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https://github.com/morgan9e/systemd
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4424e6c811
struct statx in glibc header was introduced in glibc-2.28 (fd70af45528d59a00eb3190ef6706cb299488fcd), but at that time, sys/stat.h conflicts with linux/stat.h. Since glibc-2.30 (5dad6ffbb2b76215cfcd38c3001778536ada8e8a), sys/stat.h includes linux/stat.h if exists. Since now our baseline of glibc is 2.31. Hence, we can drop workarounds for struct statx by importing linux/stat.h from newer kernel (v6.14-rc4).
840 lines
33 KiB
C
840 lines
33 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/mount.h>
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#if WANT_LINUX_FS_H
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#include <linux/fs.h>
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#endif
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#include "alloc-util.h"
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#include "chase.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "filesystems.h"
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#include "fs-util.h"
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#include "missing_fcntl.h"
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#include "missing_fs.h"
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#include "missing_mount.h"
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#include "missing_syscall.h"
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#include "mkdir.h"
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#include "mountpoint-util.h"
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#include "nulstr-util.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "stat-util.h"
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#include "stdio-util.h"
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#include "strv.h"
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#include "user-util.h"
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/* This is the original MAX_HANDLE_SZ definition from the kernel, when the API was introduced. We use that in place of
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* any more currently defined value to future-proof things: if the size is increased in the API headers, and our code
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* is recompiled then it would cease working on old kernels, as those refuse any sizes larger than this value with
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* EINVAL right-away. Hence, let's disconnect ourselves from any such API changes, and stick to the original definition
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* from when it was introduced. We use it as a start value only anyway (see below), and hence should be able to deal
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* with large file handles anyway. */
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#define ORIGINAL_MAX_HANDLE_SZ 128
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bool is_name_to_handle_at_fatal_error(int err) {
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/* name_to_handle_at() can return "acceptable" errors that are due to the context. For example
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* the file system does not support name_to_handle_at() (EOPNOTSUPP), or the syscall was blocked
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* (EACCES/EPERM; maybe through seccomp, because we are running inside of a container), or
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* the mount point is not triggered yet (EOVERFLOW, think autofs+nfs4), or some general name_to_handle_at()
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* flakiness (EINVAL). However other errors are not supposed to happen and therefore are considered
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* fatal ones. */
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assert(err < 0);
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if (ERRNO_IS_NEG_NOT_SUPPORTED(err))
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return false;
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if (ERRNO_IS_NEG_PRIVILEGE(err))
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return false;
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return !IN_SET(err, -EOVERFLOW, -EINVAL);
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}
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int name_to_handle_at_loop(
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int fd,
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const char *path,
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struct file_handle **ret_handle,
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int *ret_mnt_id,
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int flags) {
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size_t n = ORIGINAL_MAX_HANDLE_SZ;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH|AT_HANDLE_FID)) == 0);
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/* We need to invoke name_to_handle_at() in a loop, given that it might return EOVERFLOW when the specified
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* buffer is too small. Note that in contrast to what the docs might suggest, MAX_HANDLE_SZ is only good as a
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* start value, it is not an upper bound on the buffer size required.
