mirror of https://github.com/python/cpython
1073 lines
36 KiB
C
1073 lines
36 KiB
C
/* Authors: Gregory P. Smith & Jeffrey Yasskin */
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#include "Python.h"
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#include "pycore_fileutils.h"
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#if defined(HAVE_PIPE2) && !defined(_GNU_SOURCE)
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# define _GNU_SOURCE
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#endif
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#include <unistd.h>
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#include <fcntl.h>
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#ifdef HAVE_SYS_TYPES_H
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#include <sys/types.h>
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#endif
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#if defined(HAVE_SYS_STAT_H)
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#include <sys/stat.h>
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#endif
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#ifdef HAVE_SYS_SYSCALL_H
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#include <sys/syscall.h>
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#endif
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#if defined(HAVE_SYS_RESOURCE_H)
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#include <sys/resource.h>
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#endif
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#ifdef HAVE_DIRENT_H
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#include <dirent.h>
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#endif
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#ifdef HAVE_GRP_H
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#include <grp.h>
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#endif /* HAVE_GRP_H */
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#include "posixmodule.h"
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#ifdef _Py_MEMORY_SANITIZER
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# include <sanitizer/msan_interface.h>
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#endif
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#if defined(__ANDROID__) && __ANDROID_API__ < 21 && !defined(SYS_getdents64)
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# include <sys/linux-syscalls.h>
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# define SYS_getdents64 __NR_getdents64
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#endif
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#if defined(__linux__) && defined(HAVE_VFORK) && defined(HAVE_SIGNAL_H) && \
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defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
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/* If this is ever expanded to non-Linux platforms, verify what calls are
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* allowed after vfork(). Ex: setsid() may be disallowed on macOS? */
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# include <signal.h>
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# define VFORK_USABLE 1
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#endif
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#if defined(__sun) && defined(__SVR4)
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/* readdir64 is used to work around Solaris 9 bug 6395699. */
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# define readdir readdir64
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# define dirent dirent64
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# if !defined(HAVE_DIRFD)
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/* Some versions of Solaris lack dirfd(). */
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# define dirfd(dirp) ((dirp)->dd_fd)
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# define HAVE_DIRFD
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# endif
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#endif
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#if defined(__FreeBSD__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__DragonFly__)
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# define FD_DIR "/dev/fd"
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#else
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# define FD_DIR "/proc/self/fd"
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#endif
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#ifdef NGROUPS_MAX
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#define MAX_GROUPS NGROUPS_MAX
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#else
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#define MAX_GROUPS 64
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#endif
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#define POSIX_CALL(call) do { if ((call) == -1) goto error; } while (0)
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static struct PyModuleDef _posixsubprocessmodule;
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/* Convert ASCII to a positive int, no libc call. no overflow. -1 on error. */
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static int
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_pos_int_from_ascii(const char *name)
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{
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int num = 0;
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while (*name >= '0' && *name <= '9') {
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num = num * 10 + (*name - '0');
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++name;
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}
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if (*name)
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return -1; /* Non digit found, not a number. */
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return num;
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}
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#if defined(__FreeBSD__) || defined(__DragonFly__)
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/* When /dev/fd isn't mounted it is often a static directory populated
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* with 0 1 2 or entries for 0 .. 63 on FreeBSD, NetBSD, OpenBSD and DragonFlyBSD.
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* NetBSD and OpenBSD have a /proc fs available (though not necessarily
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* mounted) and do not have fdescfs for /dev/fd. MacOS X has a devfs
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* that properly supports /dev/fd.
