727 lines
23 KiB
C
727 lines
23 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/resource.h>
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#include <sys/socket.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "dirent-util.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "fs-util.h"
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#include "macro.h"
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#include "memfd-util.h"
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#include "missing.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "process-util.h"
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#include "socket-util.h"
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#include "stdio-util.h"
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#include "util.h"
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int close_nointr(int fd) {
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assert(fd >= 0);
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if (close(fd) >= 0)
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return 0;
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/*
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* Just ignore EINTR; a retry loop is the wrong thing to do on
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* Linux.
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*
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* http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
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* https://bugzilla.gnome.org/show_bug.cgi?id=682819
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* http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR
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* https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain
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*/
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if (errno == EINTR)
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return 0;
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return -errno;
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}
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int safe_close(int fd) {
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/*
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* Like close_nointr() but cannot fail. Guarantees errno is
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* unchanged. Is a NOP with negative fds passed, and returns
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* -1, so that it can be used in this syntax:
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*
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* fd = safe_close(fd);
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*/
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if (fd >= 0) {
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PROTECT_ERRNO;
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/* The kernel might return pretty much any error code
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* via close(), but the fd will be closed anyway. The
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* only condition we want to check for here is whether
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* the fd was invalid at all... */
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assert_se(close_nointr(fd) != -EBADF);
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}
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return -1;
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}
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void safe_close_pair(int p[]) {
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assert(p);
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if (p[0] == p[1]) {
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/* Special case pairs which use the same fd in both
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* directions... */
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p[0] = p[1] = safe_close(p[0]);
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return;
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}
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p[0] = safe_close(p[0]);
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p[1] = safe_close(p[1]);
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}
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void close_many(const int fds[], unsigned n_fd) {
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unsigned i;
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assert(fds || n_fd <= 0);
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for (i = 0; i < n_fd; i++)
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safe_close(fds[i]);
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}
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int fclose_nointr(FILE *f) {
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assert(f);
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/* Same as close_nointr(), but for fclose() */
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if (fclose(f) == 0)
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return 0;
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if (errno == EINTR)
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return 0;
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return -errno;
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}
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FILE* safe_fclose(FILE *f) {
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/* Same as safe_close(), but for fclose() */
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if (f) {
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PROTECT_ERRNO;
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assert_se(fclose_nointr(f) != EBADF);
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}
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return NULL;
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}
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DIR* safe_closedir(DIR *d) {
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if (d) {
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PROTECT_ERRNO;
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assert_se(closedir(d) >= 0 || errno != EBADF);
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}
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return NULL;
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}
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int fd_nonblock(int fd, bool nonblock) {
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int flags, nflags;
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assert(fd >= 0);
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flags = fcntl(fd, F_GETFL, 0);
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if (flags < 0)
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return -errno;
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if (nonblock)
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nflags = flags | O_NONBLOCK;
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else
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nflags = flags & ~O_NONBLOCK;
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if (nflags == flags)
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return 0;
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if (fcntl(fd, F_SETFL, nflags) < 0)
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return -errno;
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return 0;
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}
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int fd_cloexec(int fd, bool cloexec) {
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int flags, nflags;
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assert(fd >= 0);
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flags = fcntl(fd, F_GETFD, 0);
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if (flags < 0)
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return -errno;
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if (cloexec)
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nflags = flags | FD_CLOEXEC;
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else
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nflags = flags & ~FD_CLOEXEC;
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if (nflags == flags)
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return 0;
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if (fcntl(fd, F_SETFD, nflags) < 0)
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return -errno;
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return 0;
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}
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_pure_ static bool fd_in_set(int fd, const int fdset[], unsigned n_fdset) {