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*
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* This improves on raw name_to_handle_at() also in one other regard: ret_handle and ret_mnt_id can be passed
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* as NULL if there's no interest in either. */
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for (;;) {
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_cleanup_free_ struct file_handle *h = NULL;
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int mnt_id = -1;
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h = malloc0(offsetof(struct file_handle, f_handle) + n);
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if (!h)
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return -ENOMEM;
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h->handle_bytes = n;
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if (name_to_handle_at(fd, strempty(path), h, &mnt_id, flags) >= 0) {
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if (ret_handle)
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*ret_handle = TAKE_PTR(h);
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if (ret_mnt_id)
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*ret_mnt_id = mnt_id;
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return 0;
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}
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if (errno != EOVERFLOW)
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return -errno;
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if (!ret_handle && ret_mnt_id && mnt_id >= 0) {
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/* As it appears, name_to_handle_at() fills in mnt_id even when it returns EOVERFLOW when the
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* buffer is too small, but that's undocumented. Hence, let's make use of this if it appears to
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* be filled in, and the caller was interested in only the mount ID an nothing else. */
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*ret_mnt_id = mnt_id;
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return 0;
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}
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/* If name_to_handle_at() didn't increase the byte size, then this EOVERFLOW is caused by
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* something else (apparently EOVERFLOW is returned for untriggered nfs4 autofs mounts
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* sometimes), not by the too small buffer. In that case propagate EOVERFLOW */
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if (h->handle_bytes <= n)
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return -EOVERFLOW;
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/* The buffer was too small. Size the new buffer by what name_to_handle_at() returned. */
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n = h->handle_bytes;
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/* paranoia: check for overflow (note that .handle_bytes is unsigned only) */
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if (n > UINT_MAX - offsetof(struct file_handle, f_handle))
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return -EOVERFLOW;
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}
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}
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int name_to_handle_at_try_fid(
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int fd,
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const char *path,
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struct file_handle **ret_handle,
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int *ret_mnt_id,
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int flags) {
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int r;
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assert(fd >= 0 || fd == AT_FDCWD);
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/* First issues name_to_handle_at() with AT_HANDLE_FID. If this fails and this is not a fatal error
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* we'll try without the flag, in order to support older kernels that didn't have AT_HANDLE_FID
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* (i.e. older than Linux 6.5). */
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r = name_to_handle_at_loop(fd, path, ret_handle, ret_mnt_id, flags | AT_HANDLE_FID);
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if (r >= 0 || is_name_to_handle_at_fatal_error(r))
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return r;
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return name_to_handle_at_loop(fd, path, ret_handle, ret_mnt_id, flags & ~AT_HANDLE_FID);
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}
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static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *ret_mnt_id) {
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char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
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_cleanup_free_ char *fdinfo = NULL;
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_cleanup_close_ int subfd = -EBADF;
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int r;
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
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assert(ret_mnt_id);
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if ((flags & AT_EMPTY_PATH) && isempty(filename))
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xsprintf(path, "/proc/self/fdinfo/%i", fd);
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else {
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subfd = openat(fd, filename, O_CLOEXEC|O_PATH|(flags & AT_SYMLINK_FOLLOW ? 0 : O_NOFOLLOW));
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if (subfd < 0)
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return -errno;
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xsprintf(path, "/proc/self/fdinfo/%i", subfd);
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}
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r = read_full_virtual_file(path, &fdinfo, NULL);
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if (r == -ENOENT)
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return proc_fd_enoent_errno();
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if (r < 0)
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return r;
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char *p = find_line_startswith(fdinfo, "mnt_id:");
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if (!p)
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return -EBADMSG;
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p = skip_leading_chars(p, /* bad = */ NULL);
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p[strcspn(p, WHITESPACE)] = 0;
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return safe_atoi(p, ret_mnt_id);
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}
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static bool filename_possibly_with_slash_suffix(const char *s) {
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const char *slash, *copied;
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/* Checks whether the specified string is either file name, or a filename with a suffix of
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* slashes. But nothing else.
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*
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* this is OK: foo, bar, foo/, bar/, foo//, bar///
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* this is not OK: "", "/", "/foo", "foo/bar", ".", ".." … */
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slash = strchr(s, '/');
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if (!slash)
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return filename_is_valid(s);
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if (slash - s > PATH_MAX) /* We want to allocate on the stack below, hence do a size check first */
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return false;
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if (slash[strspn(slash, "/")] != 0) /* Check that the suffix consist only of one or more slashes */
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return false;
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copied = strndupa_safe(s, slash - s);
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return filename_is_valid(copied);
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}
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bool file_handle_equal(const struct file_handle *a, const struct file_handle *b) {
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if (a == b)
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return true;
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if (!a != !b)
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return false;
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if (a->handle_type != b->handle_type)
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return false;
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return memcmp_nn(a->f_handle, a->handle_bytes, b->f_handle, b->handle_bytes) == 0;
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}
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int is_mount_point_at(int fd, const char *filename, int flags) {
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bool fd_is_self;
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int r;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert((flags & ~AT_SYMLINK_FOLLOW) == 0);
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if (isempty(filename)) {
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if (fd == AT_FDCWD)
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filename = ".";
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else {
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/* If the file name is empty we'll see if the specified 'fd' is a mount point.
