diff options
Diffstat (limited to 'Modules/_posixsubprocess.c')
| -rw-r--r-- | Modules/_posixsubprocess.c | 293 |
1 files changed, 258 insertions, 35 deletions
diff --git a/Modules/_posixsubprocess.c b/Modules/_posixsubprocess.c index 709ebaa..c3f7272 100644 --- a/Modules/_posixsubprocess.c +++ b/Modules/_posixsubprocess.c @@ -5,7 +5,26 @@ #endif #include <unistd.h> #include <fcntl.h> +#ifdef HAVE_SYS_TYPES_H +#include <sys/types.h> +#endif +#ifdef HAVE_SYS_SYSCALL_H +#include <sys/syscall.h> +#endif +#ifdef HAVE_DIRENT_H +#include <dirent.h> +#endif + +#if defined(sun) && !defined(HAVE_DIRFD) +/* Some versions of Solaris lack dirfd(). */ +# define DIRFD(dirp) ((dirp)->dd_fd) +# define HAVE_DIRFD +#else +# define DIRFD(dirp) (dirfd(dirp)) +#endif +#define LINUX_SOLARIS_FD_DIR "/proc/self/fd" +#define BSD_OSX_FD_DIR "/dev/fd" #define POSIX_CALL(call) if ((call) == -1) goto error @@ -26,6 +45,233 @@ static int _enable_gc(PyObject *gc_module) } +/* Convert ASCII to a positive int, no libc call. no overflow. -1 on error. */ +static int _pos_int_from_ascii(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; +} + + +/* 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, seq_len = PySequence_Length(fd_sequence); + long prev_fd = -1; + for (seq_idx = 0; seq_idx < seq_len; ++seq_idx) { + PyObject* py_fd = PySequence_Fast_GET_ITEM(fd_sequence, seq_idx); + long iter_fd = PyLong_AsLong(py_fd); + if (iter_fd < 0 || iter_fd < prev_fd || iter_fd > INT_MAX) { + /* Negative, overflow, not a Long, unsorted, too big for a fd. */ + return 1; + } + } + return 0; +} + + +/* Is fd found in the sorted Python Sequence? */ +static int _is_fd_in_sorted_fd_sequence(int fd, PyObject *fd_sequence) +{ + /* Binary search. */ + Py_ssize_t search_min = 0; + Py_ssize_t search_max = PySequence_Length(fd_sequence) - 1; + if (search_max < 0) + return 0; + do { + long middle = (search_min + search_max) / 2; + long middle_fd = PyLong_AsLong( + PySequence_Fast_GET_ITEM(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; +} + + +/* Close all file descriptors in the range start_fd inclusive to + * end_fd exclusive except for those in py_fds_to_keep. If the + * range defined by [start_fd, end_fd) is large this will take a + * long time as it calls close() on EVERY possible fd. + */ +static void _close_fds_by_brute_force(int start_fd, int end_fd, + PyObject *py_fds_to_keep) +{ + Py_ssize_t num_fds_to_keep = PySequence_Length(py_fds_to_keep); + Py_ssize_t keep_seq_idx; + int fd_num; + /* As py_fds_to_keep is sorted we can loop through the list closing + * fds inbetween any in the keep list falling within our range. */ + for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) { + PyObject* py_keep_fd = PySequence_Fast_GET_ITEM(py_fds_to_keep, + keep_seq_idx); + int keep_fd = PyLong_AsLong(py_keep_fd); + if (keep_fd < start_fd) + continue; + for (fd_num = start_fd; fd_num < keep_fd; ++fd_num) { + while (close(fd_num) < 0 && errno == EINTR); + } + start_fd = keep_fd + 1; + } + if (start_fd <= end_fd) { + for (fd_num = start_fd; fd_num < end_fd; ++fd_num) { + while (close(fd_num) < 0 && errno == EINTR); + } + } +} + + +#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_dirent { + unsigned long d_ino; /* Inode number */ + unsigned long d_off; /* Offset to next linux_dirent */ + unsigned short d_reclen; /* Length of this linux_dirent */ + char d_name[256]; /* Filename (null-terminated) */ +}; + +/* 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; + fd_dir_fd = open(LINUX_SOLARIS_FD_DIR, O_RDONLY | O_CLOEXEC, 0); + /* Not trying to open the BSD_OSX path as this is currently Linux only. */ + 