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   mount_setattr    ( 2 )

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Примеры (Examples)

/*
        * This program allows the caller to create a new detached mount
        * and set various properties on it.
        */
       #define _GNU_SOURCE
       #include <errno.h>
       #include <fcntl.h>
       #include <getopt.h>
       #include <linux/mount.h>
       #include <linux/types.h>
       #include <stdbool.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <sys/syscall.h>
       #include <unistd.h>

       static inline int
       mount_setattr(int dirfd, const char *pathname, unsigned int flags,
                     struct mount_attr *attr, size_t size)
       {
           return syscall(SYS_mount_setattr, dirfd, pathname, flags,
                          attr, size);
       }

       static inline int
       open_tree(int dirfd, const char *filename, unsigned int flags)
       {
           return syscall(SYS_open_tree, dirfd, filename, flags);
       }

       static inline int
       move_mount(int from_dirfd, const char *from_pathname,
                  int to_dirfd, const char *to_pathname, unsigned int flags)
       {
           return syscall(SYS_move_mount, from_dirfd, from_pathname,
                          to_dirfd, to_pathname, flags);
       }

       static const struct option longopts[] = {
           {"map-mount",       required_argument,  NULL,  'a'},
           {"recursive",       no_argument,        NULL,  'b'},
           {"read-only",       no_argument,        NULL,  'c'},
           {"block-setid",     no_argument,        NULL,  'd'},
           {"block-devices",   no_argument,        NULL,  'e'},
           {"block-exec",      no_argument,        NULL,  'f'},
           {"no-access-time",  no_argument,        NULL,  'g'},
           { NULL,             0,                  NULL,   0 },
       };

       #define exit_log(format, ...)  do           \
       {                                           \
           fprintf(stderr, format, ##__VA_ARGS__); \
           exit(EXIT_FAILURE);                     \
       } while (0)

       int
       main(int argc, char *argv[])
       {
           struct mount_attr *attr = &(struct mount_attr){};
           int fd_userns = -1;
           bool recursive = false;
           int index = 0;
           int ret;

           while ((ret = getopt_long_only(argc, argv, "",
                                          longopts, &index)) != -1) {
               switch (ret) {
               case 'a':
                   fd_userns = open(optarg, O_RDONLY | O_CLOEXEC);
                   if (fd_userns == -1)
                       exit_log("%m - Failed top open %s\n", optarg);
                   break;
               case 'b':
                   recursive = true;
                   break;
               case 'c':
                   attr->attr_set |= MOUNT_ATTR_RDONLY;
                   break;
               case 'd':
                   attr->attr_set |= MOUNT_ATTR_NOSUID;
                   break;
               case 'e':
                   attr->attr_set |= MOUNT_ATTR_NODEV;
                   break;
               case 'f':
                   attr->attr_set |= MOUNT_ATTR_NOEXEC;
                   break;
               case 'g':
                   attr->attr_set |= MOUNT_ATTR_NOATIME;
                   attr->attr_clr |= MOUNT_ATTR__ATIME;
                   break;
               default:
                   exit_log("Invalid argument specified");
               }
           }

           if ((argc - optind) < 2)
               exit_log("Missing source or target mount point\n");

           const char *source = argv[optind];
           const char *target = argv[optind + 1];

           /* In the following, -1 as the 'dirfd' argument ensures that
              open_tree() fails if 'source' is not an absolute pathname. */

           int fd_tree = open_tree(-1, source,
                              OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC |
                              AT_EMPTY_PATH | (recursive ? AT_RECURSIVE : 0));
           if (fd_tree == -1)
               exit_log("%m - Failed to open %s\n", source);

           if (fd_userns >= 0) {
               attr->attr_set  |= MOUNT_ATTR_IDMAP;
               attr->userns_fd = fd_userns;
           }

           ret = mount_setattr(fd_tree, "",
                               AT_EMPTY_PATH | (recursive ? AT_RECURSIVE : 0),
                               attr, sizeof(struct mount_attr));
           if (ret == -1)
               exit_log("%m - Failed to change mount attributes\n");

           close(fd_userns);

           /* In the following, -1 as the 'to_dirfd' argument ensures that
              open_tree() fails if 'target' is not an absolute pathname. */

           ret = move_mount(fd_tree, "", -1, target,
                            MOVE_MOUNT_F_EMPTY_PATH);
           if (ret == -1)
               exit_log("%m - Failed to attach mount to %s\n", target);

           close(fd_tree);

           exit(EXIT_SUCCESS);
       }