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-rw-r--r--src/basic/fd-util.c967
1 files changed, 967 insertions, 0 deletions
diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
new file mode 100644
index 0000000..3e6ef5a
--- /dev/null
+++ b/src/basic/fd-util.c
@@ -0,0 +1,967 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/resource.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "copy.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "io-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"
+#include "tmpfile-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[static 2]) {
+ 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[], size_t n_fd) {
+ size_t 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[], size_t n_fdset) {
+ size_t i;
+
+ assert(n_fdset == 0 || fdset);
+
+ for (i = 0; i < n_fdset; i++)
+ if (fdset[i] == fd)
+ return true;
+
+ return false;
+}
+
+static int get_max_fd(void) {
+ struct rlimit rl;
+ rlim_t m;
+
+ /* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary
+ * and INT_MAX as upper boundary. */
+
+ if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
+ return -errno;
+
+ m = MAX(rl.rlim_cur, rl.rlim_max);
+ if (m < FD_SETSIZE) /* Let's always cover at least 1024 fds */
+ return FD_SETSIZE-1;
+
+ if (m == RLIM_INFINITY || m > INT_MAX) /* Saturate on overflow. After all fds are "int", hence can
+ * never be above INT_MAX */
+ return INT_MAX;
+
+ return (int) (m - 1);
+}
+
+int close_all_fds(const int except[], size_t 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, max_fd;
+
+ /* When /proc isn't available (for example in chroots) the fallback is brute forcing through
+ * the fd table */
+
+ max_fd = get_max_fd();
+ if (max_fd < 0)
+ return max_fd;
+
+ for (fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
+ 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 (!IN_SET(errno, ENOSYS, EACCES, EPERM))
+ 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;
+
+ return TAKE_FD(fd);
+ }
+
+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);
+
+ return TAKE_FD(pipefds[0]);
+ }
+
+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;
+}
+
+/* When the data is smaller or equal to 64K, try to place the copy in a memfd/pipe */
+#define DATA_FD_MEMORY_LIMIT (64U*1024U)
+
+/* If memfd/pipe didn't work out, then let's use a file in /tmp up to a size of 1M. If it's large than that use /var/tmp instead. */
+#define DATA_FD_TMP_LIMIT (1024U*1024U)
+
+int fd_duplicate_data_fd(int fd) {
+
+ _cleanup_close_ int copy_fd = -1, tmp_fd = -1;
+ _cleanup_free_ void *remains = NULL;
+ size_t remains_size = 0;
+ const char *td;
+ struct stat st;
+ int r;
+
+ /* Creates a 'data' fd from the specified source fd, containing all the same data in a read-only fashion, but
+ * independent of it (i.e. the source fd can be closed and unmounted after this call succeeded). Tries to be
+ * somewhat smart about where to place the data. In the best case uses a memfd(). If memfd() are not supported
+ * uses a pipe instead. For larger data will use an unlinked file in /tmp, and for even larger data one in
+ * /var/tmp. */
+
+ if (fstat(fd, &st) < 0)
+ return -errno;
+
+ /* For now, let's only accept regular files, sockets, pipes and char devices */
+ if (S_ISDIR(st.st_mode))
+ return -EISDIR;
+ if (S_ISLNK(st.st_mode))
+ return -ELOOP;
+ if (!S_ISREG(st.st_mode) && !S_ISSOCK(st.st_mode) && !S_ISFIFO(st.st_mode) && !S_ISCHR(st.st_mode))
+ return -EBADFD;
+
+ /* If we have reason to believe the data is bounded in size, then let's use memfds or pipes as backing fd. Note
+ * that we use the reported regular file size only as a hint, given that there are plenty special files in
+ * /proc and /sys which report a zero file size but can be read from. */
+
+ if (!S_ISREG(st.st_mode) || st.st_size < DATA_FD_MEMORY_LIMIT) {
+
+ /* Try a memfd first */
+ copy_fd = memfd_new("data-fd");
+ if (copy_fd >= 0) {
+ off_t f;
+
+ r = copy_bytes(fd, copy_fd, DATA_FD_MEMORY_LIMIT, 0);
+ if (r < 0)
+ return r;
+
+ f = lseek(copy_fd, 0, SEEK_SET);
+ if (f != 0)
+ return -errno;
+
+ if (r == 0) {
+ /* Did it fit into the limit? If so, we are done. */
+ r = memfd_set_sealed(copy_fd);
+ if (r < 0)
+ return r;
+
+ return TAKE_FD(copy_fd);
+ }
+
+ /* Hmm, pity, this didn't fit. Let's fall back to /tmp then, see below */
+
+ } else {
+ _cleanup_(close_pairp) int pipefds[2] = { -1, -1 };
+ int isz;
+
