src/shared/mount-util.h

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2 #pragma once
   3
   4 #include <mntent.h>
   5 #include <stdio.h>
   6 #include <sys/stat.h>
   7 #include <unistd.h>
   8
   9 #include "alloc-util.h"
  10 #include "dissect-image.h"
  11 #include "errno-util.h"
  12 #include "macro.h"
  13
  14 /* The limit used for /dev itself. 4MB should be enough since device nodes and symlinks don't
  15  * consume any space and udev isn't supposed to create regular file either. There's no limit on the
  16  * max number of inodes since such limit is hard to guess especially on large storage array
  17  * systems. */
  18 #define TMPFS_LIMITS_DEV             ",size=4m"
  19
  20 /* The limit used for /dev in private namespaces. 4MB for contents of regular files. The number of
  21  * inodes should be relatively low in private namespaces but for now use a 64k limit. */
  22 #define TMPFS_LIMITS_PRIVATE_DEV     ",size=4m,nr_inodes=64k"
  23
  24 /* Very little, if any use expected */
  25 #define TMPFS_LIMITS_EMPTY_OR_ALMOST ",size=4m,nr_inodes=1k"
  26 #define TMPFS_LIMITS_SYS             TMPFS_LIMITS_EMPTY_OR_ALMOST
  27 #define TMPFS_LIMITS_SYS_FS_CGROUP   TMPFS_LIMITS_EMPTY_OR_ALMOST
  28
  29 /* On an extremely small device with only 256MB of RAM, 20% of RAM should be enough for the re-execution of
  30  * PID1 because 16MB of free space is required. */
  31 #define TMPFS_LIMITS_RUN             ",size=20%,nr_inodes=800k"
  32
  33 /* The limit used for various nested tmpfs mounts, in particular for guests started by systemd-nspawn.
  34  * 10% of RAM (using 16GB of RAM as a baseline) translates to 400k inodes (assuming 4k each) and 25%
  35  * translates to 1M inodes.
  36  * (On the host, /tmp is configured through a .mount unit file.) */
  37 #define NESTED_TMPFS_LIMITS          ",size=10%,nr_inodes=400k"
  38
  39 /* More space for volatile root and /var */
  40 #define TMPFS_LIMITS_VAR             ",size=25%,nr_inodes=1m"
  41 #define TMPFS_LIMITS_ROOTFS          TMPFS_LIMITS_VAR
  42 #define TMPFS_LIMITS_VOLATILE_STATE  TMPFS_LIMITS_VAR
  43
  44 int mount_fd(const char *source, int target_fd, const char *filesystemtype, unsigned long mountflags, const void *data);
  45 int mount_nofollow(const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data);
  46
  47 int repeat_unmount(const char *path, int flags);
  48 int umount_recursive(const char *target, int flags);
  49
  50 int bind_remount_recursive_with_mountinfo(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list, FILE *proc_self_mountinfo);
  51 static inline int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list) {
  52         return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, deny_list, NULL);
  53 }
  54
  55 int bind_remount_one_with_mountinfo(const char *path, unsigned long new_flags, unsigned long flags_mask, FILE *proc_self_mountinfo);
  56
  57 int mount_move_root(const char *path);
  58 int mount_pivot_root(const char *path);
  59
  60 DEFINE_TRIVIAL_CLEANUP_FUNC_FULL(FILE*, endmntent, NULL);
  61 #define _cleanup_endmntent_ _cleanup_(endmntentp)
  62
  63 int mount_verbose_full(
  64                 int error_log_level,
  65                 const char *what,
  66                 const char *where,
  67                 const char *type,
  68                 unsigned long flags,
  69                 const char *options,
  70                 bool follow_symlink);
  71
  72 static inline int mount_follow_verbose(
  73                 int error_log_level,
  74                 const char *what,
  75                 const char *where,
  76                 const char *type,
  77                 unsigned long flags,
  78                 const char *options) {
  79         return mount_verbose_full(error_log_level, what, where, type, flags, options, true);
  80 }
  81
  82 static inline int mount_nofollow_verbose(
  83                 int error_log_level,
  84                 const char *what,
  85                 const char *where,
  86                 const char *type,
  87                 unsigned long flags,
  88                 const char *options) {
  89         return mount_verbose_full(error_log_level, what, where, type, flags, options, false);
  90 }
  91
  92 int umount_verbose(
  93                 int error_log_level,
  94                 const char *where,
  95                 int flags);
  96
  97 int mount_option_mangle(
  98                 const char *options,
  99                 unsigned long mount_flags,
 100                 unsigned long *ret_mount_flags,
 101                 char **ret_remaining_options);
 102
 103 int mode_to_inaccessible_node(const char *runtime_dir, mode_t mode, char **dest);
 104 int mount_flags_to_string(unsigned long flags, char **ret);
 105
 106 /* Useful for usage with _cleanup_(), unmounts, removes a directory and frees the pointer */
 107 static inline char* umount_and_rmdir_and_free(char *p) {
 108         PROTECT_ERRNO;
 109         if (p) {
 110                 (void) umount_recursive(p, 0);
 111                 (void) rmdir(p);
 112         }
 113         return mfree(p);
 114 }
 115 DEFINE_TRIVIAL_CLEANUP_FUNC(char*, umount_and_rmdir_and_free);
 116
 117 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);
 118 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);
 119
 120 int make_mount_point(const char *path);
 121
 122 typedef enum RemountIdmapping {
 123         REMOUNT_IDMAPPING_NONE,
 124         /* Include a mapping from UID_MAPPED_ROOT (i.e. UID 2^31-2) on the backing fs to UID 0 on the
 125          * uidmapped fs. This is useful to ensure that the host root user can safely add inodes to the
 126          * uidmapped fs (which otherwise wouldn't work as the host root user is not defined on the uidmapped
 127          * mount and any attempts to create inodes will then be refused with EOVERFLOW). The idea is that
 128          * these inodes are quickly re-chown()ed to more suitable UIDs/GIDs. Any code that intends to be able
 129          * to add inodes to file systems mapped this way should set this flag, but given it comes with
 130          * certain security implications defaults to off, and requires explicit opt-in. */
 131         REMOUNT_IDMAPPING_HOST_ROOT,
 132         /* Define a mapping from root user within the container to the owner of the bind mounted directory.
 133          * This ensure no root-owned files will be written in a bind-mounted directory owned by a different
 134          * user. No other users are mapped. */
 135         REMOUNT_IDMAPPING_HOST_OWNER,
 136         _REMOUNT_IDMAPPING_MAX,
 137         _REMOUNT_IDMAPPING_INVALID = -EINVAL,
 138 } RemountIdmapping;
 139
 140 int remount_idmap(const char *p, uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping);
 141
 142 /* Creates a mount point (not parents) based on the source path or stat - ie, a file or a directory */
 143 int make_mount_point_inode_from_stat(const struct stat *st, const char *dest, mode_t mode);
 144 int make_mount_point_inode_from_path(const char *source, const char *dest, mode_t mode);