95231c7215
So the currentl and only fd_is_mount_point() check is actually entirely bogus: it passes "/" as filename argument, but that's not actually a a valid filename, but an absolute path. fd_is_mount_point() is written in a way tha the fd refers to a directory and the specified path is a file directly below it that shall be checked. The test call actually violated that rule, but still expected success. Let's fix this, and check for this explicitly, and refuse it. Let's extend the test and move it to test-mountpoint-util.c where the rest of the tests for related calls are placed. Replaces: #18004 Fixes: #17950
512 lines
19 KiB
C
512 lines
19 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
|
|
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <sys/mount.h>
|
|
|
|
#include "alloc-util.h"
|
|
#include "fd-util.h"
|
|
#include "fileio.h"
|
|
#include "fs-util.h"
|
|
#include "missing_stat.h"
|
|
#include "missing_syscall.h"
|
|
#include "mountpoint-util.h"
|
|
#include "parse-util.h"
|
|
#include "path-util.h"
|
|
#include "stat-util.h"
|
|
#include "stdio-util.h"
|
|
#include "strv.h"
|
|
|
|
/* This is the original MAX_HANDLE_SZ definition from the kernel, when the API was introduced. We use that in place of
|
|
* any more currently defined value to future-proof things: if the size is increased in the API headers, and our code
|
|
* is recompiled then it would cease working on old kernels, as those refuse any sizes larger than this value with
|
|
* EINVAL right-away. Hence, let's disconnect ourselves from any such API changes, and stick to the original definition
|
|
* from when it was introduced. We use it as a start value only anyway (see below), and hence should be able to deal
|
|
* with large file handles anyway. */
|
|
#define ORIGINAL_MAX_HANDLE_SZ 128
|
|
|
|
int name_to_handle_at_loop(
|
|
int fd,
|
|
const char *path,
|
|
struct file_handle **ret_handle,
|
|
int *ret_mnt_id,
|
|
int flags) {
|
|
|
|
_cleanup_free_ struct file_handle *h = NULL;
|
|
size_t n = ORIGINAL_MAX_HANDLE_SZ;
|
|
|
|
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
|
|
|
|
/* We need to invoke name_to_handle_at() in a loop, given that it might return EOVERFLOW when the specified
|
|
* buffer is too small. Note that in contrast to what the docs might suggest, MAX_HANDLE_SZ is only good as a
|
|
* start value, it is not an upper bound on the buffer size required.
|
|
*
|
|
* This improves on raw name_to_handle_at() also in one other regard: ret_handle and ret_mnt_id can be passed
|
|
* as NULL if there's no interest in either. */
|
|
|
|
for (;;) {
|
|
int mnt_id = -1;
|
|
|
|
h = malloc0(offsetof(struct file_handle, f_handle) + n);
|
|
if (!h)
|
|
return -ENOMEM;
|
|
|
|
h->handle_bytes = n;
|
|
|
|
if (name_to_handle_at(fd, path, h, &mnt_id, flags) >= 0) {
|
|
|
|
if (ret_handle)
|
|
*ret_handle = TAKE_PTR(h);
|
|
|
|
if (ret_mnt_id)
|
|
*ret_mnt_id = mnt_id;
|
|
|
|
return 0;
|
|
}
|
|
if (errno != EOVERFLOW)
|
|
return -errno;
|
|
|
|
if (!ret_handle && ret_mnt_id && mnt_id >= 0) {
|
|
|
|
/* As it appears, name_to_handle_at() fills in mnt_id even when it returns EOVERFLOW when the
|
|
* buffer is too small, but that's undocumented. Hence, let's make use of this if it appears to
|
|
* be filled in, and the caller was interested in only the mount ID an nothing else. */
|
|
|
|
*ret_mnt_id = mnt_id;
|
|
return 0;
|
|
}
|
|
|
|
/* If name_to_handle_at() didn't increase the byte size, then this EOVERFLOW is caused by something
|
|
* else (apparently EOVERFLOW is returned for untriggered nfs4 mounts sometimes), not by the too small
|
|
* buffer. In that case propagate EOVERFLOW */
|
|
if (h->handle_bytes <= n)
|
|
return -EOVERFLOW;
|
|
|
|