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*/
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static int
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_is_fdescfs_mounted_on_dev_fd(void)
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{
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struct stat dev_stat;
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struct stat dev_fd_stat;
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if (stat("/dev", &dev_stat) != 0)
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return 0;
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if (stat(FD_DIR, &dev_fd_stat) != 0)
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return 0;
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if (dev_stat.st_dev == dev_fd_stat.st_dev)
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return 0; /* / == /dev == /dev/fd means it is static. #fail */
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return 1;
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}
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#endif
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/* Returns 1 if there is a problem with fd_sequence, 0 otherwise. */
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static int
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_sanity_check_python_fd_sequence(PyObject *fd_sequence)
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{
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Py_ssize_t seq_idx;
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long prev_fd = -1;
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for (seq_idx = 0; seq_idx < PyTuple_GET_SIZE(fd_sequence); ++seq_idx) {
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PyObject* py_fd = PyTuple_GET_ITEM(fd_sequence, seq_idx);
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long iter_fd;
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if (!PyLong_Check(py_fd)) {
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return 1;
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}
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iter_fd = PyLong_AsLong(py_fd);
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if (iter_fd < 0 || iter_fd <= prev_fd || iter_fd > INT_MAX) {
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/* Negative, overflow, unsorted, too big for a fd. */
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return 1;
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}
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prev_fd = iter_fd;
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}
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return 0;
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}
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/* Is fd found in the sorted Python Sequence? */
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static int
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_is_fd_in_sorted_fd_sequence(int fd, PyObject *fd_sequence)
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{
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/* Binary search. */
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Py_ssize_t search_min = 0;
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Py_ssize_t search_max = PyTuple_GET_SIZE(fd_sequence) - 1;
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if (search_max < 0)
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return 0;
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do {
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long middle = (search_min + search_max) / 2;
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long middle_fd = PyLong_AsLong(PyTuple_GET_ITEM(fd_sequence, middle));
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if (fd == middle_fd)
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return 1;
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if (fd > middle_fd)
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search_min = middle + 1;
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else
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search_max = middle - 1;
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} while (search_min <= search_max);
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return 0;
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}
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static int
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make_inheritable(PyObject *py_fds_to_keep, int errpipe_write)
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{
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Py_ssize_t i, len;
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len = PyTuple_GET_SIZE(py_fds_to_keep);
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for (i = 0; i < len; ++i) {
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PyObject* fdobj = PyTuple_GET_ITEM(py_fds_to_keep, i);
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long fd = PyLong_AsLong(fdobj);
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assert(!PyErr_Occurred());
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assert(0 <= fd && fd <= INT_MAX);
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if (fd == errpipe_write) {
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/* errpipe_write is part of py_fds_to_keep. It must be closed at
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exec(), but kept open in the child process until exec() is
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called. */
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continue;
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}
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if (_Py_set_inheritable_async_safe((int)fd, 1, NULL) < 0)
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return -1;
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}
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return 0;
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}
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/* Get the maximum file descriptor that could be opened by this process.
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* This function is async signal safe for use between fork() and exec().
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*/
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static long
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safe_get_max_fd(void)
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{
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long local_max_fd;
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#if defined(__NetBSD__)
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local_max_fd = fcntl(0, F_MAXFD);
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if (local_max_fd >= 0)
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return local_max_fd;
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#endif
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#if defined(HAVE_SYS_RESOURCE_H) && defined(__OpenBSD__)
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struct rlimit rl;
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/* Not on the POSIX async signal safe functions list but likely
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* safe. TODO - Someone should audit OpenBSD to make sure. */
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if (getrlimit(RLIMIT_NOFILE, &rl) >= 0)
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return (long) rl.rlim_max;
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#endif
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#ifdef _SC_OPEN_MAX
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local_max_fd = sysconf(_SC_OPEN_MAX);
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if (local_max_fd == -1)
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#endif
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local_max_fd = 256; /* Matches legacy Lib/subprocess.py behavior. */
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return local_max_fd;
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}
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/* Close all file descriptors in the range from start_fd and higher
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* except for those in py_fds_to_keep. If the range defined by
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* [start_fd, safe_get_max_fd()) is large this will take a long
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* time as it calls close() on EVERY possible fd.
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*
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* It isn't possible to know for sure what the max fd to go up to
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* is for processes with the capability of raising their maximum.
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*/
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static void
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_close_fds_by_brute_force(long start_fd, PyObject *py_fds_to_keep)
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{
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long end_fd = safe_get_max_fd();
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Py_ssize_t num_fds_to_keep = PyTuple_GET_SIZE(py_fds_to_keep);
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Py_ssize_t keep_seq_idx;
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/* As py_fds_to_keep is sorted we can loop through the list closing
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* fds in between any in the keep list falling within our range. */
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for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) {
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PyObject* py_keep_fd = PyTuple_GET_ITEM(py_fds_to_keep, keep_seq_idx);
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int keep_fd = PyLong_AsLong(py_keep_fd);
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if (keep_fd < start_fd)
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continue;
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_Py_closerange(start_fd, keep_fd - 1);
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start_fd = keep_fd + 1;
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}
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if (start_fd <= end_fd) {
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_Py_closerange(start_fd, end_fd);
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}
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}
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#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
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/* It doesn't matter if d_name has room for NAME_MAX chars; we're using this
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* only to read a directory of short file descriptor number names. The kernel
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* will return an error if we didn't give it enough space. Highly Unlikely.