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* That's only supported if the kernel supports statx(), or if the inode specified
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* via 'fd' refers to a directory. Otherwise, we'll have to fail (ENOTDIR), because
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* we have no kernel API to query the information we need. */
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flags |= AT_EMPTY_PATH;
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filename = "";
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}
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fd_is_self = true;
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} else if (STR_IN_SET(filename, ".", "./"))
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fd_is_self = true;
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else {
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/* Insist that the specified filename is actually a filename, and not a path, i.e. some inode
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* further up or down the tree then immediately below the specified directory fd. */
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if (!filename_possibly_with_slash_suffix(filename))
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return -EINVAL;
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fd_is_self = false;
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}
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/* First we will try statx()' STATX_ATTR_MOUNT_ROOT attribute, which is our ideal API, available
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* since kernel 5.8.
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*
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* If that fails, our second try is the name_to_handle_at() syscall, which tells us the mount id and
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* an opaque file "handle". It is not supported everywhere though (kernel compile-time option, not
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* all file systems are hooked up). If it works the mount id is usually good enough to tell us
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* whether something is a mount point.
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*
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* If that didn't work we will try to read the mount id from /proc/self/fdinfo/<fd>. This is almost
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* as good as name_to_handle_at(), however, does not return the opaque file handle. The opaque file
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* handle is pretty useful to detect the root directory, which we should always consider a mount
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* point. Hence we use this only as fallback.
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*
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* Note that traditionally the check is done via fstat()-based st_dev comparisons. However, various
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* file systems don't guarantee same st_dev across single fs anymore, e.g. unionfs exposes file systems
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* with a variety of st_dev reported. Also, btrfs subvolumes have different st_dev, even though
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* they aren't real mounts of their own. */
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struct statx sx = {}; /* explicitly initialize the struct to make msan silent. */
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if (statx(fd, filename,
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at_flags_normalize_nofollow(flags) |
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AT_NO_AUTOMOUNT | /* don't trigger automounts – mounts are a local concept, hence no need to trigger automounts to determine STATX_ATTR_MOUNT_ROOT */
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AT_STATX_DONT_SYNC, /* don't go to the network for this – for similar reasons */
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STATX_TYPE,
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&sx) < 0) {
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if (!ERRNO_IS_NOT_SUPPORTED(errno) && /* statx() is not supported by the kernel. */
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!ERRNO_IS_PRIVILEGE(errno) && /* maybe filtered by seccomp. */
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errno != EINVAL) /* glibc's fallback method returns EINVAL when AT_STATX_DONT_SYNC is set. */
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return -errno;
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/* If statx() is not available or forbidden, fall back to name_to_handle_at() below */
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} else if (FLAGS_SET(sx.stx_attributes_mask, STATX_ATTR_MOUNT_ROOT)) /* yay! */
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return FLAGS_SET(sx.stx_attributes, STATX_ATTR_MOUNT_ROOT);
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_cleanup_free_ struct file_handle *h = NULL, *h_parent = NULL;
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int mount_id = -1, mount_id_parent = -1;
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bool nosupp = false;
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r = name_to_handle_at_try_fid(fd, filename, &h, &mount_id, flags);
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if (r < 0) {
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if (is_name_to_handle_at_fatal_error(r))
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return r;
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if (!ERRNO_IS_NOT_SUPPORTED(r))
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goto fallback_fdinfo;
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/* This file system does not support name_to_handle_at(), hence let's see if the upper fs
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* supports it (in which case it is a mount point), otherwise fall back to the fdinfo logic. */
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nosupp = true;
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}
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if (fd_is_self)
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r = name_to_handle_at_try_fid(fd, "..", &h_parent, &mount_id_parent, 0); /* can't work for non-directories 😢 */
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else
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r = name_to_handle_at_try_fid(fd, "", &h_parent, &mount_id_parent, AT_EMPTY_PATH);
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if (r < 0) {
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if (is_name_to_handle_at_fatal_error(r))
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return r;
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if (!ERRNO_IS_NOT_SUPPORTED(r))
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goto fallback_fdinfo;
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if (nosupp)
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/* Both the parent and the directory can't do name_to_handle_at() */
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goto fallback_fdinfo;
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/* The parent can't do name_to_handle_at() but the directory we are
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* interested in can? If so, it must be a mount point. */
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return 1;
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}
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/* The parent can do name_to_handle_at() but the directory we are interested in can't? If
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* so, it must be a mount point. */
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if (nosupp)
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return 1;
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/* If the file handle for the directory we are interested in and its parent are identical,
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* we assume this is the root directory, which is a mount point. */
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if (file_handle_equal(h_parent, h))
