| /* SPDX-License-Identifier: LGPL-2.1+ */ |
| /*** |
| This file is part of systemd. |
| |
| Copyright 2010 Lennart Poettering |
| |
| systemd is free software; you can redistribute it and/or modify it |
| under the terms of the GNU Lesser General Public License as published by |
| the Free Software Foundation; either version 2.1 of the License, or |
| (at your option) any later version. |
| |
| systemd is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public License |
| along with systemd; If not, see <http://www.gnu.org/licenses/>. |
| ***/ |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <sys/resource.h> |
| #include <sys/socket.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| #include "dirent-util.h" |
| #include "fd-util.h" |
| #include "fileio.h" |
| #include "fs-util.h" |
| #include "macro.h" |
| #include "memfd-util.h" |
| #include "missing.h" |
| #include "parse-util.h" |
| #include "path-util.h" |
| #include "process-util.h" |
| #include "socket-util.h" |
| #include "stdio-util.h" |
| #include "util.h" |
| |
| int close_nointr(int fd) { |
| assert(fd >= 0); |
| |
| if (close(fd) >= 0) |
| return 0; |
| |
| /* |
| * Just ignore EINTR; a retry loop is the wrong thing to do on |
| * Linux. |
| * |
| * http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html |
| * https://bugzilla.gnome.org/show_bug.cgi?id=682819 |
| * http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR |
| * https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain |
| */ |
| if (errno == EINTR) |
| return 0; |
| |
| return -errno; |
| } |
| |
| int safe_close(int fd) { |
| |
| /* |
| * Like close_nointr() but cannot fail. Guarantees errno is |
| * unchanged. Is a NOP with negative fds passed, and returns |
| * -1, so that it can be used in this syntax: |
| * |
| * fd = safe_close(fd); |
| */ |
| |
| if (fd >= 0) { |
| PROTECT_ERRNO; |
| |
| /* The kernel might return pretty much any error code |
| * via close(), but the fd will be closed anyway. The |
| * only condition we want to check for here is whether |
| * the fd was invalid at all... */ |
| |
| assert_se(close_nointr(fd) != -EBADF); |
| } |
| |
| return -1; |
| } |
| |
| void safe_close_pair(int p[]) { |
| assert(p); |
| |
| if (p[0] == p[1]) { |
| /* Special case pairs which use the same fd in both |
| * directions... */ |
| p[0] = p[1] = safe_close(p[0]); |
| return; |
| } |
| |
| p[0] = safe_close(p[0]); |
| p[1] = safe_close(p[1]); |
| } |
| |
| void close_many(const int fds[], unsigned n_fd) { |
| unsigned i; |
| |
| assert(fds || n_fd <= 0); |
| |
| for (i = 0; i < n_fd; i++) |
| safe_close(fds[i]); |
| } |
| |
| int fclose_nointr(FILE *f) { |
| assert(f); |
| |
| /* Same as close_nointr(), but for fclose() */ |
| |
| if (fclose(f) == 0) |
| return 0; |
| |
| if (errno == EINTR) |
| return 0; |
| |
| return -errno; |
| } |
| |
| FILE* safe_fclose(FILE *f) { |
| |
| /* Same as safe_close(), but for fclose() */ |
| |
| if (f) { |
| PROTECT_ERRNO; |
| |
| assert_se(fclose_nointr(f) != EBADF); |
| } |
| |
| return NULL; |
| } |
| |
| DIR* safe_closedir(DIR *d) { |
| |
| if (d) { |
| PROTECT_ERRNO; |
| |
| assert_se(closedir(d) >= 0 || errno != EBADF); |
| } |
| |
| return NULL; |
| } |
| |
| int fd_nonblock(int fd, bool nonblock) { |
| int flags, nflags; |
| |
| assert(fd >= 0); |
| |
| flags = fcntl(fd, F_GETFL, 0); |
| if (flags < 0) |
| return -errno; |
| |
| if (nonblock) |
| nflags = flags | O_NONBLOCK; |
| else |
| nflags = flags & ~O_NONBLOCK; |
| |
| if (nflags == flags) |
| return 0; |
| |
| if (fcntl(fd, F_SETFL, nflags) < 0) |