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unsigned i;
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assert(n_fdset == 0 || fdset);
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for (i = 0; i < n_fdset; i++)
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if (fdset[i] == fd)
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return true;
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return false;
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}
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int close_all_fds(const int except[], unsigned n_except) {
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_cleanup_closedir_ DIR *d = NULL;
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struct dirent *de;
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int r = 0;
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assert(n_except == 0 || except);
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d = opendir("/proc/self/fd");
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if (!d) {
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int fd;
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struct rlimit rl;
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/* When /proc isn't available (for example in chroots)
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* the fallback is brute forcing through the fd
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* table */
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assert_se(getrlimit(RLIMIT_NOFILE, &rl) >= 0);
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for (fd = 3; fd < (int) rl.rlim_max; fd ++) {
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int q;
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if (fd_in_set(fd, except, n_except))
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continue;
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q = close_nointr(fd);
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if (q < 0 && q != -EBADF && r >= 0)
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r = q;
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}
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return r;
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}
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FOREACH_DIRENT(de, d, return -errno) {
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int fd = -1, q;
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if (safe_atoi(de->d_name, &fd) < 0)
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/* Let's better ignore this, just in case */
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continue;
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if (fd < 3)
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continue;
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if (fd == dirfd(d))
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continue;
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if (fd_in_set(fd, except, n_except))
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continue;
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q = close_nointr(fd);
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if (q < 0 && q != -EBADF && r >= 0) /* Valgrind has its own FD and doesn't want to have it closed */
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r = q;
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}
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return r;
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}
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int same_fd(int a, int b) {
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struct stat sta, stb;
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pid_t pid;
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int r, fa, fb;
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assert(a >= 0);
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assert(b >= 0);
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/* Compares two file descriptors. Note that semantics are
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* quite different depending on whether we have kcmp() or we
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* don't. If we have kcmp() this will only return true for
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* dup()ed file descriptors, but not otherwise. If we don't
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* have kcmp() this will also return true for two fds of the same
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* file, created by separate open() calls. Since we use this
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* call mostly for filtering out duplicates in the fd store
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* this difference hopefully doesn't matter too much. */
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if (a == b)
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return true;
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/* Try to use kcmp() if we have it. */
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pid = getpid_cached();
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r = kcmp(pid, pid, KCMP_FILE, a, b);
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if (r == 0)
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return true;
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if (r > 0)
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return false;
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if (errno != ENOSYS)
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return -errno;
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/* We don't have kcmp(), use fstat() instead. */
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if (fstat(a, &sta) < 0)
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return -errno;
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if (fstat(b, &stb) < 0)
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return -errno;
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if ((sta.st_mode & S_IFMT) != (stb.st_mode & S_IFMT))
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return false;
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/* We consider all device fds different, since two device fds
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* might refer to quite different device contexts even though
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* they share the same inode and backing dev_t. */
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if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode))
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return false;
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if (sta.st_dev != stb.st_dev || sta.st_ino != stb.st_ino)
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return false;
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/* The fds refer to the same inode on disk, let's also check
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* if they have the same fd flags. This is useful to
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* distinguish the read and write side of a pipe created with
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* pipe(). */
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fa = fcntl(a, F_GETFL);
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if (fa < 0)
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return -errno;
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fb = fcntl(b, F_GETFL);
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if (fb < 0)
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return -errno;
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return fa == fb;
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}
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void cmsg_close_all(struct msghdr *mh) {
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struct cmsghdr *cmsg;
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assert(mh);
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CMSG_FOREACH(cmsg, mh)
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if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
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close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int));
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}
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bool fdname_is_valid(const char *s) {
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const char *p;
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/* Validates a name for $LISTEN_FDNAMES. We basically allow
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* everything ASCII that's not a control character. Also, as
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* special exception the ":" character is not allowed, as we
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* use that as field separator in $LISTEN_FDNAMES.