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return 1;
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return mount_id != mount_id_parent;
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fallback_fdinfo:
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r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
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if (r < 0)
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return r;
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if (fd_is_self)
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r = fd_fdinfo_mnt_id(fd, "..", 0, &mount_id_parent); /* can't work for non-directories 😢 */
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else
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r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
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if (r < 0)
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return r;
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if (mount_id != mount_id_parent)
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return 1;
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/* Hmm, so, the mount ids are the same. This leaves one special case though for the root file
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* system. For that, let's see if the parent directory has the same inode as we are interested
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* in. */
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struct stat a, b;
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/* yay for fstatat() taking a different set of flags than the other _at() above */
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if (fstatat(fd, filename, &a, at_flags_normalize_nofollow(flags)) < 0)
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return -errno;
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if (fd_is_self)
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r = fstatat(fd, "..", &b, 0);
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else
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r = fstatat(fd, "", &b, AT_EMPTY_PATH);
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if (r < 0)
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return -errno;
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/* A directory with same device and inode as its parent must be the root directory. Otherwise
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* not a mount point.
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*
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* NB: we avoid inode_same_at() here because it internally attempts name_to_handle_at_try_fid() first,
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* which is redundant. */
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return stat_inode_same(&a, &b);
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}
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/* flags can be AT_SYMLINK_FOLLOW or 0 */
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int path_is_mount_point_full(const char *path, const char *root, int flags) {
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_cleanup_close_ int dfd = -EBADF;
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_cleanup_free_ char *fn = NULL;
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assert(path);
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assert((flags & ~AT_SYMLINK_FOLLOW) == 0);
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if (path_equal(path, "/"))
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return 1;
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/* we need to resolve symlinks manually, we can't just rely on is_mount_point_at() to do that for us;
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* if we have a structure like /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
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* look at needs to be /usr, not /. */
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dfd = chase_and_open_parent(path, root,
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CHASE_TRAIL_SLASH|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : CHASE_NOFOLLOW),
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&fn);
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if (dfd < 0)
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return dfd;
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return is_mount_point_at(dfd, fn, flags);
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}
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int path_get_mnt_id_at_fallback(int dir_fd, const char *path, int *ret) {
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int r;
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assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
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assert(ret);
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r = name_to_handle_at_loop(dir_fd, path, NULL, ret, isempty(path) ? AT_EMPTY_PATH : 0);
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if (r >= 0 || is_name_to_handle_at_fatal_error(r))
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return r;
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return fd_fdinfo_mnt_id(dir_fd, path, isempty(path) ? AT_EMPTY_PATH : 0, ret);
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}
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int path_get_mnt_id_at(int dir_fd, const char *path, int *ret) {
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struct statx sx;
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assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
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assert(ret);
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if (statx(dir_fd,
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strempty(path),
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(isempty(path) ? AT_EMPTY_PATH : AT_SYMLINK_NOFOLLOW) |
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AT_NO_AUTOMOUNT | /* don't trigger automounts, mnt_id is a local concept */
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AT_STATX_DONT_SYNC, /* don't go to the network, mnt_id is a local concept */
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STATX_MNT_ID,
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&sx) < 0) {
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if (!ERRNO_IS_NOT_SUPPORTED(errno) && /* statx() is not supported by the kernel. */
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!ERRNO_IS_PRIVILEGE(errno) && /* maybe filtered by seccomp. */
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errno != EINVAL) /* glibc's fallback method returns EINVAL when AT_STATX_DONT_SYNC is set. */
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return -errno;
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/* Fall back to name_to_handle_at() and then fdinfo if statx is not supported or we lack
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* privileges */
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} else if (FLAGS_SET(sx.stx_mask, STATX_MNT_ID)) {
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*ret = sx.stx_mnt_id;
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return 0;
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}
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return path_get_mnt_id_at_fallback(dir_fd, path, ret);
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}
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bool fstype_is_network(const char *fstype) {
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const char *x;
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x = startswith(fstype, "fuse.");
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if (x)
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fstype = x;
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|
||
if (nulstr_contains(filesystem_sets[FILESYSTEM_SET_NETWORK].value, fstype))
|
||
return true;
|
||
|
||
/* Filesystems not present in the internal database */
|
||
return STR_IN_SET(fstype,
|
||
"davfs",
|
||
"glusterfs",
|
||
"lustre",
|
||
"sshfs");
|
||
}
|
||
|
||
bool fstype_needs_quota(const char *fstype) {
|
||
/* 1. quotacheck needs to be run for some filesystems after they are mounted
|
||
* if the filesystem was not unmounted cleanly.