| return -errno; |
| |
| return 0; |
| } |
| |
| int fd_cloexec(int fd, bool cloexec) { |
| int flags, nflags; |
| |
| assert(fd >= 0); |
| |
| flags = fcntl(fd, F_GETFD, 0); |
| if (flags < 0) |
| return -errno; |
| |
| if (cloexec) |
| nflags = flags | FD_CLOEXEC; |
| else |
| nflags = flags & ~FD_CLOEXEC; |
| |
| if (nflags == flags) |
| return 0; |
| |
| if (fcntl(fd, F_SETFD, nflags) < 0) |
| return -errno; |
| |
| return 0; |
| } |
| |
| _pure_ static bool fd_in_set(int fd, const int fdset[], unsigned n_fdset) { |
| unsigned i; |
| |
| assert(n_fdset == 0 || fdset); |
| |
| for (i = 0; i < n_fdset; i++) |
| if (fdset[i] == fd) |
| return true; |
| |
| return false; |
| } |
| |
| int close_all_fds(const int except[], unsigned n_except) { |
| _cleanup_closedir_ DIR *d = NULL; |
| struct dirent *de; |
| int r = 0; |
| |
| assert(n_except == 0 || except); |
| |
| d = opendir("/proc/self/fd"); |
| if (!d) { |
| int fd; |
| struct rlimit rl; |
| |
| /* When /proc isn't available (for example in chroots) |
| * the fallback is brute forcing through the fd |
| * table */ |
| |
| assert_se(getrlimit(RLIMIT_NOFILE, &rl) >= 0); |
| for (fd = 3; fd < (int) rl.rlim_max; fd ++) { |
| int q; |
| |
| if (fd_in_set(fd, except, n_except)) |
| continue; |
| |
| q = close_nointr(fd); |
| if (q < 0 && q != -EBADF && r >= 0) |
| r = q; |
| } |
| |
| return r; |
| } |
| |
| FOREACH_DIRENT(de, d, return -errno) { |
| int fd = -1, q; |
| |
| if (safe_atoi(de->d_name, &fd) < 0) |
| /* Let's better ignore this, just in case */ |
| continue; |
| |
| if (fd < 3) |
| continue; |
| |
| if (fd == dirfd(d)) |
| continue; |
| |
| if (fd_in_set(fd, except, n_except)) |
| continue; |
| |
| q = close_nointr(fd); |
| if (q < 0 && q != -EBADF && r >= 0) /* Valgrind has its own FD and doesn't want to have it closed */ |
| r = q; |
| } |
| |
| return r; |
| } |
| |
| int same_fd(int a, int b) { |
| struct stat sta, stb; |
| pid_t pid; |
| int r, fa, fb; |
| |
| assert(a >= 0); |
| assert(b >= 0); |
| |
| /* Compares two file descriptors. Note that semantics are |
| * quite different depending on whether we have kcmp() or we |
| * don't. If we have kcmp() this will only return true for |
| * dup()ed file descriptors, but not otherwise. If we don't |
| * have kcmp() this will also return true for two fds of the same |
| * file, created by separate open() calls. Since we use this |
| * call mostly for filtering out duplicates in the fd store |
| * this difference hopefully doesn't matter too much. */ |
| |
| if (a == b) |
| return true; |
| |
| /* Try to use kcmp() if we have it. */ |
| pid = getpid_cached(); |
| r = kcmp(pid, pid, KCMP_FILE, a, b); |
| if (r == 0) |
| return true; |
| if (r > 0) |
| return false; |
| if (errno != ENOSYS) |
| return -errno; |
| |
| /* We don't have kcmp(), use fstat() instead. */ |
| if (fstat(a, &sta) < 0) |
| return -errno; |
| |
| if (fstat(b, &stb) < 0) |
| return -errno; |
| |
| if ((sta.st_mode & S_IFMT) != (stb.st_mode & S_IFMT)) |
| return false; |
| |
| /* We consider all device fds different, since two device fds |
| * might refer to quite different device contexts even though |
| * they share the same inode and backing dev_t. */ |
| |
| if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode)) |
| return false; |
| |
| if (sta.st_dev != stb.st_dev || sta.st_ino != stb.st_ino) |
| return false; |
| |
| /* The fds refer to the same inode on disk, let's also check |
| * if they have the same fd flags. This is useful to |
| * distinguish the read and write side of a pipe created with |
| * pipe(). */ |
