#ifdef HAVE_ASYNC_SAFE_CLOSE_RANGE
if (_close_range_except(
start_fd, INT_MAX, fds_to_keep, fds_to_keep_len,
_close_range_closer) == 0) {
return;
}
#endif
_close_open_fds_fallback(start_fd, fds_to_keep, fds_to_keep_len);
}
#ifdef VFORK_USABLE
/* Reset dispositions for all signals to SIG_DFL except for ignored
* signals. This way we ensure that no signal handlers can run
* after we unblock signals in a child created by vfork().
*/
static void
reset_signal_handlers(const sigset_t *child_sigmask)
{
struct sigaction sa_dfl = {.sa_handler = SIG_DFL};
for (int sig = 1; sig < _NSIG; sig++) {
/* Dispositions for SIGKILL and SIGSTOP can't be changed. */
if (sig == SIGKILL || sig == SIGSTOP) {
continue;
}
/* There is no need to reset the disposition of signals that will
* remain blocked across execve() since the kernel will do it. */
if (sigismember(child_sigmask, sig) == 1) {
continue;
}
struct sigaction sa;
/* C libraries usually return EINVAL for signals used
* internally (e.g. for thread cancellation), so simply
* skip errors here. */
if (sigaction(sig, NULL, &sa) == -1) {
continue;
}
/* void *h works as these fields are both pointer types already. */
void *h = (sa.sa_flags & SA_SIGINFO ? (void *)sa.sa_sigaction :
(void *)sa.sa_handler);
if (h == SIG_IGN || h == SIG_DFL) {
continue;
}
/* This call can't reasonably fail, but if it does, terminating
* the child seems to be too harsh, so ignore errors. */
(void) sigaction(sig, &sa_dfl, NULL);
}
}
#endif /* VFORK_USABLE */
/*
* This function is code executed in the child process immediately after
* (v)fork to set things up and call exec().
*
* All of the code in this function must only use async-signal-safe functions,
* listed at `man 7 signal-safety` or
* http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
*
* This restriction is documented at
* http://www.opengroup.org/onlinepubs/009695399/functions/fork.html.
*
* If this function is called after vfork(), even more care must be taken.
* The lack of preparations that C libraries normally take on fork(),
* as well as sharing the address space with the parent, might make even
* async-signal-safe functions vfork-unsafe. In particular, on Linux,
* set*id() and setgroups() library functions must not be called, since
* they have to interact with the library-level thread list and send
* library-internal signals to implement per-process credentials semantics
* required by POSIX but not supported natively on Linux. Another reason to
* avoid this family of functions is that sharing an address space between
* processes running with different privileges is inherently insecure.
* See https://bugs.python.org/issue35823 for discussion and references.
*
* In some C libraries, setrlimit() has the same thread list/signalling
* behavior since resource limits were per-thread attributes before
* Linux 2.6.10. Musl, as of 1.2.1, is known to have this issue
* (https://www.openwall.com/lists/musl/2020/10/15/6).
*
* If vfork-unsafe functionality is desired after vfork(), consider using
* syscall() to obtain it.
*/
Py_NO_INLINE static void
child_exec(char *const exec_array[],
char *const argv[],
char *const envp[],
const char *cwd,
int p2cread, int p2cwrite,
int c2pread, int c2pwrite,
int errread, int errwrite,
int errpipe_read, int errpipe_write,
int close_fds, int restore_signals,
int call_setsid, pid_t pgid_to_set,
gid_t gid,
Py_ssize_t extra_group_size, const gid_t *extra_groups,
uid_t uid, int child_umask,
const void *child_sigmask,
int *fds_to_keep, Py_ssize_t fds_to_keep_len,
PyObject *preexec_fn,
PyObject *preexec_fn_args_tuple)
{
int i, saved_errno;
PyObject *result;
/* Indicate to the parent that the error happened before exec(). */
const char *err_msg = "noexec";
/* Buffer large enough to hold a hex integer. We can't malloc. */
char hex_errno[sizeof(saved_errno)*2+1];
if (make_inheritable(fds_to_keep, fds_to_keep_len, errpipe_write) < 0)
goto error;
/* Close parent's pipe ends. */
if (p2cwrite != -1)
POSIX_CALL(close(p2cwrite));
if (c2pread != -1)
POSIX_CALL(close(c2pread));
if (errread != -1)
POSIX_CALL(close(errread));
POSIX_CALL(close(errpipe_read));
/* When duping fds, if there arises a situation where one of the fds is
either 0, 1 or 2, it is possible that it is overwritten (#12607). */
if (c2pwrite == 0) {
POSIX_CALL(c2pwrite = dup(c2pwrite));
/* issue32270 */
if (_Py_set_inheritable_async_safe(c2pwrite, 0, NULL) < 0) {
goto error;
}
}
while (errwrite == 0 || errwrite == 1) {
POSIX_CALL(errwrite = dup(errwrite));
/* issue32270 */
if (_Py_set_inheritable_async_safe(errwrite, 0, NULL) < 0) {
goto error;
}
}
/* Dup fds for child.