|
||
* 2. You may need to run quotaon to enable quota usage tracking and/or
|
||
* enforcement.
|
||
* ext2 - needs 1) and 2)
|
||
* ext3 - needs 2) if configured using usrjquota/grpjquota mount options
|
||
* ext4 - needs 1) if created without journal, needs 2) if created without QUOTA
|
||
* filesystem feature
|
||
* reiserfs - needs 2).
|
||
* jfs - needs 2)
|
||
* f2fs - needs 2) if configured using usrjquota/grpjquota/prjjquota mount options
|
||
* xfs - nothing needed
|
||
* gfs2 - nothing needed
|
||
* ocfs2 - nothing needed
|
||
* btrfs - nothing needed
|
||
* for reference see filesystem and quota manpages */
|
||
return STR_IN_SET(fstype,
|
||
"ext2",
|
||
"ext3",
|
||
"ext4",
|
||
"reiserfs",
|
||
"jfs",
|
||
"f2fs");
|
||
}
|
||
|
||
bool fstype_is_api_vfs(const char *fstype) {
|
||
assert(fstype);
|
||
|
||
const FilesystemSet *fs;
|
||
FOREACH_ARGUMENT(fs,
|
||
filesystem_sets + FILESYSTEM_SET_BASIC_API,
|
||
filesystem_sets + FILESYSTEM_SET_AUXILIARY_API,
|
||
filesystem_sets + FILESYSTEM_SET_PRIVILEGED_API,
|
||
filesystem_sets + FILESYSTEM_SET_TEMPORARY)
|
||
if (nulstr_contains(fs->value, fstype))
|
||
return true;
|
||
|
||
/* Filesystems not present in the internal database */
|
||
return STR_IN_SET(fstype,
|
||
"autofs",
|
||
"cpuset",
|
||
"devtmpfs");
|
||
}
|
||
|
||
bool fstype_is_blockdev_backed(const char *fstype) {
|
||
const char *x;
|
||
|
||
x = startswith(fstype, "fuse.");
|
||
if (x)
|
||
fstype = x;
|
||
|
||
return !streq(fstype, "9p") && !fstype_is_network(fstype) && !fstype_is_api_vfs(fstype);
|
||
}
|
||
|
||
bool fstype_is_ro(const char *fstype) {
|
||
/* All Linux file systems that are necessarily read-only */
|
||
return STR_IN_SET(fstype,
|
||
"DM_verity_hash",
|
||
"cramfs",
|
||
"erofs",
|
||
"iso9660",
|
||
"squashfs");
|
||
}
|
||
|
||
bool fstype_can_discard(const char *fstype) {
|
||
assert(fstype);
|
||
|
||
/* Use a curated list as first check, to avoid calling fsopen() which might load kmods, which might
|
||
* not be allowed in our MAC context. */
|
||
if (STR_IN_SET(fstype, "btrfs", "f2fs", "ext4", "vfat", "xfs"))
|
||
return true;
|
||
|
||
/* On new kernels we can just ask the kernel */
|
||
return mount_option_supported(fstype, "discard", NULL) > 0;
|
||
}
|
||
|
||
const char* fstype_norecovery_option(const char *fstype) {
|
||
int r;
|
||
|
||
assert(fstype);
|
||
|
||
/* Use a curated list as first check, to avoid calling fsopen() which might load kmods, which might
|
||
* not be allowed in our MAC context. */
|
||
if (STR_IN_SET(fstype, "ext3", "ext4", "xfs"))
|
||
return "norecovery";
|
||
|
||
/* btrfs dropped support for the "norecovery" option in 6.8
|
||
* (https://github.com/torvalds/linux/commit/a1912f712188291f9d7d434fba155461f1ebef66) and replaced
|
||
* it with rescue=nologreplay, so we check for the new name first and fall back to checking for the
|
||
* old name if the new name doesn't work. */
|
||
if (streq(fstype, "btrfs")) {
|
||
r = mount_option_supported(fstype, "rescue=nologreplay", NULL);
|
||
if (r == -EAGAIN) {
|
||
log_debug_errno(r, "Failed to check for btrfs 'rescue=nologreplay' option, assuming old kernel with 'norecovery': %m");
|
||
return "norecovery";
|
||
}
|
||
if (r < 0)
|
||
log_debug_errno(r, "Failed to check for btrfs 'rescue=nologreplay' option, assuming it is not supported: %m");
|
||
if (r > 0)
|
||
return "rescue=nologreplay";
|
||
}
|
||
|
||
/* On new kernels we can just ask the kernel */
|
||