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* This structure is very old and stable: It will not change unless the kernel
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* chooses to break compatibility with all existing binaries. Highly Unlikely.
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*/
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struct linux_dirent64 {
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unsigned long long d_ino;
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long long d_off;
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unsigned short d_reclen; /* Length of this linux_dirent */
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unsigned char d_type;
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char d_name[256]; /* Filename (null-terminated) */
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};
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/* Close all open file descriptors in the range from start_fd and higher
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* Do not close any in the sorted py_fds_to_keep list.
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*
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* This version is async signal safe as it does not make any unsafe C library
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* calls, malloc calls or handle any locks. It is _unfortunate_ to be forced
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* to resort to making a kernel system call directly but this is the ONLY api
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* available that does no harm. opendir/readdir/closedir perform memory
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* allocation and locking so while they usually work they are not guaranteed
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* to (especially if you have replaced your malloc implementation). A version
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* of this function that uses those can be found in the _maybe_unsafe variant.
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*
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* This is Linux specific because that is all I am ready to test it on. It
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* should be easy to add OS specific dirent or dirent64 structures and modify
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* it with some cpp #define magic to work on other OSes as well if you want.
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*/
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static void
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_close_open_fds_safe(int start_fd, PyObject* py_fds_to_keep)
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{
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int fd_dir_fd;
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fd_dir_fd = _Py_open_noraise(FD_DIR, O_RDONLY);
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if (fd_dir_fd == -1) {
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/* No way to get a list of open fds. */
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_close_fds_by_brute_force(start_fd, py_fds_to_keep);
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return;
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} else {
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char buffer[sizeof(struct linux_dirent64)];
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int bytes;
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while ((bytes = syscall(SYS_getdents64, fd_dir_fd,
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(struct linux_dirent64 *)buffer,
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sizeof(buffer))) > 0) {
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struct linux_dirent64 *entry;
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int offset;
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#ifdef _Py_MEMORY_SANITIZER
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__msan_unpoison(buffer, bytes);
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#endif
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for (offset = 0; offset < bytes; offset += entry->d_reclen) {
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int fd;
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entry = (struct linux_dirent64 *)(buffer + offset);
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if ((fd = _pos_int_from_ascii(entry->d_name)) < 0)
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continue; /* Not a number. */
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if (fd != fd_dir_fd && fd >= start_fd &&
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!_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
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close(fd);
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}
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}
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}
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close(fd_dir_fd);
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}
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}
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#define _close_open_fds _close_open_fds_safe
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#else /* NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
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/* Close all open file descriptors from start_fd and higher.
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* Do not close any in the sorted py_fds_to_keep tuple.
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*
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* This function violates the strict use of async signal safe functions. :(
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* It calls opendir(), readdir() and closedir(). Of these, the one most
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* likely to ever cause a problem is opendir() as it performs an internal
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* malloc(). Practically this should not be a problem. The Java VM makes the
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* same calls between fork and exec in its own UNIXProcess_md.c implementation.
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*
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* readdir_r() is not used because it provides no benefit. It is typically
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* implemented as readdir() followed by memcpy(). See also:
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* http://womble.decadent.org.uk/readdir_r-advisory.html
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*/
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static void
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_close_open_fds_maybe_unsafe(long start_fd, PyObject* py_fds_to_keep)
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{
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DIR *proc_fd_dir;
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#ifndef HAVE_DIRFD
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while (_is_fd_in_sorted_fd_sequence(start_fd, py_fds_to_keep)) {
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++start_fd;
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}
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/* Close our lowest fd before we call opendir so that it is likely to
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* reuse that fd otherwise we might close opendir's file descriptor in
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* our loop. This trick assumes that fd's are allocated on a lowest
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* available basis. */
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close(start_fd);
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++start_fd;
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#endif
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#if defined(__FreeBSD__) || defined(__DragonFly__)
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if (!_is_fdescfs_mounted_on_dev_fd())
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proc_fd_dir = NULL;
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else
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#endif
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proc_fd_dir = opendir(FD_DIR);
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if (!proc_fd_dir) {
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/* No way to get a list of open fds. */
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_close_fds_by_brute_force(start_fd, py_fds_to_keep);
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} else {
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struct dirent *dir_entry;
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#ifdef HAVE_DIRFD
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int fd_used_by_opendir = dirfd(proc_fd_dir);
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#else
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int fd_used_by_opendir = start_fd - 1;
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#endif
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errno = 0;
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while ((dir_entry = readdir(proc_fd_dir))) {
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int fd;
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if ((fd = _pos_int_from_ascii(dir_entry->d_name)) < 0)
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continue; /* Not a number. */
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if (fd != fd_used_by_opendir && fd >= start_fd &&
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!_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
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close(fd);
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}
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errno = 0;
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}
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if (errno) {
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/* readdir error, revert behavior. Highly Unlikely. */
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_close_fds_by_brute_force(start_fd, py_fds_to_keep);
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}
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closedir(proc_fd_dir);
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}
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}
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#define _close_open_fds _close_open_fds_maybe_unsafe
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#endif /* else NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */
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#ifdef VFORK_USABLE
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/* Reset dispositions for all signals to SIG_DFL except for ignored
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* signals. This way we ensure that no signal handlers can run
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* after we unblock signals in a child created by vfork().
