diff options
Diffstat (limited to 'src/shared/util.c')
| -rw-r--r-- | src/shared/util.c | 145 |
1 files changed, 144 insertions, 1 deletions
diff --git a/src/shared/util.c b/src/shared/util.c index 011fb36f4..7fa3742b4 100644 --- a/src/shared/util.c +++ b/src/shared/util.c @@ -6540,7 +6540,6 @@ int umount_recursive(const char *prefix, int flags) { "%*s" /* (11) mount options 2 */ "%*[^\n]", /* some rubbish at the end */ &path); - if (k != 1) { if (k == EOF) break; @@ -6570,3 +6569,147 @@ int umount_recursive(const char *prefix, int flags) { return r ? r : n; } + +int bind_remount_recursive(const char *prefix, bool ro) { + _cleanup_set_free_free_ Set *done = NULL; + _cleanup_free_ char *cleaned = NULL; + int r; + + /* Recursively remount a directory (and all its submounts) + * read-only or read-write. If the directory is already + * mounted, we reuse the mount and simply mark it + * MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write + * operation). If it isn't we first make it one. Afterwards we + * apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to all + * submounts we can access, too. When mounts are stacked on + * the same mount point we only care for each individual + * "top-level" mount on each point, as we cannot + * influence/access the underlying mounts anyway. We do not + * have any effect on future submounts that might get + * propagated, they migt be writable. This includes future + * submounts that have been triggered via autofs. */ + + cleaned = strdup(prefix); + if (!cleaned) + return -ENOMEM; + + path_kill_slashes(cleaned); + + done = set_new(string_hash_func, string_compare_func); + if (!done) + return -ENOMEM; + + for (;;) { + _cleanup_fclose_ FILE *proc_self_mountinfo = NULL; + _cleanup_set_free_free_ Set *todo = NULL; + bool top_autofs = false; + char *x; + + todo = set_new(string_hash_func, string_compare_func); + if (!todo) + return -ENOMEM; + + proc_self_mountinfo = fopen("/proc/self/mountinfo", "re"); + if (!proc_self_mountinfo) + return -errno; + + for (;;) { + _cleanup_free_ char *path = NULL, *p = NULL, *type = NULL; + int k; + + k = fscanf(proc_self_mountinfo, + "%*s " /* (1) mount id */ + "%*s " /* (2) parent id */ + "%*s " /* (3) major:minor */ + "%*s " /* (4) root */ + "%ms " /* (5) mount point */ + "%*s" /* (6) mount options (superblock) */ + "%*[^-]" /* (7) optional fields */ + "- " /* (8) separator */ + "%ms " /* (9) file system type */ + "%*s" /* (10) mount source */ + "%*s" /* (11) mount options (bind mount) */ + "%*[^\n]", /* some rubbish at the end */ + &path, + &type); + if (k != 2) { + if (k == EOF) + break; + + continue; + } + + p = cunescape(path); + if (!p) + return -ENOMEM; + + /* Let's ignore autofs mounts. If they aren't + * triggered yet, we want to avoid triggering + * them, as we don't make any guarantees for + * future submounts anyway. If they are + * already triggered, then we will find + * another entry for this. */ + if (streq(type, "autofs")) { + top_autofs = top_autofs || path_equal(cleaned, p); + continue; + } + + if (path_startswith(p, cleaned) && + !set_contains(done, p)) { + + r = set_consume(todo, p); + p = NULL; + + if (r == -EEXIST) + continue; + if (r < 0) + return r; + } + } + + /* If we have no submounts to process anymore and if + * the root is either already done, or an autofs, we + * are done */ + if (set_isempty(todo) && + (top_autofs || set_contains(done, cleaned))) + return 0; + + if (!set_contains(done, cleaned) && + !set_contains(todo, cleaned)) { + /* The prefix directory itself is not yet a + * mount, make it one. */ + if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0) + return -errno; + + if (mount(NULL, prefix, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) + return -errno; + + x = strdup(cleaned); + if (!x) + return -ENOMEM; + + r = set_consume(done, x); + if (r < 0) + return r; + } + + while ((x = set_steal_first(todo))) { + + r = set_consume(done, x); + if (r == -EEXIST) + continue; + if (r < 0) + return r; + + if (mount(NULL, x, NULL, MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) { + + /* Deal with mount points that are + * obstructed by a later mount */ + + if (errno != ENOENT) + return -errno; + } + + } + } +} |