dup2() removes the CLOEXEC flag but we must do it ourselves if dup2()
would be a no-op (issue #10806). */
if (p2cread == 0) {
if (_Py_set_inheritable_async_safe(p2cread, 1, NULL) < 0)
goto error;
}
else if (p2cread != -1)
POSIX_CALL(dup2(p2cread, 0)); /* stdin */
if (c2pwrite == 1) {
if (_Py_set_inheritable_async_safe(c2pwrite, 1, NULL) < 0)
goto error;
}
else if (c2pwrite != -1)
POSIX_CALL(dup2(c2pwrite, 1)); /* stdout */
if (errwrite == 2) {
if (_Py_set_inheritable_async_safe(errwrite, 1, NULL) < 0)
goto error;
}
else if (errwrite != -1)
POSIX_CALL(dup2(errwrite, 2)); /* stderr */
/* We no longer manually close p2cread, c2pwrite, and errwrite here as
* _close_open_fds takes care when it is not already non-inheritable. */
if (cwd) {
if (chdir(cwd) == -1) {
err_msg = "noexec:chdir";
goto error;
}
}
if (child_umask >= 0)
umask(child_umask); /* umask() always succeeds. */
if (restore_signals) {
_Py_RestoreSignals();
}
#ifdef VFORK_USABLE
if (child_sigmask) {
reset_signal_handlers(child_sigmask);
if ((errno = pthread_sigmask(SIG_SETMASK, child_sigmask, NULL))) {
goto error;
}
}
#endif
#ifdef HAVE_SETSID
if (call_setsid)
POSIX_CALL(setsid());
#endif
#ifdef HAVE_SETPGID
static_assert(_Py_IS_TYPE_SIGNED(pid_t), "pid_t is unsigned");
if (pgid_to_set >= 0) {
POSIX_CALL(setpgid(0, pgid_to_set));
}
#endif
#ifdef HAVE_SETGROUPS
if (extra_group_size >= 0) {
assert((extra_group_size == 0) == (extra_groups == NULL));
POSIX_CALL(setgroups(extra_group_size, extra_groups));
}
#endif /* HAVE_SETGROUPS */
#ifdef HAVE_SETREGID
if (gid != (gid_t)-1)
POSIX_CALL(setregid(gid, gid));
#endif /* HAVE_SETREGID */
#ifdef HAVE_SETREUID
if (uid != (uid_t)-1)
POSIX_CALL(setreuid(uid, uid));
#endif /* HAVE_SETREUID */
err_msg = "";
if (preexec_fn != Py_None && preexec_fn_args_tuple) {
/* This is where the user has asked us to deadlock their program. */
result = PyObject_Call(preexec_fn, preexec_fn_args_tuple, NULL);
if (result == NULL) {
/* Stringifying the exception or traceback would involve
* memory allocation and thus potential for deadlock.
* We've already faced potential deadlock by calling back
* into Python in the first place, so it probably doesn't
* matter but we avoid it to minimize the possibility. */
err_msg = "Exception occurred in preexec_fn.";
errno = 0; /* We don't want to report an OSError. */
goto error;
}
/* Py_DECREF(result); - We're about to exec so why bother? */
}
/* close FDs after executing preexec_fn, which might open FDs */
if (close_fds) {
/* TODO HP-UX could use pstat_getproc() if anyone cares about it. */
_close_open_fds(3, fds_to_keep, fds_to_keep_len);
}
/* This loop matches the Lib/os.py _execvpe()'s PATH search when */
/* given the executable_list generated by Lib/subprocess.py. */
saved_errno = 0;
for (i = 0; exec_array[i] != NULL; ++i) {
const char *executable = exec_array[i];
if (envp) {
execve(executable, argv, envp);
} else {
execv(executable, argv);
}
if (errno != ENOENT && errno != ENOTDIR && saved_errno == 0) {
saved_errno = errno;
}
}
/* Report the first exec error, not the last. */
if (saved_errno)
errno = saved_errno;
error:
saved_errno = errno;
/* Report the posix error to our parent process. */
/* We ignore all write() return values as the total size of our writes is
less than PIPEBUF and we cannot do anything about an error anyways.
Use _Py_write_noraise() to retry write() if it is interrupted by a
signal (fails with EINTR). */
if (saved_errno) {
char *cur;
_Py_write_noraise(errpipe_write, "OSError:", 8);
cur = hex_errno + sizeof(hex_errno);
while (saved_errno != 0 && cur != hex_errno) {
*--cur = Py_hexdigits[saved_errno % 16];
saved_errno /= 16;
}
_Py_write_noraise(errpipe_write, cur, hex_errno + sizeof(hex_errno) - cur);
_Py_write_noraise(errpipe_write, ":", 1);
/* We can't call strerror(saved_errno). It is not async signal safe.