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*/
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static void
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reset_signal_handlers(const sigset_t *child_sigmask)
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{
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struct sigaction sa_dfl = {.sa_handler = SIG_DFL};
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for (int sig = 1; sig < _NSIG; sig++) {
|
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/* Dispositions for SIGKILL and SIGSTOP can't be changed. */
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if (sig == SIGKILL || sig == SIGSTOP) {
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continue;
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}
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/* There is no need to reset the disposition of signals that will
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* remain blocked across execve() since the kernel will do it. */
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if (sigismember(child_sigmask, sig) == 1) {
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continue;
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}
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struct sigaction sa;
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/* C libraries usually return EINVAL for signals used
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* internally (e.g. for thread cancellation), so simply
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* skip errors here. */
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if (sigaction(sig, NULL, &sa) == -1) {
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continue;
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}
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/* void *h works as these fields are both pointer types already. */
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void *h = (sa.sa_flags & SA_SIGINFO ? (void *)sa.sa_sigaction :
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(void *)sa.sa_handler);
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if (h == SIG_IGN || h == SIG_DFL) {
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continue;
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}
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|
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/* This call can't reasonably fail, but if it does, terminating
|
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* the child seems to be too harsh, so ignore errors. */
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(void) sigaction(sig, &sa_dfl, NULL);
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}
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}
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#endif /* VFORK_USABLE */
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|
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|
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/*
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* This function is code executed in the child process immediately after
|
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* (v)fork to set things up and call exec().
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*
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* All of the code in this function must only use async-signal-safe functions,
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* listed at `man 7 signal` or
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* http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html.
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*
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* This restriction is documented at
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* http://www.opengroup.org/onlinepubs/009695399/functions/fork.html.
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*
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* If this function is called after vfork(), even more care must be taken.
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* The lack of preparations that C libraries normally take on fork(),
|
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* as well as sharing the address space with the parent, might make even
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* async-signal-safe functions vfork-unsafe. In particular, on Linux,
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|
* set*id() and setgroups() library functions must not be called, since
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* 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
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* avoid this family of functions is that sharing an address space between
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* processes running with different privileges is inherently insecure.
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|
* See bpo-35823 for further discussion and references.
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*
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* 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
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|
* (https://www.openwall.com/lists/musl/2020/10/15/6).
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*
|
|
* If vfork-unsafe functionality is desired after vfork(), consider using
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* syscall() to obtain it.