+ /* If memfds aren't available, use a pipe. Set O_NONBLOCK so that we will get EAGAIN rather
+ * then block indefinitely when we hit the pipe size limit */
+
+ if (pipe2(pipefds, O_CLOEXEC|O_NONBLOCK) < 0)
+ return -errno;
+
+ isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+ if (isz < 0)
+ return -errno;
+
+ /* Try to enlarge the pipe size if necessary */
+ if ((size_t) isz < DATA_FD_MEMORY_LIMIT) {
+
+ (void) fcntl(pipefds[1], F_SETPIPE_SZ, DATA_FD_MEMORY_LIMIT);
+
+ isz = fcntl(pipefds[1], F_GETPIPE_SZ, 0);
+ if (isz < 0)
+ return -errno;
+ }
+
+ if ((size_t) isz >= DATA_FD_MEMORY_LIMIT) {
+
+ r = copy_bytes_full(fd, pipefds[1], DATA_FD_MEMORY_LIMIT, 0, &remains, &remains_size, NULL, NULL);
+ if (r < 0 && r != -EAGAIN)
+ return r; /* If we get EAGAIN it could be because of the source or because of
+ * the destination fd, we can't know, as sendfile() and friends won't
+ * tell us. Hence, treat this as reason to fall back, just to be
+ * sure. */
+ if (r == 0) {
+ /* Everything fit in, yay! */
+ (void) fd_nonblock(pipefds[0], false);
+
+ return TAKE_FD(pipefds[0]);
+ }
+
+ /* Things didn't fit in. But we read data into the pipe, let's remember that, so that
+ * when writing the new file we incorporate this first. */
+ copy_fd = TAKE_FD(pipefds[0]);
+ }
+ }
+ }
+
+ /* If we have reason to believe this will fit fine in /tmp, then use that as first fallback. */
+ if ((!S_ISREG(st.st_mode) || st.st_size < DATA_FD_TMP_LIMIT) &&
+ (DATA_FD_MEMORY_LIMIT + remains_size) < DATA_FD_TMP_LIMIT) {
+ off_t f;
+
+ tmp_fd = open_tmpfile_unlinkable(NULL /* NULL as directory means /tmp */, O_RDWR|O_CLOEXEC);
+ if (tmp_fd < 0)
+ return tmp_fd;
+
+ if (copy_fd >= 0) {
+ /* If we tried a memfd/pipe first and it ended up being too large, then copy this into the
+ * temporary file first. */
+
+ r = copy_bytes(copy_fd, tmp_fd, UINT64_MAX, 0);
+ if (r < 0)
+ return r;
+
+ assert(r == 0);
+ }
+
+ if (remains_size > 0) {
+ /* If there were remaining bytes (i.e. read into memory, but not written out yet) from the
+ * failed copy operation, let's flush them out next. */
+
+ r = loop_write(tmp_fd, remains, remains_size, false);
+ if (r < 0)
+ return r;
+ }
+
+ r = copy_bytes(fd, tmp_fd, DATA_FD_TMP_LIMIT - DATA_FD_MEMORY_LIMIT - remains_size, COPY_REFLINK);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ goto finish; /* Yay, it fit in */
+
+ /* It didn't fit in. Let's not forget to use what we already used */
+ f = lseek(tmp_fd, 0, SEEK_SET);
+ if (f != 0)
+ return -errno;
+
+ safe_close(copy_fd);
+ copy_fd = TAKE_FD(tmp_fd);
+
+ remains = mfree(remains);
+ remains_size = 0;
+ }
+
+ /* As last fallback use /var/tmp */
+ r = var_tmp_dir(&td);
+ if (r < 0)
+ return r;
+
+ tmp_fd = open_tmpfile_unlinkable(td, O_RDWR|O_CLOEXEC);
+ if (tmp_fd < 0)
+ return tmp_fd;
+
+ if (copy_fd >= 0) {
+ /* If we tried a memfd/pipe first, or a file in /tmp, and it ended up being too large, than copy this
+ * into the temporary file first. */
+ r = copy_bytes(copy_fd, tmp_fd, UINT64_MAX, COPY_REFLINK);
+ if (r < 0)
+ return r;
+
+ assert(r == 0);
+ }
+
+ if (remains_size > 0) {
+ /* Then, copy in any read but not yet written bytes. */
+ r = loop_write(tmp_fd, remains, remains_size, false);
+ if (r < 0)
+ return r;
+ }
+
+ /* Copy in the rest */
+ r = copy_bytes(fd, tmp_fd, UINT64_MAX, COPY_REFLINK);
+ if (r < 0)
+ return r;
+
+ assert(r == 0);
+
+finish:
+ /* Now convert the O_RDWR file descriptor into an O_RDONLY one (and as side effect seek to the beginning of the
+ * file again */
+
+ return fd_reopen(tmp_fd, O_RDONLY|O_CLOEXEC);
+}
+
+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;
+}
+
+int read_nr_open(void) {
+ _cleanup_free_ char *nr_open = NULL;
+ int r;
+
+ /* Returns the kernel's current fd limit, either by reading it of /proc/sys if that works, or using the
+ * hard-coded default compiled-in value of current kernels (1M) if not. This call will never fail. */
+
+ r = read_one_line_file("/proc/sys/fs/nr_open", &nr_open);
+ if (r < 0)
+ log_debug_errno(r, "Failed to read /proc/sys/fs/nr_open, ignoring: %m");
+ else {
+ int v;
+
+ r = safe_atoi(nr_open, &v);
+ if (r < 0)
+ log_debug_errno(r, "Failed to parse /proc/sys/fs/nr_open value '%s', ignoring: %m", nr_open);
+ else
+ return v;
+ }
+
+ /* If we fail, fallback to the hard-coded kernel limit of 1024 * 1024. */
+ return 1024 * 1024;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 18:58:01 +0000