/* The buffer was too small. Size the new buffer by what name_to_handle_at() returned. */
|
|
n = h->handle_bytes;
|
|
if (offsetof(struct file_handle, f_handle) + n < n) /* check for addition overflow */
|
|
return -EOVERFLOW;
|
|
|
|
h = mfree(h);
|
|
}
|
|
}
|
|
|
|
static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *ret_mnt_id) {
|
|
char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
|
|
_cleanup_free_ char *fdinfo = NULL;
|
|
_cleanup_close_ int subfd = -1;
|
|
char *p;
|
|
int r;
|
|
|
|
assert(ret_mnt_id);
|
|
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
|
|
|
|
if ((flags & AT_EMPTY_PATH) && isempty(filename))
|
|
xsprintf(path, "/proc/self/fdinfo/%i", fd);
|
|
else {
|
|
subfd = openat(fd, filename, O_CLOEXEC|O_PATH|(flags & AT_SYMLINK_FOLLOW ? 0 : O_NOFOLLOW));
|
|
if (subfd < 0)
|
|
return -errno;
|
|
|
|
xsprintf(path, "/proc/self/fdinfo/%i", subfd);
|
|
}
|
|
|
|
r = read_full_file(path, &fdinfo, NULL);
|
|
if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
|
|
return -EOPNOTSUPP;
|
|
if (r < 0)
|
|
return r;
|
|
|
|
p = startswith(fdinfo, "mnt_id:");
|
|
if (!p) {
|
|
p = strstr(fdinfo, "\nmnt_id:");
|
|
if (!p) /* The mnt_id field is a relatively new addition */
|
|
return -EOPNOTSUPP;
|
|
|
|
p += 8;
|
|
}
|
|
|
|
p += strspn(p, WHITESPACE);
|
|
p[strcspn(p, WHITESPACE)] = 0;
|
|
|
|
return safe_atoi(p, ret_mnt_id);
|
|
}
|
|
|
|
static bool filename_possibly_with_slash_suffix(const char *s) {
|
|
const char *slash, *copied;
|
|
|
|
/* Checks whether the specified string is either file name, or a filename with a suffix of
|
|
* slashes. But nothing else.
|
|
*
|
|
* this is OK: foo, bar, foo/, bar/, foo//, bar///
|
|
* this is not OK: "", "/", "/foo", "foo/bar", ".", ".." … */
|
|
|
|
slash = strchr(s, '/');
|
|
if (!slash)
|
|
return filename_is_valid(s);
|
|
|
|
if (slash - s > FILENAME_MAX) /* We want to allocate on the stack below, hence do a size check first */
|
|
return false;
|
|
|
|
if (slash[strspn(slash, "/")] != 0) /* Check that the suffix consist only of one or more slashes */
|
|
return false;
|
|
|
|
copied = strndupa(s, slash - s);
|
|
return filename_is_valid(copied);
|
|
}
|
|
|
|
int fd_is_mount_point(int fd, const char *filename, int flags) {
|
|
_cleanup_free_ struct file_handle *h = NULL, *h_parent = NULL;
|
|
int mount_id = -1, mount_id_parent = -1;
|
|
bool nosupp = false, check_st_dev = true;
|
|
STRUCT_STATX_DEFINE(sx);
|
|
struct stat a, b;
|
|
int r;
|
|
|
|
assert(fd >= 0);
|
|
assert(filename);
|
|
assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
|
|
|
|
/* Insist that the specified filename is actually a filename, and not a path, i.e. some inode further
|
|
* up or down the tree then immediately below the specified directory fd. */
|
|
if (!filename_possibly_with_slash_suffix(filename))
|
|
return -EINVAL;
|
|
|
|
/* First we will try statx()' STATX_ATTR_MOUNT_ROOT attribute, which is our ideal API, available
|
|
* since kernel 5.8.
|
|
*
|
|
* If that fails, our second try is the name_to_handle_at() syscall, which tells us the mount id and
|
|
* an opaque file "handle". It is not supported everywhere though (kernel compile-time option, not
|
|
* all file systems are hooked up). If it works the mount id is usually good enough to tell us
|
|
* whether something is a mount point.
|
|
*
|
|
* If that didn't work we will try to read the mount id from /proc/self/fdinfo/<fd>. This is almost
|
|
* as good as name_to_handle_at(), however, does not return the opaque file handle. The opaque file
|
|
* handle is pretty useful to detect the root directory, which we should always consider a mount
|
|
* point. Hence we use this only as fallback. Exporting the mnt_id in fdinfo is a pretty recent
|
|
* kernel addition.