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); + } +} + +#define _close_open_fd_range _close_open_fd_range_safe + +#else /* NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */ + + +/* 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(), readdir64() 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; + + proc_fd_dir = opendir(BSD_OSX_FD_DIR); + if (!proc_fd_dir) + proc_fd_dir = opendir(LINUX_SOLARIS_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 dirent64 *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; + /* readdir64 is used to work around Solaris 9 bug 6395699. */ + while ((dir_entry = readdir64(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); + } +} + +#define _close_open_fd_range _close_open_fd_range_maybe_unsafe + +#endif /* else NOT (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)) */ + + /* * This function is code executed in the child process immediately after fork * to set things up and call exec(). @@ -46,12 +292,12 @@ static void child_exec(char *const exec_array[], int errread, int errwrite, int errpipe_read, int errpipe_write, int close_fds, int restore_signals, - int call_setsid, Py_ssize_t num_fds_to_keep, + int call_setsid, PyObject *py_fds_to_keep, PyObject *preexec_fn, PyObject *preexec_fn_args_tuple) { - int i, saved_errno, fd_num, unused; + int i, saved_errno, unused; PyObject *result; const char* err_msg = ""; /* Buffer large enough to hold a hex integer. We can't malloc. */ @@ -113,33 +359,8 @@ static void child_exec(char *const exec_array[], POSIX_CALL(close(errwrite)); } - /* close() is intentionally not checked for errors here as we are closing */ - /* a large range of fds, some of which may be invalid. */ - if (close_fds) { - Py_ssize_t keep_seq_idx; - int start_fd = 3; - for (keep_seq_idx = 0; keep_seq_idx < num_fds_to_keep; ++keep_seq_idx) { - PyObject* py_keep_fd = PySequence_Fast_GET_ITEM(py_fds_to_keep, - keep_seq_idx); - int keep_fd = PyLong_AsLong(py_keep_fd); - if (keep_fd < 0) { /* Negative number, overflow or not a Long. */ - err_msg = "bad value in fds_to_keep."; - errno = 0; /* We don't want to report an OSError. */ - goto error; - } - if (keep_fd < start_fd) - continue; - for (fd_num = start_fd; fd_num < keep_fd; ++fd_num) { - close(fd_num); - } - start_fd = keep_fd + 1; - } - if (start_fd <= max_fd) { - for (fd_num = start_fd; fd_num < max_fd; ++fd_num) { - close(fd_num); - } - } - } + if (close_fds) + _close_open_fd_range(3, max_fd, py_fds_to_keep); if (cwd) POSIX_CALL(chdir(cwd)); @@ -227,7 +448,7 @@ subprocess_fork_exec(PyObject* self, PyObject *args) pid_t pid; int need_to_reenable_gc = 0; char *const *exec_array, *const *argv = NULL, *const *envp = NULL; - Py_ssize_t arg_num, num_fds_to_keep; + Py_ssize_t arg_num; if (!PyArg_ParseTuple( args, "OOOOOOiiiiiiiiiiO:fork_exec", @@ -243,9 +464,12 @@ subprocess_fork_exec(PyObject* self, PyObject *args) PyErr_SetString(PyExc_ValueError, "errpipe_write must be >= 3"); return NULL; } - num_fds_to_keep = PySequence_Length(py_fds_to_keep); - if (num_fds_to_keep < 0) { - PyErr_SetString(PyExc_ValueError, "bad fds_to_keep"); + if (PySequence_Length(py_fds_to_keep) < 0) { + PyErr_SetString(PyExc_ValueError, "cannot get length of fds_to_keep"); + 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; } @@ -348,8 +572,7 @@ subprocess_fork_exec(PyObject* self, PyObject *args) p2cread, p2cwrite, c2pread, c2pwrite, errread, errwrite, errpipe_read, errpipe_write, close_fds, restore_signals, call_setsid, - num_fds_to_keep, py_fds_to_keep, - preexec_fn, preexec_fn_args_tuple); + py_fds_to_keep, preexec_fn, preexec_fn_args_tuple); _exit(255); return NULL; /* Dead code to avoid a potential compiler warning. */ } |