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|
*/
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|
Py_NO_INLINE static void
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|
child_exec(char *const exec_array[],
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|
char *const argv[],
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|
char *const envp[],
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|
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,
|
|
int call_setgid, gid_t gid,
|
|
int call_setgroups, size_t groups_size, const gid_t *groups,
|
|
int call_setuid, uid_t uid, int child_umask,
|
|
const void *child_sigmask,
|
|
PyObject *py_fds_to_keep,
|
|
PyObject *preexec_fn,
|
|
PyObject *preexec_fn_args_tuple)
|
|
{
|
|
int i, saved_errno, reached_preexec = 0;
|
|
PyObject *result;
|
|
const char* err_msg = "";
|
|
/* Buffer large enough to hold a hex integer. We can't malloc. */
|
|
char hex_errno[sizeof(saved_errno)*2+1];
|
|
|
|
if (make_inheritable(py_fds_to_keep, 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)
|
|
POSIX_CALL(chdir(cwd));
|
|
|
|
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_SETGROUPS
|
|
if (call_setgroups)
|
|
POSIX_CALL(setgroups(groups_size, groups));
|
|
#endif /* HAVE_SETGROUPS */
|
|
|
|
#ifdef HAVE_SETREGID
|
|
if (call_setgid)
|
|
POSIX_CALL(setregid(gid, gid));
|
|
#endif /* HAVE_SETREGID */
|
|
|
|
#ifdef HAVE_SETREUID
|
|
if (call_setuid)
|
|
POSIX_CALL(setreuid(uid, uid));
|
|
#endif /* HAVE_SETREUID */
|
|
|
|
|
|
reached_preexec = 1;
|
|
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, py_fds_to_keep);
|
|
}
|
|
|
|
/* 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);
|
|
if (!reached_preexec) {
|
|
/* Indicate to the parent that the error happened before exec(). */
|
|
_Py_write_noraise(errpipe_write, "noexec", 6);
|
|
}
|
|
/* 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,
|
|
int call_setgid, gid_t gid,
|
|
int call_setgroups, size_t groups_size, const gid_t *groups,
|
|
int call_setuid, uid_t uid, int child_umask,
|
|
const void *child_sigmask,
|
|
PyObject *py_fds_to_keep,
|
|
PyObject *preexec_fn,
|
|
PyObject *preexec_fn_args_tuple)
|
|
{
|
|
|
|
pid_t pid;
|
|
|
|
#ifdef VFORK_USABLE
|
|
if (child_sigmask) {
|
|
/* These are checked by our caller; verify them in debug builds. */
|
|
assert(!call_setuid);
|
|
assert(!call_setgid);
|
|
assert(!call_setgroups);
|
|
assert(preexec_fn == Py_None);
|
|
|
|
pid = vfork();
|
|
} else
|
|
#endif
|
|
{
|
|
pid = fork();
|
|
}
|
|
|
|
if (pid != 0) {
|
|
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,
|
|
call_setgid, gid, call_setgroups, groups_size, groups,
|
|
call_setuid, uid, child_umask, child_sigmask,
|
|
py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);
|
|
_exit(255);
|
|
return 0; /* Dead code to avoid a potential compiler warning. */
|
|
}
|
|
|
|
|
|
static PyObject *
|
|
subprocess_fork_exec(PyObject *module, PyObject *args)
|
|
{
|
|
PyObject *gc_module = NULL;
|
|
PyObject *executable_list, *py_fds_to_keep;
|
|
PyObject *env_list, *preexec_fn;
|
|
PyObject *process_args, *converted_args = NULL, *fast_args = NULL;
|
|
PyObject *preexec_fn_args_tuple = NULL;
|
|
PyObject *groups_list;
|
|
PyObject *uid_object, *gid_object;
|
|
int p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite;
|
|
int errpipe_read, errpipe_write, close_fds, restore_signals;
|
|
int call_setsid;
|
|
int call_setgid = 0, call_setgroups = 0, call_setuid = 0;
|
|
uid_t uid;
|
|
gid_t gid, *groups = NULL;
|
|
int child_umask;
|
|
PyObject *cwd_obj, *cwd_obj2 = NULL;
|
|
const char *cwd;
|
|
