/* Close all open file descriptors in the range start_fd inclusive to end_fd
* exclusive. Do not close any in the sorted py_fds_to_keep list.
*
* 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_fd_range_maybe_unsafe(int start_fd, int end_fd,
PyObject* py_fds_to_keep)
{
DIR *proc_fd_dir;
#ifndef HAVE_DIRFD
while (_is_fd_in_sorted_fd_sequence(start_fd, py_fds_to_keep) &&
(start_fd < end_fd)) {
++start_fd;
}
if (start_fd >= end_fd)
return;
/* 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. */
while (close(start_fd) < 0 && errno == EINTR);
++start_fd;
#endif
if (start_fd >= end_fd)
return;
#if defined(__FreeBSD__)
if (!_is_fdescfs_mounted_on_dev_fd())
proc_fd_dir = NULL;
else
#endif
proc_fd_dir = opendir(FD_DIR);
if (!proc_fd_dir) {
/* No way to get a list of open fds. */
_close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
} 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 && fd < end_fd &&
!_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
while (close(fd) < 0 && errno == EINTR);
}
errno = 0;
}
if (errno) {
/* readdir error, revert behavior. Highly Unlikely. */
_close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
}
closedir(proc_fd_dir);
}
}
/* Close all open file descriptors in the range from start_fd and higher
* Do not close any in the sorted py_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, PyObject* py_fds_to_keep)
{
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_fds_by_brute_force(start_fd, py_fds_to_keep);
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;
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, py_fds_to_keep)) {
close(fd);
}
}
}
close(fd_dir_fd);
}
}
/* Close all open file descriptors in the range start_fd inclusive to end_fd
* exclusive. Do not close any in the sorted py_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_fd_range_safe(int start_fd, int end_fd, PyObject* py_fds_to_keep)
{
int fd_dir_fd;
if (start_fd >= end_fd)
return;
#ifdef O_CLOEXEC
fd_dir_fd = open(FD_DIR, O_RDONLY | O_CLOEXEC, 0);
#else
fd_dir_fd = open(FD_DIR, O_RDONLY, 0);
#ifdef FD_CLOEXEC
{
int old = fcntl(fd_dir_fd, F_GETFD);
if (old != -1)
fcntl(fd_dir_fd, F_SETFD, old | FD_CLOEXEC);
}
#endif
#endif
if (fd_dir_fd == -1) {
/* No way to get a list of open fds. */
_close_fds_by_brute_force(start_fd, end_fd, py_fds_to_keep);
return;
} else {
char buffer[sizeof(struct linux_dirent)];
int bytes;
while ((bytes = syscall(SYS_getdents, fd_dir_fd,
(struct linux_dirent *)buffer,
sizeof(buffer))) > 0) {
struct linux_dirent *entry;
int offset;
for (offset = 0; offset < bytes; offset += entry->d_reclen) {
int fd;
entry = (struct linux_dirent *)(buffer + offset);
if ((fd = _pos_int_from_ascii(entry->d_name)) < 0)
continue; /* Not a number. */
if (fd != fd_dir_fd && fd >= start_fd && fd < end_fd &&
!_is_fd_in_sorted_fd_sequence(fd, py_fds_to_keep)) {
while (close(fd) < 0 && errno == EINTR);
}
}
}
close(fd_dir_fd);
}
}