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*
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* Note that the empty string is explicitly allowed
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* here. However, we limit the length of the names to 255
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* characters. */
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if (!s)
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return false;
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for (p = s; *p; p++) {
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if (*p < ' ')
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return false;
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if (*p >= 127)
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return false;
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if (*p == ':')
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return false;
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}
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return p - s < 256;
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}
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int fd_get_path(int fd, char **ret) {
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char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
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int r;
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xsprintf(procfs_path, "/proc/self/fd/%i", fd);
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r = readlink_malloc(procfs_path, ret);
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if (r == -ENOENT) /* If the file doesn't exist the fd is invalid */
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return -EBADF;
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return r;
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}
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int move_fd(int from, int to, int cloexec) {
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int r;
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/* Move fd 'from' to 'to', make sure FD_CLOEXEC remains equal if requested, and release the old fd. If
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* 'cloexec' is passed as -1, the original FD_CLOEXEC is inherited for the new fd. If it is 0, it is turned
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* off, if it is > 0 it is turned on. */
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if (from < 0)
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return -EBADF;
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if (to < 0)
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return -EBADF;
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if (from == to) {
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if (cloexec >= 0) {
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r = fd_cloexec(to, cloexec);
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if (r < 0)
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return r;
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}
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return to;
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}
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if (cloexec < 0) {
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int fl;
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fl = fcntl(from, F_GETFD, 0);
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if (fl < 0)
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return -errno;
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cloexec = !!(fl & FD_CLOEXEC);
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}
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r = dup3(from, to, cloexec ? O_CLOEXEC : 0);
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if (r < 0)
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return -errno;
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assert(r == to);
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safe_close(from);
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return to;
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}
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int acquire_data_fd(const void *data, size_t size, unsigned flags) {
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char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
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_cleanup_close_pair_ int pipefds[2] = { -1, -1 };
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char pattern[] = "/dev/shm/data-fd-XXXXXX";
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_cleanup_close_ int fd = -1;
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int isz = 0, r;
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ssize_t n;
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off_t f;
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assert(data || size == 0);
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/* Acquire a read-only file descriptor that when read from returns the specified data. This is much more
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* complex than I wish it was. But here's why:
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*
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* a) First we try to use memfds. They are the best option, as we can seal them nicely to make them
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* read-only. Unfortunately they require kernel 3.17, and – at the time of writing – we still support 3.14.
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*
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* b) Then, we try classic pipes. They are the second best options, as we can close the writing side, retaining
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* a nicely read-only fd in the reading side. However, they are by default quite small, and unprivileged
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* clients can only bump their size to a system-wide limit, which might be quite low.
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*
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* c) Then, we try an O_TMPFILE file in /dev/shm (that dir is the only suitable one known to exist from
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* earliest boot on). To make it read-only we open the fd a second time with O_RDONLY via
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* /proc/self/<fd>. Unfortunately O_TMPFILE is not available on older kernels on tmpfs.
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*
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* d) Finally, we try creating a regular file in /dev/shm, which we then delete.
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*
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* It sucks a bit that depending on the situation we return very different objects here, but that's Linux I
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* figure. */
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if (size == 0 && ((flags & ACQUIRE_NO_DEV_NULL) == 0)) {
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/* As a special case, return /dev/null if we have been called for an empty data block */
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r = open("/dev/null", O_RDONLY|O_CLOEXEC|O_NOCTTY);
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if (r < 0)
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return -errno;
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return r;
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}
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if ((flags & ACQUIRE_NO_MEMFD) == 0) {
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fd = memfd_new("data-fd");
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if (fd < 0)
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goto try_pipe;