pid_t pid = -1;
|
|
int need_to_reenable_gc = 0;
|
|
char *const *exec_array, *const *argv = NULL, *const *envp = NULL;
|
|
Py_ssize_t arg_num, num_groups = 0;
|
|
int need_after_fork = 0;
|
|
int saved_errno = 0;
|
|
|
|
if (!PyArg_ParseTuple(
|
|
args, "OOpO!OOiiiiiiiiiiOOOiO:fork_exec",
|
|
&process_args, &executable_list,
|
|
&close_fds, &PyTuple_Type, &py_fds_to_keep,
|
|
&cwd_obj, &env_list,
|
|
&p2cread, &p2cwrite, &c2pread, &c2pwrite,
|
|
&errread, &errwrite, &errpipe_read, &errpipe_write,
|
|
&restore_signals, &call_setsid,
|
|
&gid_object, &groups_list, &uid_object, &child_umask,
|
|
&preexec_fn))
|
|
return NULL;
|
|
|
|
if ((preexec_fn != Py_None) &&
|
|
(PyInterpreterState_Get() != PyInterpreterState_Main())) {
|
|
PyErr_SetString(PyExc_RuntimeError,
|
|
"preexec_fn not supported within subinterpreters");
|
|
return NULL;
|
|
}
|
|
|
|
if (close_fds && errpipe_write < 3) { /* precondition */
|
|
PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3");
|
|
return NULL;
|
|
}
|
|
if (_sanity_check_python_fd_sequence(py_fds_to_keep)) {
|
|
PyErr_SetString(PyExc_ValueError, "bad value(s) in fds_to_keep");
|
|
return NULL;
|
|
}
|
|
|
|
PyInterpreterState *interp = PyInterpreterState_Get();
|
|
const PyConfig *config = _PyInterpreterState_GetConfig(interp);
|
|
if (config->_isolated_interpreter) {
|
|
PyErr_SetString(PyExc_RuntimeError,
|
|
"subprocess not supported for isolated subinterpreters");
|
|
return NULL;
|
|
}
|
|
|
|
/* We need to call gc.disable() when we'll be calling preexec_fn */
|
|
if (preexec_fn != Py_None) {
|
|
need_to_reenable_gc = PyGC_Disable();
|
|
}
|
|
|
|
exec_array = _PySequence_BytesToCharpArray(executable_list);
|
|
if (!exec_array)
|
|
goto cleanup;
|
|
|
|
/* Convert args and env into appropriate arguments for exec() */
|
|
/* These conversions are done in the parent process to avoid allocating
|
|
or freeing memory in the child process. */
|
|
if (process_args != Py_None) {
|
|
Py_ssize_t num_args;
|
|
/* Equivalent to: */
|
|
/* tuple(PyUnicode_FSConverter(arg) for arg in process_args) */
|
|
fast_args = PySequence_Fast(process_args, "argv must be a tuple");
|
|
if (fast_args == NULL)
|
|
goto cleanup;
|
|
num_args = PySequence_Fast_GET_SIZE(fast_args);
|
|
converted_args = PyTuple_New(num_args);
|
|
if (converted_args == NULL)
|
|
goto cleanup;
|
|
for (arg_num = 0; arg_num < num_args; ++arg_num) {
|
|
PyObject *borrowed_arg, *converted_arg;
|
|
if (PySequence_Fast_GET_SIZE(fast_args) != num_args) {
|
|
PyErr_SetString(PyExc_RuntimeError, "args changed during iteration");
|
|
goto cleanup;
|
|
}
|
|
borrowed_arg = PySequence_Fast_GET_ITEM(fast_args, arg_num);
|
|
if (PyUnicode_FSConverter(borrowed_arg, &converted_arg) == 0)
|
|
goto cleanup;
|
|
PyTuple_SET_ITEM(converted_args, arg_num, converted_arg);
|
|
}
|
|
|
|
argv = _PySequence_BytesToCharpArray(converted_args);
|
|
Py_CLEAR(converted_args);
|
|
Py_CLEAR(fast_args);
|
|
if (!argv)
|
|
goto cleanup;
|
|
}
|
|
|
|
if (env_list != Py_None) {
|
|
envp = _PySequence_BytesToCharpArray(env_list);
|
|
if (!envp)
|
|
goto cleanup;
|
|
}
|
|
|
|
if (cwd_obj != Py_None) {
|
|
if (PyUnicode_FSConverter(cwd_obj, &cwd_obj2) == 0)
|
|
goto cleanup;
|
|
cwd = PyBytes_AsString(cwd_obj2);
|
|
} else {
|
|
cwd = NULL;
|
|
}
|
|
|
|
if (groups_list != Py_None) {
|
|
#ifdef HAVE_SETGROUPS
|
|
Py_ssize_t i;
|
|
gid_t gid;
|
|
|
|
if (!PyList_Check(groups_list)) {
|
|
PyErr_SetString(PyExc_TypeError,
|
|
"setgroups argument must be a list");
|
|
goto cleanup;
|
|
}
|
|
num_groups = PySequence_Size(groups_list);
|
|
|
|
if (num_groups < 0)
|
|
goto cleanup;
|
|
|
|
