1 files changed, 143 insertions, 0 deletions
diff --git a/src/shared/mount-util.h b/src/shared/mount-util.h
new file mode 100644
index 0000000..8b07611
--- /dev/null
+++ b/src/shared/mount-util.h
@@ -0,0 +1,143 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <mntent.h>
+#include <stdio.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "dissect-image.h"
+#include "errno-util.h"
+#include "macro.h"
+
+/* The limit used for /dev itself. 4MB should be enough since device nodes and symlinks don't
+ * consume any space and udev isn't supposed to create regular file either. There's no limit on the
+ * max number of inodes since such limit is hard to guess especially on large storage array
+ * systems. */
+#define TMPFS_LIMITS_DEV             ",size=4m"
+
+/* The limit used for /dev in private namespaces. 4MB for contents of regular files. The number of
+ * inodes should be relatively low in private namespaces but for now use a 64k limit. */
+#define TMPFS_LIMITS_PRIVATE_DEV     ",size=4m,nr_inodes=64k"
+
+/* Very little, if any use expected */
+#define TMPFS_LIMITS_EMPTY_OR_ALMOST ",size=4m,nr_inodes=1k"
+#define TMPFS_LIMITS_SYS             TMPFS_LIMITS_EMPTY_OR_ALMOST
+#define TMPFS_LIMITS_SYS_FS_CGROUP   TMPFS_LIMITS_EMPTY_OR_ALMOST
+
+/* On an extremely small device with only 256MB of RAM, 20% of RAM should be enough for the re-execution of
+ * PID1 because 16MB of free space is required. */
+#define TMPFS_LIMITS_RUN             ",size=20%,nr_inodes=800k"
+
+/* The limit used for various nested tmpfs mounts, in particular for guests started by systemd-nspawn.
+ * 10% of RAM (using 16GB of RAM as a baseline) translates to 400k inodes (assuming 4k each) and 25%
+ * translates to 1M inodes.
+ * (On the host, /tmp is configured through a .mount unit file.) */
+#define NESTED_TMPFS_LIMITS          ",size=10%,nr_inodes=400k"
+
+/* More space for volatile root and /var */
+#define TMPFS_LIMITS_VAR             ",size=25%,nr_inodes=1m"
+#define TMPFS_LIMITS_ROOTFS          TMPFS_LIMITS_VAR
+#define TMPFS_LIMITS_VOLATILE_STATE  TMPFS_LIMITS_VAR
+
+int mount_fd(const char *source, int target_fd, const char *filesystemtype, unsigned long mountflags, const void *data);
+int mount_nofollow(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);
+
+int repeat_unmount(const char *path, int flags);
+int umount_recursive(const char *target, int flags);
+
+int bind_remount_recursive_with_mountinfo(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list, FILE *proc_self_mountinfo);
+static inline int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list) {
+        return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, deny_list, NULL);
+}
+
+int bind_remount_one_with_mountinfo(const char *path, unsigned long new_flags, unsigned long flags_mask, FILE *proc_self_mountinfo);
+
+int mount_move_root(const char *path);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(FILE*, endmntent, NULL);
+#define _cleanup_endmntent_ _cleanup_(endmntentp)
+
+int mount_verbose_full(
+                int error_log_level,
+                const char *what,
+                const char *where,
+                const char *type,
+                unsigned long flags,
+                const char *options,
+                bool follow_symlink);
+
+static inline int mount_follow_verbose(
+                int error_log_level,
+                const char *what,
+                const char *where,
+                const char *type,
+                unsigned long flags,
+                const char *options) {
+        return mount_verbose_full(error_log_level, what, where, type, flags, options, true);
+}
+
+static inline int mount_nofollow_verbose(
+                int error_log_level,
+                const char *what,
+                const char *where,
+                const char *type,
+                unsigned long flags,
+                const char *options) {
+        return mount_verbose_full(error_log_level, what, where, type, flags, options, false);
+}
+
+int umount_verbose(
+                int error_log_level,
+                const char *where,
+                int flags);
+
+int mount_option_mangle(
+                const char *options,
+                unsigned long mount_flags,
+                unsigned long *ret_mount_flags,
+                char **ret_remaining_options);
+
+int mode_to_inaccessible_node(const char *runtime_dir, mode_t mode, char **dest);
+int mount_flags_to_string(unsigned long flags, char **ret);
+
+/* Useful for usage with _cleanup_(), unmounts, removes a directory and frees the pointer */
+static inline char* umount_and_rmdir_and_free(char *p) {
+        PROTECT_ERRNO;
+        if (p) {
+                (void) umount_recursive(p, 0);
+                (void) rmdir(p);
+        }
+        return mfree(p);
+}
+DEFINE_TRIVIAL_CLEANUP_FUNC(char*, umount_and_rmdir_and_free);
+
+int bind_mount_in_namespace(pid_t target, const char *propagate_path, const char *incoming_path, const char *src, const char *dest, bool read_only, bool make_file_or_directory);
+int mount_image_in_namespace(pid_t target, const char *propagate_path, const char *incoming_path, const char *src, const char *dest, bool read_only, bool make_file_or_directory, const MountOptions *options);
+
+int make_mount_point(const char *path);
+
+typedef enum RemountIdmapping {
+        REMOUNT_IDMAPPING_NONE,
+        /* Include a mapping from UID_MAPPED_ROOT (i.e. UID 2^31-2) on the backing fs to UID 0 on the
+         * uidmapped fs. This is useful to ensure that the host root user can safely add inodes to the
+         * uidmapped fs (which otherwise wouldn't work as the host root user is not defined on the uidmapped
+         * mount and any attempts to create inodes will then be refused with EOVERFLOW). The idea is that
+         * these inodes are quickly re-chown()ed to more suitable UIDs/GIDs. Any code that intends to be able
+         * to add inodes to file systems mapped this way should set this flag, but given it comes with
+         * certain security implications defaults to off, and requires explicit opt-in. */
+        REMOUNT_IDMAPPING_HOST_ROOT,
+        /* Define a mapping from root user within the container to the owner of the bind mounted directory.
+         * This ensure no root-owned files will be written in a bind-mounted directory owned by a different
+         * user. No other users are mapped. */
+        REMOUNT_IDMAPPING_HOST_OWNER,
+        _REMOUNT_IDMAPPING_MAX,
+        _REMOUNT_IDMAPPING_INVALID = -EINVAL,
+} RemountIdmapping;
+
+int remount_idmap(const char *p, uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping);
+
+/* Creates a mount point (not parents) based on the source path or stat - ie, a file or a directory */
+int make_mount_point_inode_from_stat(const struct stat *st, const char *dest, mode_t mode);
+int make_mount_point_inode_from_path(const char *source, const char *dest, mode_t mode);