| fa = fcntl(a, F_GETFL); |
| if (fa < 0) |
| return -errno; |
| |
| fb = fcntl(b, F_GETFL); |
| if (fb < 0) |
| return -errno; |
| |
| return fa == fb; |
| } |
| |
| void cmsg_close_all(struct msghdr *mh) { |
| struct cmsghdr *cmsg; |
| |
| assert(mh); |
| |
| CMSG_FOREACH(cmsg, mh) |
| if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) |
| close_many((int*) CMSG_DATA(cmsg), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int)); |
| } |
| |
| bool fdname_is_valid(const char *s) { |
| const char *p; |
| |
| /* Validates a name for $LISTEN_FDNAMES. We basically allow |
| * everything ASCII that's not a control character. Also, as |
| * special exception the ":" character is not allowed, as we |
| * use that as field separator in $LISTEN_FDNAMES. |
| * |
| * Note that the empty string is explicitly allowed |
| * here. However, we limit the length of the names to 255 |
| * characters. */ |
| |
| if (!s) |
| return false; |
| |
| for (p = s; *p; p++) { |
| if (*p < ' ') |
| return false; |
| if (*p >= 127) |
| return false; |
| if (*p == ':') |
| return false; |
| } |
| |
| return p - s < 256; |
| } |
| |
| int fd_get_path(int fd, char **ret) { |
| char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; |
| int r; |
| |
| xsprintf(procfs_path, "/proc/self/fd/%i", fd); |
| r = readlink_malloc(procfs_path, ret); |
| if (r == -ENOENT) { |
| /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's make |
| * things debuggable and distuingish the two. */ |
| |
| if (access("/proc/self/fd/", F_OK) < 0) |
| /* /proc is not available or not set up properly, we're most likely in some chroot |
| * environment. */ |
| return errno == ENOENT ? -EOPNOTSUPP : -errno; |
| |
| return -EBADF; /* The directory exists, hence it's the fd that doesn't. */ |
| } |
| |
| return r; |
| } |
| |
| int move_fd(int from, int to, int cloexec) { |
| int r; |
| |
| /* Move fd 'from' to 'to', make sure FD_CLOEXEC remains equal if requested, and release the old fd. If |
| * 'cloexec' is passed as -1, the original FD_CLOEXEC is inherited for the new fd. If it is 0, it is turned |
| * off, if it is > 0 it is turned on. */ |
| |
| if (from < 0) |
| return -EBADF; |
| if (to < 0) |
| return -EBADF; |
| |
| if (from == to) { |
| |
| if (cloexec >= 0) { |
| r = fd_cloexec(to, cloexec); |
| if (r < 0) |
| return r; |
| } |
| |
| return to; |
| } |
| |
| if (cloexec < 0) { |
| int fl; |
| |
| fl = fcntl(from, F_GETFD, 0); |
| if (fl < 0) |
| return -errno; |
| |
| cloexec = !!(fl & FD_CLOEXEC); |
| } |
| |
| r = dup3(from, to, cloexec ? O_CLOEXEC : 0); |
| if (r < 0) |
| return -errno; |
| |
| assert(r == to); |
| |
| safe_close(from); |
| |
| return to; |
| } |
| |
| int acquire_data_fd(const void *data, size_t size, unsigned flags) { |
| |
| _cleanup_close_pair_ int pipefds[2] = { -1, -1 }; |
| char pattern[] = "/dev/shm/data-fd-XXXXXX"; |
| _cleanup_close_ int fd = -1; |
| int isz = 0, r; |
| ssize_t n; |
| off_t f; |
| |
| assert(data || size == 0); |
| |
| /* Acquire a read-only file descriptor that when read from returns the specified data. This is much more |
| * complex than I wish it was. But here's why: |
| * |
| * a) First we try to use memfds. They are the best option, as we can seal them nicely to make them |
| * read-only. Unfortunately they require kernel 3.17, and – at the time of writing – we still support 3.14. |
| * |
| * b) Then, we try classic pipes. They are the second best options, as we can close the writing side, retaining |
| * a nicely read-only fd in the reading side. However, they are by default quite small, and unprivileged |