if (num_groups > MAX_GROUPS) {
|
|
PyErr_SetString(PyExc_ValueError, "too many groups");
|
|
goto cleanup;
|
|
}
|
|
|
|
if ((groups = PyMem_RawMalloc(num_groups * sizeof(gid_t))) == NULL) {
|
|
PyErr_SetString(PyExc_MemoryError,
|
|
"failed to allocate memory for group list");
|
|
goto cleanup;
|
|
}
|
|
|
|
for (i = 0; i < num_groups; i++) {
|
|
PyObject *elem;
|
|
elem = PySequence_GetItem(groups_list, i);
|
|
if (!elem)
|
|
goto cleanup;
|
|
if (!PyLong_Check(elem)) {
|
|
PyErr_SetString(PyExc_TypeError,
|
|
"groups must be integers");
|
|
Py_DECREF(elem);
|
|
goto cleanup;
|
|
} else {
|
|
if (!_Py_Gid_Converter(elem, &gid)) {
|
|
Py_DECREF(elem);
|
|
PyErr_SetString(PyExc_ValueError, "invalid group id");
|
|
goto cleanup;
|
|
}
|
|
groups[i] = gid;
|
|
}
|
|
Py_DECREF(elem);
|
|
}
|
|
call_setgroups = 1;
|
|
|
|
#else /* HAVE_SETGROUPS */
|
|
PyErr_BadInternalCall();
|
|
goto cleanup;
|
|
#endif /* HAVE_SETGROUPS */
|
|
}
|
|
|
|
if (gid_object != Py_None) {
|
|
#ifdef HAVE_SETREGID
|
|
if (!_Py_Gid_Converter(gid_object, &gid))
|
|
goto cleanup;
|
|
|
|
call_setgid = 1;
|
|
|
|
#else /* HAVE_SETREGID */
|
|
PyErr_BadInternalCall();
|
|
goto cleanup;
|
|
#endif /* HAVE_SETREUID */
|
|
}
|
|
|
|
if (uid_object != Py_None) {
|
|
#ifdef HAVE_SETREUID
|
|
if (!_Py_Uid_Converter(uid_object, &uid))
|
|
goto cleanup;
|
|
|
|
call_setuid = 1;
|
|
|
|
#else /* HAVE_SETREUID */
|
|
PyErr_BadInternalCall();
|
|
goto cleanup;
|
|
#endif /* HAVE_SETREUID */
|
|
}
|
|
|
|
/* This must be the last thing done before fork() because we do not
|
|
* want to call PyOS_BeforeFork() if there is any chance of another
|
|
* error leading to the cleanup: code without calling fork(). */
|
|
if (preexec_fn != Py_None) {
|
|
preexec_fn_args_tuple = PyTuple_New(0);
|
|
if (!preexec_fn_args_tuple)
|
|
goto cleanup;
|
|
PyOS_BeforeFork();
|
|
need_after_fork = 1;
|
|
}
|
|
|
|
/* NOTE: When old_sigmask is non-NULL, do_fork_exec() may use vfork(). */
|
|
const void *old_sigmask = NULL;
|
|
#ifdef VFORK_USABLE
|
|
/* Use vfork() only if it's safe. See the comment above child_exec(). */
|
|
sigset_t old_sigs;
|
|
if (preexec_fn == Py_None &&
|
|
!call_setuid && !call_setgid && !call_setgroups) {
|
|
/* Block all signals to ensure that no signal handlers are run in the
|
|
* child process while it shares memory with us. Note that signals
|
|
* used internally by C libraries won't be blocked by
|
|
* pthread_sigmask(), but signal handlers installed by C libraries
|
|
* normally service only signals originating from *within the process*,
|
|
* so it should be sufficient to consider any library function that
|
|
* might send such a signal to be vfork-unsafe and do not call it in
|
|
* the child.
|
|
*/
|
|
sigset_t all_sigs;
|
|
sigfillset(&all_sigs);
|
|
if ((saved_errno = pthread_sigmask(SIG_BLOCK, &all_sigs, &old_sigs))) {
|
|
goto cleanup;
|
|
}
|
|
old_sigmask = &old_sigs;
|
|
}
|
|
#endif
|
|
|
|
pid = do_fork_exec(exec_array, argv, envp, cwd,
|
|
p2cread, p2cwrite, c2pread, c2pwrite,
|
|
errread, errwrite, errpipe_read, errpipe_write,
|
|
close_fds, restore_signals, call_setsid,
|
|
call_setgid, gid, call_setgroups, num_groups, groups,
|
|
call_setuid, uid, child_umask, old_sigmask,
|
|
py_fds_to_keep, preexec_fn, preexec_fn_args_tuple);
|
|
|
|
/* Parent (original) process */
|
|
if (pid == -1) {
|
|
/* Capture errno for the exception. */
|
|
saved_errno = errno;
|
|
}
|
|
|
|
#ifdef VFORK_USABLE
|
|
if (old_sigmask) {
|
|
/* vfork() semantics guarantees that the parent is blocked
|
|
* until the child performs _exit() or execve(), so it is safe
|
|
* to unblock signals once we're here.