|
|
*
|
|
* As last fallback we do traditional fstat() based st_dev comparisons. This is how things were
|
|
* traditionally done, but unionfs breaks this since it exposes file systems with a variety of st_dev
|
|
* reported. Also, btrfs subvolumes have different st_dev, even though they aren't real mounts of
|
|
* their own. */
|
|
|
|
if (statx(fd, filename, (FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW) |
|
|
(flags & AT_EMPTY_PATH) |
|
|
AT_NO_AUTOMOUNT, 0, &sx) < 0) {
|
|
if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno))
|
|
return -errno;
|
|
|
|
/* If statx() is not available or forbidden, fall back to name_to_handle_at() below */
|
|
} else if (FLAGS_SET(sx.stx_attributes_mask, STATX_ATTR_MOUNT_ROOT)) /* yay! */
|
|
return FLAGS_SET(sx.stx_attributes, STATX_ATTR_MOUNT_ROOT);
|
|
|
|
r = name_to_handle_at_loop(fd, filename, &h, &mount_id, flags);
|
|
if (IN_SET(r, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL))
|
|
/* This kernel does not support name_to_handle_at() at all (ENOSYS), or the syscall was blocked
|
|
* (EACCES/EPERM; maybe through seccomp, because we are running inside of a container?), or the mount
|
|
* point is not triggered yet (EOVERFLOW, think nfs4), or some general name_to_handle_at() flakiness
|
|
* (EINVAL): fall back to simpler logic. */
|
|
goto fallback_fdinfo;
|
|
else if (r == -EOPNOTSUPP)
|
|
/* This kernel or file system does not support name_to_handle_at(), hence let's see if the upper fs
|
|
* supports it (in which case it is a mount point), otherwise fall back to the traditional stat()
|
|
* logic */
|
|
nosupp = true;
|
|
else if (r < 0)
|
|
return r;
|
|
|
|
r = name_to_handle_at_loop(fd, "", &h_parent, &mount_id_parent, AT_EMPTY_PATH);
|
|
if (r == -EOPNOTSUPP) {
|
|
if (nosupp)
|
|
/* Neither parent nor child do name_to_handle_at()? We have no choice but to fall back. */
|
|
goto fallback_fdinfo;
|
|
else
|
|
/* The parent can't do name_to_handle_at() but the directory we are interested in can? If so,
|
|
* it must be a mount point. */
|
|
return 1;
|
|
} else if (r < 0)
|
|
return r;
|
|
|
|
/* The parent can do name_to_handle_at() but the
|
|
* directory we are interested in can't? If so, it
|
|
* must be a mount point. */
|
|
if (nosupp)
|
|
return 1;
|
|
|
|
/* If the file handle for the directory we are
|
|
* interested in and its parent are identical, we
|
|
* assume this is the root directory, which is a mount
|
|
* point. */
|
|
|
|
if (h->handle_bytes == h_parent->handle_bytes &&
|
|
h->handle_type == h_parent->handle_type &&
|
|
memcmp(h->f_handle, h_parent->f_handle, h->handle_bytes) == 0)
|
|
return 1;
|
|
|
|
return mount_id != mount_id_parent;
|
|
|
|
fallback_fdinfo:
|
|
r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
|
|
if (IN_SET(r, -EOPNOTSUPP, -EACCES, -EPERM))
|
|
goto fallback_fstat;
|
|
if (r < 0)
|
|
return r;
|
|
|
|
r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
if (mount_id != mount_id_parent)
|
|
return 1;
|
|
|
|
/* Hmm, so, the mount ids are the same. This leaves one
|
|
* special case though for the root file system. For that,
|
|
* let's see if the parent directory has the same inode as we
|
|
* are interested in. Hence, let's also do fstat() checks now,
|
|
* too, but avoid the st_dev comparisons, since they aren't
|
|
* that useful on unionfs mounts. */
|
|
check_st_dev = false;
|
|
|
|
fallback_fstat:
|
|
/* yay for fstatat() taking a different set of flags than the other
|
|
* _at() above */
|
|
if (flags & AT_SYMLINK_FOLLOW)
|
|
flags &= ~AT_SYMLINK_FOLLOW;
|
|
else
|
|
flags |= AT_SYMLINK_NOFOLLOW;
|
|
if (fstatat(fd, filename, &a, flags) < 0)
|
|
return -errno;
|
|
|
|