return mount_option_supported(fstype, "norecovery", NULL) > 0 ? "norecovery" : NULL;
|
||
}
|
||
|
||
bool fstype_can_fmask_dmask(const char *fstype) {
|
||
assert(fstype);
|
||
|
||
/* Use a curated list as first check, to avoid calling fsopen() which might load kmods, which might
|
||
* not be allowed in our MAC context. If we don't know ourselves, on new kernels we can just ask the
|
||
* kernel. */
|
||
return streq(fstype, "vfat") || (mount_option_supported(fstype, "fmask", "0177") > 0 && mount_option_supported(fstype, "dmask", "0077") > 0);
|
||
}
|
||
|
||
bool fstype_can_uid_gid(const char *fstype) {
|
||
/* All file systems that have a uid=/gid= mount option that fixates the owners of all files and
|
||
* directories, current and future. Note that this does *not* ask the kernel via
|
||
* mount_option_supported() here because the uid=/gid= setting of various file systems mean different
|
||
* things: some apply it only to the root dir inode, others to all inodes in the file system. Thus we
|
||
* maintain the curated list below. 😢 */
|
||
|
||
return STR_IN_SET(fstype,
|
||
"adfs",
|
||
"exfat",
|
||
"fat",
|
||
"hfs",
|
||
"hpfs",
|
||
"iso9660",
|
||
"msdos",
|
||
"ntfs",
|
||
"vfat");
|
||
}
|
||
|
||
int dev_is_devtmpfs(void) {
|
||
_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
|
||
int mount_id, r;
|
||
char *e;
|
||
|
||
r = path_get_mnt_id("/dev", &mount_id);
|
||
if (r < 0)
|
||
return r;
|
||
|
||
r = fopen_unlocked("/proc/self/mountinfo", "re", &proc_self_mountinfo);
|
||
if (r == -ENOENT)
|
||
return proc_mounted() > 0 ? -ENOENT : -ENOSYS;
|
||
if (r < 0)
|
||
return r;
|
||
|
||
for (;;) {
|
||
_cleanup_free_ char *line = NULL;
|
||
int mid;
|
||
|
||
r = read_line(proc_self_mountinfo, LONG_LINE_MAX, &line);
|
||
if (r < 0)
|
||
return r;
|
||
if (r == 0)
|
||
break;
|
||
|
||
if (sscanf(line, "%i", &mid) != 1)
|
||
continue;
|
||
|
||
if (mid != mount_id)
|
||
continue;
|
||
|
||
e = strstrafter(line, " - ");
|
||
if (!e)
|
||
continue;
|
||
|
||
/* accept any name that starts with the currently expected type */
|
||
if (startswith(e, "devtmpfs"))
|
||
return true;
|
||
}
|
||
|
||
return false;
|
||
}
|
||
|
||
static int mount_fd(
|
||
const char *source,
|
||
int target_fd,
|
||
const char *filesystemtype,
|
||
unsigned long mountflags,
|
||
const void *data) {
|
||
|
||
assert(target_fd >= 0);
|
||
|
||
if (mount(source, FORMAT_PROC_FD_PATH(target_fd), filesystemtype, mountflags, data) < 0) {
|
||
if (errno != ENOENT)
|
||
return -errno;
|
||
|
||
/* ENOENT can mean two things: either that the source is missing, or that /proc/ isn't
|
||
* mounted. Check for the latter to generate better error messages. */
|
||
if (proc_mounted() == 0)
|
||
return -ENOSYS;
|
||
|
||
return -ENOENT;
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
int mount_nofollow(
|
||
const char *source,
|
||
const char *target,
|
||
const char *filesystemtype,
|
||
unsigned long mountflags,
|
||
const void *data) {
|
||
|
||
_cleanup_close_ int fd = -EBADF;
|
||
|
||
assert(target);
|
||
|
||
/* In almost all cases we want to manipulate the mount table without following symlinks, hence
|
||
* mount_nofollow() is usually the way to go. The only exceptions are environments where /proc/ is
|
||
* not available yet, since we need /proc/self/fd/ for this logic to work. i.e. during the early
|
||
* initialization of namespacing/container stuff where /proc is not yet mounted (and maybe even the
|
||
* fs to mount) we can only use traditional mount() directly.