|
|
* Note that in environments where vfork() is implemented as fork(),
|
|
* such as QEMU user-mode emulation, the parent won't be blocked,
|
|
* but it won't share the address space with the child,
|
|
* so it's still safe to unblock the signals.
|
|
*
|
|
* We don't handle errors here because this call can't fail
|
|
* if valid arguments are given, and because there is no good
|
|
* way for the caller to deal with a failure to restore
|
|
* the thread signal mask. */
|
|
(void) pthread_sigmask(SIG_SETMASK, old_sigmask, NULL);
|
|
}
|
|
#endif
|
|
|
|
if (need_after_fork)
|
|
PyOS_AfterFork_Parent();
|
|
|
|
cleanup:
|
|
if (saved_errno != 0) {
|
|
errno = saved_errno;
|
|
/* We can't call this above as PyOS_AfterFork_Parent() calls back
|
|
* into Python code which would see the unreturned error. */
|
|
PyErr_SetFromErrno(PyExc_OSError);
|
|
}
|
|
|
|
Py_XDECREF(preexec_fn_args_tuple);
|
|
PyMem_RawFree(groups);
|
|
Py_XDECREF(cwd_obj2);
|
|
if (envp)
|
|
_Py_FreeCharPArray(envp);
|
|
Py_XDECREF(converted_args);
|
|
Py_XDECREF(fast_args);
|
|
if (argv)
|
|
_Py_FreeCharPArray(argv);
|
|
if (exec_array)
|
|
_Py_FreeCharPArray(exec_array);
|
|
|
|
if (need_to_reenable_gc) {
|
|
PyGC_Enable();
|
|
}
|
|
Py_XDECREF(gc_module);
|
|
|
|
return pid == -1 ? NULL : PyLong_FromPid(pid);
|
|
}
|
|
|
|
|
|
PyDoc_STRVAR(subprocess_fork_exec_doc,
|
|
"fork_exec(args, executable_list, close_fds, pass_fds, cwd, env,\n\
|
|
p2cread, p2cwrite, c2pread, c2pwrite,\n\
|
|
errread, errwrite, errpipe_read, errpipe_write,\n\
|
|
restore_signals, call_setsid,\n\
|
|
gid, groups_list, uid,\n\
|
|
preexec_fn)\n\
|
|
\n\
|
|
Forks a child process, closes parent file descriptors as appropriate in the\n\
|
|
child and dups the few that are needed before calling exec() in the child\n\
|
|
process.\n\
|
|
\n\
|
|
If close_fds is true, close file descriptors 3 and higher, except those listed\n\
|
|
in the sorted tuple pass_fds.\n\
|
|
\n\
|
|
The preexec_fn, if supplied, will be called immediately before closing file\n\
|
|
descriptors and exec.\n\
|
|
WARNING: preexec_fn is NOT SAFE if your application uses threads.\n\
|
|
It may trigger infrequent, difficult to debug deadlocks.\n\
|
|
\n\
|
|
If an error occurs in the child process before the exec, it is\n\
|
|
serialized and written to the errpipe_write fd per subprocess.py.\n\
|
|
\n\
|
|
Returns: the child process's PID.\n\
|
|
\n\
|
|
Raises: Only on an error in the parent process.\n\
|
|
");
|
|
|
|
/* module level code ********************************************************/
|
|
|
|
PyDoc_STRVAR(module_doc,
|
|
"A POSIX helper for the subprocess module.");
|
|
|
|
static PyMethodDef module_methods[] = {
|
|
{"fork_exec", subprocess_fork_exec, METH_VARARGS, subprocess_fork_exec_doc},
|
|
{NULL, NULL} /* sentinel */
|
|
};
|
|
|
|
static PyModuleDef_Slot _posixsubprocess_slots[] = {
|
|
{0, NULL}
|
|
};
|
|
|
|
static struct PyModuleDef _posixsubprocessmodule = {
|
|
PyModuleDef_HEAD_INIT,
|
|
.m_name = "_posixsubprocess",
|
|
.m_doc = module_doc,
|
|
.m_size = 0,
|
|
.m_methods = module_methods,
|
|
.m_slots = _posixsubprocess_slots,
|
|
};
|
|
|
|
PyMODINIT_FUNC
|
|
PyInit__posixsubprocess(void)
|
|
{
|
|
return PyModuleDef_Init(&_posixsubprocessmodule);
|
|
}
|