if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0)
|
|
return -errno;
|
|
|
|
/* A directory with same device and inode as its parent? Must
|
|
* be the root directory */
|
|
if (a.st_dev == b.st_dev &&
|
|
a.st_ino == b.st_ino)
|
|
return 1;
|
|
|
|
return check_st_dev && (a.st_dev != b.st_dev);
|
|
}
|
|
|
|
/* flags can be AT_SYMLINK_FOLLOW or 0 */
|
|
int path_is_mount_point(const char *t, const char *root, int flags) {
|
|
_cleanup_free_ char *canonical = NULL;
|
|
_cleanup_close_ int fd = -1;
|
|
int r;
|
|
|
|
assert(t);
|
|
assert((flags & ~AT_SYMLINK_FOLLOW) == 0);
|
|
|
|
if (path_equal(t, "/"))
|
|
return 1;
|
|
|
|
/* we need to resolve symlinks manually, we can't just rely on
|
|
* fd_is_mount_point() to do that for us; if we have a structure like
|
|
* /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
|
|
* look at needs to be /usr, not /. */
|
|
if (flags & AT_SYMLINK_FOLLOW) {
|
|
r = chase_symlinks(t, root, CHASE_TRAIL_SLASH, &canonical, NULL);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
t = canonical;
|
|
}
|
|
|
|
fd = open_parent(t, O_PATH|O_CLOEXEC, 0);
|
|
if (fd < 0)
|
|
return fd;
|
|
|
|
return fd_is_mount_point(fd, last_path_component(t), flags);
|
|
}
|
|
|
|
int path_get_mnt_id(const char *path, int *ret) {
|
|
STRUCT_NEW_STATX_DEFINE(buf);
|
|
int r;
|
|
|
|
if (statx(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW|AT_NO_AUTOMOUNT, STATX_MNT_ID, &buf.sx) < 0) {
|
|
if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno))
|
|
return -errno;
|
|
|
|
/* Fall back to name_to_handle_at() and then fdinfo if statx is not supported or we lack
|
|
* privileges */
|
|
|
|
} else if (FLAGS_SET(buf.nsx.stx_mask, STATX_MNT_ID)) {
|
|
*ret = buf.nsx.stx_mnt_id;
|
|
return 0;
|
|
}
|
|
|
|
r = name_to_handle_at_loop(AT_FDCWD, path, NULL, ret, 0);
|
|
if (IN_SET(r, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL)) /* kernel/fs don't support this, or seccomp blocks access, or untriggered mount, or name_to_handle_at() is flaky */
|
|
return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret);
|
|
|
|
return r;
|
|
}
|
|
|
|
bool fstype_is_network(const char *fstype) {
|
|
const char *x;
|
|
|
|
x = startswith(fstype, "fuse.");
|
|
if (x)
|
|
fstype = x;
|
|
|
|
return STR_IN_SET(fstype,
|
|
"afs",
|
|
"ceph",
|
|
"cifs",
|
|
"smb3",
|
|
"smbfs",
|
|
"sshfs",
|
|
"ncpfs",
|
|
"ncp",
|
|
"nfs",
|
|
"nfs4",
|
|
"gfs",
|
|
"gfs2",
|
|
"glusterfs",
|
|
"pvfs2", /* OrangeFS */
|
|
"ocfs2",
|
|
"lustre",
|
|
"davfs");
|
|
}
|
|
|
|
bool fstype_is_api_vfs(const char *fstype) {
|
|
return STR_IN_SET(fstype,
|
|
"autofs",
|
|
"bpf",
|
|
"cgroup",
|
|
"cgroup2",
|
|
"configfs",
|
|
"cpuset",
|
|
"debugfs",
|
|
"devpts",
|
|
"devtmpfs",
|
|
"efivarfs",
|
|
"fusectl",
|
|
"hugetlbfs",
|
|
"mqueue",
|
|
"proc",
|
|
"pstore",
|
|
"ramfs",
|
|
"securityfs",
|
|
"sysfs",
|
|
"tmpfs",
|
|
"tracefs");
|
|
}
|
|
|
|
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",
|
|
"iso9660",
|
|
"squashfs");
|
|
}
|
|
|
|
bool fstype_can_discard(const char *fstype) {
|
|
return STR_IN_SET(fstype,
|
|
"btrfs",
|
|
"ext4",
|
|
"vfat",
|
|
"xfs");
|
|
}
|
|
|
|
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. */
|
|
|
|
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 < 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 = strstr(line, " - ");
|
|
if (!e)
|
|
continue;
|
|
|
|
/* accept any name that starts with the currently expected type */
|
|
if (startswith(e + 3, "devtmpfs"))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
const char *mount_propagation_flags_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_flags_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;
|
|
}
|