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n = write(fd, data, size);
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if (n < 0)
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return -errno;
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if ((size_t) n != size)
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return -EIO;
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f = lseek(fd, 0, SEEK_SET);
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if (f != 0)
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return -errno;
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r = memfd_set_sealed(fd);
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if (r < 0)
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return r;
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r = fd;
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fd = -1;
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return r;
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}
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try_pipe:
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if ((flags & ACQUIRE_NO_PIPE) == 0) {
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if (pipe2(pipefds, O_CLOEXEC|O_NONBLOCK) < 0)
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return -errno;
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isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
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if (isz < 0)
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return -errno;
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if ((size_t) isz < size) {
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isz = (int) size;
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if (isz < 0 || (size_t) isz != size)
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return -E2BIG;
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/* Try to bump the pipe size */
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(void) fcntl(pipefds[1], F_SETPIPE_SZ, isz);
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/* See if that worked */
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isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
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if (isz < 0)
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return -errno;
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if ((size_t) isz < size)
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goto try_dev_shm;
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}
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n = write(pipefds[1], data, size);
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if (n < 0)
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return -errno;
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if ((size_t) n != size)
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return -EIO;
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(void) fd_nonblock(pipefds[0], false);
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r = pipefds[0];
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pipefds[0] = -1;
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return r;
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}
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try_dev_shm:
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if ((flags & ACQUIRE_NO_TMPFILE) == 0) {
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fd = open("/dev/shm", O_RDWR|O_TMPFILE|O_CLOEXEC, 0500);
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if (fd < 0)
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goto try_dev_shm_without_o_tmpfile;
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n = write(fd, data, size);
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if (n < 0)
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return -errno;
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if ((size_t) n != size)
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return -EIO;
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/* Let's reopen the thing, in order to get an O_RDONLY fd for the original O_RDWR one */
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xsprintf(procfs_path, "/proc/self/fd/%i", fd);
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r = open(procfs_path, O_RDONLY|O_CLOEXEC);
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if (r < 0)
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return -errno;
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return r;
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}
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try_dev_shm_without_o_tmpfile:
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if ((flags & ACQUIRE_NO_REGULAR) == 0) {
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fd = mkostemp_safe(pattern);
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if (fd < 0)
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return fd;
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n = write(fd, data, size);
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if (n < 0) {
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r = -errno;
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goto unlink_and_return;
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}
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if ((size_t) n != size) {
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r = -EIO;
|
||
goto unlink_and_return;
|
||
}
|
||
|
||
/* Let's reopen the thing, in order to get an O_RDONLY fd for the original O_RDWR one */
|
||
r = open(pattern, O_RDONLY|O_CLOEXEC);
|
||
if (r < 0)
|
||
r = -errno;
|
||
|
||
unlink_and_return:
|
||
(void) unlink(pattern);
|
||
return r;
|
||
}
|
||
|
||
return -EOPNOTSUPP;
|
||
}
|
||
|
||
int fd_move_above_stdio(int fd) {
|
||
int flags, copy;
|
||
PROTECT_ERRNO;
|
||
|
||
/* Moves the specified file descriptor if possible out of the range [0…2], i.e. the range of
|
||
* stdin/stdout/stderr. If it can't be moved outside of this range the original file descriptor is
|
||
* returned. This call is supposed to be used for long-lasting file descriptors we allocate in our code that
|
||
* might get loaded into foreign code, and where we want ensure our fds are unlikely used accidentally as
|
||
* stdin/stdout/stderr of unrelated code.
|
||
*
|
||
* Note that this doesn't fix any real bugs, it just makes it less likely that our code will be affected by
|
||
* buggy code from others that mindlessly invokes 'fprintf(stderr, …' or similar in places where stderr has
|
||
* been closed before.
|
||
*
|
||
* This function is written in a "best-effort" and "least-impact" style. This means whenever we encounter an
|
||
* error we simply return the original file descriptor, and we do not touch errno. */
|
||
|
||
if (fd < 0 || fd > 2)
|
||
return fd;
|
||
|
||
flags = fcntl(fd, F_GETFD, 0);
|
||
if (flags < 0)
|
||
return fd;
|
||
|
||
if (flags & FD_CLOEXEC)
|
||
copy = fcntl(fd, F_DUPFD_CLOEXEC, 3);
|
||
else
|
||
copy = fcntl(fd, F_DUPFD, 3);
|
||
if (copy < 0)
|
||
return fd;
|
||
|
||
assert(copy > 2);
|
||
|
||
(void) close(fd);
|
||
return copy;
|
||
}
|
||
|
||
int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd) {
|
||
|
||
int fd[3] = { /* Put together an array of fds we work on */
|
||
original_input_fd,
|
||
original_output_fd,
|
||
original_error_fd
|
||
};
|
||
|
||
int r, i,
|
||
null_fd = -1, /* if we open /dev/null, we store the fd to it here */
|
||
copy_fd[3] = { -1, -1, -1 }; /* This contains all fds we duplicate here temporarily, and hence need to close at the end */
|
||
bool null_readable, null_writable;
|
||
|
||
/* Sets up stdin, stdout, stderr with the three file descriptors passed in. If any of the descriptors is
|
||
* specified as -1 it will be connected with /dev/null instead. If any of the file descriptors is passed as
|
||
* itself (e.g. stdin as STDIN_FILENO) it is left unmodified, but the O_CLOEXEC bit is turned off should it be
|
||
* on.