|
||
*
|
||
* Note that this disables following only for the final component of the target, i.e symlinks within
|
||
* the path of the target are honoured, as are symlinks in the source path everywhere. */
|
||
|
||
fd = open(target, O_PATH|O_CLOEXEC|O_NOFOLLOW);
|
||
if (fd < 0)
|
||
return -errno;
|
||
|
||
return mount_fd(source, fd, filesystemtype, mountflags, data);
|
||
}
|
||
|
||
const char* mount_propagation_flag_to_string(unsigned long flags) {
|
||
|
||
switch (flags & (MS_SHARED|MS_SLAVE|MS_PRIVATE)) {
|
||
case 0:
|
||
return "";
|
||
case MS_SHARED:
|
||
return "shared";
|
||
case MS_SLAVE:
|
||
return "slave";
|
||
case MS_PRIVATE:
|
||
return "private";
|
||
}
|
||
|
||
return NULL;
|
||
}
|
||
|
||
int mount_propagation_flag_from_string(const char *name, unsigned long *ret) {
|
||
|
||
if (isempty(name))
|
||
*ret = 0;
|
||
else if (streq(name, "shared"))
|
||
*ret = MS_SHARED;
|
||
else if (streq(name, "slave"))
|
||
*ret = MS_SLAVE;
|
||
else if (streq(name, "private"))
|
||
*ret = MS_PRIVATE;
|
||
else
|
||
return -EINVAL;
|
||
return 0;
|
||
}
|
||
|
||
bool mount_propagation_flag_is_valid(unsigned long flag) {
|
||
return IN_SET(flag, 0, MS_SHARED, MS_PRIVATE, MS_SLAVE);
|
||
}
|
||
|
||
bool mount_new_api_supported(void) {
|
||
static int cache = -1;
|
||
int r;
|
||
|
||
if (cache >= 0)
|
||
return cache;
|
||
|
||
/* This is the newer API among the ones we use, so use it as boundary */
|
||
r = RET_NERRNO(mount_setattr(-EBADF, NULL, 0, NULL, 0));
|
||
if (r == 0 || ERRNO_IS_NOT_SUPPORTED(r)) /* This should return an error if it is working properly */
|
||
return (cache = false);
|
||
|
||
return (cache = true);
|
||
}
|
||
|
||
unsigned long ms_nosymfollow_supported(void) {
|
||
_cleanup_close_ int fsfd = -EBADF, mntfd = -EBADF;
|
||
static int cache = -1;
|
||
|
||
/* Returns MS_NOSYMFOLLOW if it is supported, zero otherwise. */
|
||
|
||
if (cache >= 0)
|
||
return cache ? MS_NOSYMFOLLOW : 0;
|
||
|
||
if (!mount_new_api_supported())
|
||
goto not_supported;
|
||
|
||
/* Checks if MS_NOSYMFOLLOW is supported (which was added in 5.10). We use the new mount API's
|
||
* mount_setattr() call for that, which was added in 5.12, which is close enough. */
|
||
|
||
fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC);
|
||
if (fsfd < 0) {
|
||
if (ERRNO_IS_NOT_SUPPORTED(errno))
|
||
goto not_supported;
|
||
|
||
log_debug_errno(errno, "Failed to open superblock context for tmpfs: %m");
|
||
return 0;
|
||
}
|
||
|
||
if (fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) < 0) {
|
||
if (ERRNO_IS_NOT_SUPPORTED(errno))
|
||
goto not_supported;
|
||
|
||
log_debug_errno(errno, "Failed to create tmpfs superblock: %m");
|
||
return 0;
|
||
}
|
||
|
||
mntfd = fsmount(fsfd, FSMOUNT_CLOEXEC, 0);
|
||
if (mntfd < 0) {
|
||
if (ERRNO_IS_NOT_SUPPORTED(errno))
|
||
goto not_supported;
|
||
|
||
log_debug_errno(errno, "Failed to turn superblock fd into mount fd: %m");
|