* The parent process will look the error message up. */
} else {
_Py_write_noraise(errpipe_write, "SubprocessError:0:", 18);
}
_Py_write_noraise(errpipe_write, err_msg, strlen(err_msg));
}
/* The main purpose of this wrapper function is to isolate vfork() from both
* subprocess_fork_exec() and child_exec(). A child process created via
* vfork() executes on the same stack as the parent process while the latter is
* suspended, so this function should not be inlined to avoid compiler bugs
* that might clobber data needed by the parent later. Additionally,
* child_exec() should not be inlined to avoid spurious -Wclobber warnings from
* GCC (see bpo-35823).
*/
Py_NO_INLINE static pid_t
do_fork_exec(char *const exec_array[],
char *const argv[],
char *const envp[],
const char *cwd,
int p2cread, int p2cwrite,
int c2pread, int c2pwrite,
int errread, int errwrite,
int errpipe_read, int errpipe_write,
int close_fds, int restore_signals,
int call_setsid, pid_t pgid_to_set,
gid_t gid,
Py_ssize_t extra_group_size, const gid_t *extra_groups,
uid_t uid, int child_umask,
const void *child_sigmask,
int *fds_to_keep, Py_ssize_t fds_to_keep_len,
PyObject *preexec_fn,
PyObject *preexec_fn_args_tuple)
{
pid_t pid;
#ifdef VFORK_USABLE
PyThreadState *vfork_tstate_save;
if (child_sigmask) {
/* These are checked by our caller; verify them in debug builds. */
assert(uid == (uid_t)-1);
assert(gid == (gid_t)-1);
assert(extra_group_size < 0);
assert(preexec_fn == Py_None);
/* Drop the GIL so that other threads can continue execution while this
* thread in the parent remains blocked per vfork-semantics on the
* child's exec syscall outcome. Exec does filesystem access which
* can take an arbitrarily long time. This addresses GH-104372.
*
* The vfork'ed child still runs in our address space. Per POSIX it
* must be limited to nothing but exec, but the Linux implementation
* is a little more usable. See the child_exec() comment - The child
* MUST NOT re-acquire the GIL.
*/
vfork_tstate_save = PyEval_SaveThread();
pid = vfork();
if (pid != 0) {
// Not in the child process, reacquire the GIL.
PyEval_RestoreThread(vfork_tstate_save);
}
if (pid == (pid_t)-1) {
/* If vfork() fails, fall back to using fork(). When it isn't
* allowed in a process by the kernel, vfork can return -1
* with errno EINVAL. https://bugs.python.org/issue47151. */
pid = fork();
}
} else
#endif
{
pid = fork();
}
if (pid != 0) {
// Parent process.
return pid;
}
/* Child process.
* See the comment above child_exec() for restrictions imposed on
* the code below.
*/
if (preexec_fn != Py_None) {
/* We'll be calling back into Python later so we need to do this.
* This call may not be async-signal-safe but neither is calling
* back into Python. The user asked us to use hope as a strategy
* to avoid deadlock... */
PyOS_AfterFork_Child();
}
child_exec(exec_array, argv, envp, cwd,
p2cread, p2cwrite, c2pread, c2pwrite,
errread, errwrite, errpipe_read, errpipe_write,
close_fds, restore_signals, call_setsid, pgid_to_set,
gid, extra_group_size, extra_groups,
uid, child_umask, child_sigmask,
fds_to_keep, fds_to_keep_len,
preexec_fn, preexec_fn_args_tuple);
_exit(255);
return 0; /* Dead code to avoid a potential compiler warning. */
}
/*[clinic input]
@permit_long_docstring_body
_posixsubprocess.fork_exec as subprocess_fork_exec
args as process_args: object
executable_list: object
close_fds: bool
pass_fds as py_fds_to_keep: object(subclass_of='&PyTuple_Type')
cwd as cwd_obj: object
env as env_list: object
p2cread: int
p2cwrite: int
c2pread: int
c2pwrite: int
errread: int
errwrite: int
errpipe_read: int
errpipe_write: int
restore_signals: bool
call_setsid: bool
pgid_to_set: pid_t
gid as gid_object: object
extra_groups as extra_groups_packed: object
uid as uid_object: object
child_umask: int
preexec_fn: object
/
Spawn a fresh new child process.
Fork a child process, close parent file descriptors as appropriate in the
child and duplicate the few that are needed before calling exec() in the
child process.
If close_fds is True, close file descriptors 3 and higher, except those listed
in the sorted tuple pass_fds.
The preexec_fn, if supplied, will be called immediately before closing file