|
||
*
|
||
* Note that if any of the passed file descriptors are > 2 they will be closed — both on success and on
|
||
* failure! Thus, callers should assume that when this function returns the input fds are invalidated.
|
||
*
|
||
* Note that when this function fails stdin/stdout/stderr might remain half set up!
|
||
*
|
||
* O_CLOEXEC is turned off for all three file descriptors (which is how it should be for
|
||
* stdin/stdout/stderr). */
|
||
|
||
null_readable = original_input_fd < 0;
|
||
null_writable = original_output_fd < 0 || original_error_fd < 0;
|
||
|
||
/* First step, open /dev/null once, if we need it */
|
||
if (null_readable || null_writable) {
|
||
|
||
/* Let's open this with O_CLOEXEC first, and convert it to non-O_CLOEXEC when we move the fd to the final position. */
|
||
null_fd = open("/dev/null", (null_readable && null_writable ? O_RDWR :
|
||
null_readable ? O_RDONLY : O_WRONLY) | O_CLOEXEC);
|
||
if (null_fd < 0) {
|
||
r = -errno;
|
||
goto finish;
|
||
}
|
||
|
||
/* If this fd is in the 0…2 range, let's move it out of it */
|
||
if (null_fd < 3) {
|
||
int copy;
|
||
|
||
copy = fcntl(null_fd, F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
|
||
if (copy < 0) {
|
||
r = -errno;
|
||
goto finish;
|
||
}
|
||
|
||
safe_close(null_fd);
|
||
null_fd = copy;
|
||
}
|
||
}
|
||
|
||
/* Let's assemble fd[] with the fds to install in place of stdin/stdout/stderr */
|
||
for (i = 0; i < 3; i++) {
|
||
|
||
if (fd[i] < 0)
|
||
fd[i] = null_fd; /* A negative parameter means: connect this one to /dev/null */
|
||
else if (fd[i] != i && fd[i] < 3) {
|
||
/* This fd is in the 0…2 territory, but not at its intended place, move it out of there, so that we can work there. */
|
||
copy_fd[i] = fcntl(fd[i], F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */
|
||
if (copy_fd[i] < 0) {
|
||
r = -errno;
|
||
goto finish;
|
||
}
|
||
|
||
fd[i] = copy_fd[i];
|
||
}
|
||
}
|
||
|
||
/* At this point we now have the fds to use in fd[], and they are all above the stdio range, so that we
|
||
* have freedom to move them around. If the fds already were at the right places then the specific fds are
|
||
* -1. Let's now move them to the right places. This is the point of no return. */
|
||
for (i = 0; i < 3; i++) {
|
||
|
||
if (fd[i] == i) {
|
||
|
||
/* fd is already in place, but let's make sure O_CLOEXEC is off */
|
||
r = fd_cloexec(i, false);
|
||
if (r < 0)
|
||
goto finish;
|
||
|
||
} else {
|
||
assert(fd[i] > 2);
|
||
|
||
if (dup2(fd[i], i) < 0) { /* Turns off O_CLOEXEC on the new fd. */
|
||
r = -errno;
|
||
goto finish;
|
||
}
|
||
}
|
||
}
|
||
|
||
r = 0;
|
||
|
||
finish:
|
||
/* Close the original fds, but only if they were outside of the stdio range. Also, properly check for the same
|
||
* fd passed in multiple times. */
|
||
safe_close_above_stdio(original_input_fd);
|
||
if (original_output_fd != original_input_fd)
|
||
safe_close_above_stdio(original_output_fd);
|
||
if (original_error_fd != original_input_fd && original_error_fd != original_output_fd)
|
||
safe_close_above_stdio(original_error_fd);
|
||
|
||
/* Close the copies we moved > 2 */
|
||
for (i = 0; i < 3; i++)
|
||
safe_close(copy_fd[i]);
|
||
|
||
/* Close our null fd, if it's > 2 */
|
||
safe_close_above_stdio(null_fd);
|
||
|
||
return r;
|
||
}
|