||
return 0;
|
||
}
|
||
|
||
if (mount_setattr(mntfd, "", AT_EMPTY_PATH|AT_RECURSIVE,
|
||
&(struct mount_attr) {
|
||
.attr_set = MOUNT_ATTR_NOSYMFOLLOW,
|
||
}, sizeof(struct mount_attr)) < 0) {
|
||
if (ERRNO_IS_NOT_SUPPORTED(errno))
|
||
goto not_supported;
|
||
|
||
log_debug_errno(errno, "Failed to set MOUNT_ATTR_NOSYMFOLLOW mount attribute: %m");
|
||
return 0;
|
||
}
|
||
|
||
cache = true;
|
||
return MS_NOSYMFOLLOW;
|
||
|
||
not_supported:
|
||
cache = false;
|
||
return 0;
|
||
}
|
||
|
||
int mount_option_supported(const char *fstype, const char *key, const char *value) {
|
||
_cleanup_close_ int fd = -EBADF;
|
||
int r;
|
||
|
||
/* Checks if the specified file system supports a mount option. Returns > 0 if it supports it, == 0 if
|
||
* it does not. Return -EAGAIN if we can't determine it. And any other error otherwise. */
|
||
|
||
assert(fstype);
|
||
assert(key);
|
||
|
||
fd = fsopen(fstype, FSOPEN_CLOEXEC);
|
||
if (fd < 0)
|
||
return log_debug_errno(errno, "Failed to open superblock context for '%s': %m", fstype);
|
||
|
||
/* Various file systems support fs context only in recent kernels (e.g. btrfs). For older kernels
|
||
* fsconfig() with FSCONFIG_SET_STRING/FSCONFIG_SET_FLAG never fail. Which sucks, because we want to
|
||
* use it for testing support, after all. Let's hence do a check if the file system got converted yet
|
||
* first. */
|
||
if (fsconfig(fd, FSCONFIG_SET_FD, "adefinitelynotexistingmountoption", NULL, fd) < 0) {
|
||
/* If FSCONFIG_SET_FD is not supported for the fs, then the file system was not converted to
|
||
* the new mount API yet. If it returns EINVAL the mount option doesn't exist, but the fstype
|
||
* is converted. */
|
||
if (errno == EOPNOTSUPP)
|
||
return -EAGAIN; /* fs not converted to new mount API → don't know */
|
||
if (errno != EINVAL)
|
||
return log_debug_errno(errno, "Failed to check if file system '%s' has been converted to new mount API: %m", fstype);
|
||
|
||
/* So FSCONFIG_SET_FD worked, but the option didn't exist (we got EINVAL), this means the fs
|
||
* is converted. Let's now ask the actual question we wonder about. */
|
||
} else
|
||
return log_debug_errno(SYNTHETIC_ERRNO(EAGAIN), "FSCONFIG_SET_FD worked unexpectedly for '%s', whoa!", fstype);
|
||
|
||
if (value)
|
||
r = fsconfig(fd, FSCONFIG_SET_STRING, key, value, 0);
|
||
else
|
||
r = fsconfig(fd, FSCONFIG_SET_FLAG, key, NULL, 0);
|
||
if (r < 0) {
|
||
if (errno == EINVAL)
|
||
return false; /* EINVAL means option not supported. */
|
||
|
||
return log_debug_errno(errno, "Failed to set '%s%s%s' on '%s' superblock context: %m",
|
||
key, value ? "=" : "", strempty(value), fstype);
|
||
}
|
||
|
||
return true; /* works! */
|
||
}
|
||
|
||
bool path_below_api_vfs(const char *p) {
|
||
assert(p);
|
||
|
||
/* API VFS are either directly mounted on any of these three paths, or below it. */
|
||
return PATH_STARTSWITH_SET(p, "/dev", "/sys", "/proc");
|
||
}
|