| * clients can only bump their size to a system-wide limit, which might be quite low. |
| * |
| * c) Then, we try an O_TMPFILE file in /dev/shm (that dir is the only suitable one known to exist from |
| * earliest boot on). To make it read-only we open the fd a second time with O_RDONLY via |
| * /proc/self/<fd>. Unfortunately O_TMPFILE is not available on older kernels on tmpfs. |
| * |
| * d) Finally, we try creating a regular file in /dev/shm, which we then delete. |
| * |
| * It sucks a bit that depending on the situation we return very different objects here, but that's Linux I |
| * figure. */ |
| |
| if (size == 0 && ((flags & ACQUIRE_NO_DEV_NULL) == 0)) { |
| /* As a special case, return /dev/null if we have been called for an empty data block */ |
| r = open("/dev/null", O_RDONLY|O_CLOEXEC|O_NOCTTY); |
| if (r < 0) |
| return -errno; |
| |
| return r; |
| } |
| |
| if ((flags & ACQUIRE_NO_MEMFD) == 0) { |
| fd = memfd_new("data-fd"); |
| if (fd < 0) |
| goto try_pipe; |
| |
| n = write(fd, data, size); |
| if (n < 0) |
| return -errno; |
| if ((size_t) n != size) |
| return -EIO; |
| |
| f = lseek(fd, 0, SEEK_SET); |
| if (f != 0) |
| return -errno; |
| |
| r = memfd_set_sealed(fd); |
| if (r < 0) |
| return r; |
| |
| r = fd; |
| fd = -1; |
| |
| return r; |
| } |
| |
| try_pipe: |
| if ((flags & ACQUIRE_NO_PIPE) == 0) { |
| if (pipe2(pipefds, O_CLOEXEC|O_NONBLOCK) < 0) |
| return -errno; |
| |
| isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0); |
| if (isz < 0) |
| return -errno; |
| |
| if ((size_t) isz < size) { |
| isz = (int) size; |
| if (isz < 0 || (size_t) isz != size) |
| return -E2BIG; |
| |
| /* Try to bump the pipe size */ |
| (void) fcntl(pipefds[1], F_SETPIPE_SZ, isz); |
| |
| /* See if that worked */ |
| isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0); |
| if (isz < 0) |
| return -errno; |
| |
| if ((size_t) isz < size) |
| goto try_dev_shm; |
| } |
| |
| n = write(pipefds[1], data, size); |
| if (n < 0) |
| return -errno; |
| if ((size_t) n != size) |
| return -EIO; |
| |
| (void) fd_nonblock(pipefds[0], false); |
| |
| r = pipefds[0]; |
| pipefds[0] = -1; |
| |
| return r; |
| } |
| |
| try_dev_shm: |
| if ((flags & ACQUIRE_NO_TMPFILE) == 0) { |
| fd = open("/dev/shm", O_RDWR|O_TMPFILE|O_CLOEXEC, 0500); |
| if (fd < 0) |
| goto try_dev_shm_without_o_tmpfile; |
| |
| n = write(fd, data, size); |
| if (n < 0) |
| return -errno; |
| if ((size_t) n != size) |
| return -EIO; |
| |
| /* Let's reopen the thing, in order to get an O_RDONLY fd for the original O_RDWR one */ |
| return fd_reopen(fd, O_RDONLY|O_CLOEXEC); |
| } |
| |
| try_dev_shm_without_o_tmpfile: |
| if ((flags & ACQUIRE_NO_REGULAR) == 0) { |
| fd = mkostemp_safe(pattern); |
| if (fd < 0) |
| return fd; |
| |
| n = write(fd, data, size); |
| if (n < 0) { |
| r = -errno; |
| goto unlink_and_return; |
| } |
| if ((size_t) n != size) { |
| 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; |
| } |
| |
| int fd_reopen(int fd, int flags) { |
| char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; |
| int new_fd; |
| |
| /* Reopens the specified fd with new flags. This is useful for convert an O_PATH fd into a regular one, or to |
| * turn O_RDWR fds into O_RDONLY fds. |
| * |
| * This doesn't work on sockets (since they cannot be open()ed, ever). |
| * |
| * This implicitly resets the file read index to 0. */ |
| |
| xsprintf(procfs_path, "/proc/self/fd/%i", fd); |
| new_fd = open(procfs_path, flags); |
| if (new_fd < 0) |
| return -errno; |
| |
| return new_fd; |
| } |