Merge pull request #14532 from poettering/namespace-dynamic-user-fix
Make DynamicUser=1 work in a userns container
This commit is contained in:
commit
575a915a74
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@ -1063,14 +1063,6 @@ static int apply_mount(
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return 0;
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return 0;
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}
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}
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/* Change per-mount flags on an existing mount */
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static int bind_remount_one(const char *path, unsigned long orig_flags, unsigned long new_flags, unsigned long flags_mask) {
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if (mount(NULL, path, NULL, (orig_flags & ~flags_mask) | MS_REMOUNT | MS_BIND | new_flags, NULL) < 0)
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return -errno;
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return 0;
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}
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static int make_read_only(const MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) {
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static int make_read_only(const MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) {
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unsigned long new_flags = 0, flags_mask = 0;
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unsigned long new_flags = 0, flags_mask = 0;
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bool submounts = false;
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bool submounts = false;
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@ -1102,7 +1094,7 @@ static int make_read_only(const MountEntry *m, char **blacklist, FILE *proc_self
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if (submounts)
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if (submounts)
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r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, blacklist, proc_self_mountinfo);
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r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, blacklist, proc_self_mountinfo);
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else
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else
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r = bind_remount_one(mount_entry_path(m), m->flags, new_flags, flags_mask);
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r = bind_remount_one_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, proc_self_mountinfo);
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/* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked
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/* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked
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* read-only already stays this way. This improves compatibility with container managers, where we
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* read-only already stays this way. This improves compatibility with container managers, where we
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@ -76,35 +76,57 @@ int umount_recursive(const char *prefix, int flags) {
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return n;
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return n;
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}
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}
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/* Get the mount flags for the mountpoint at "path" from "table" */
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static int get_mount_flags(
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static int get_mount_flags(const char *path, unsigned long *flags, struct libmnt_table *table) {
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struct libmnt_table *table,
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struct statvfs buf = {};
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const char *path,
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struct libmnt_fs *fs = NULL;
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unsigned long *ret) {
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const char *opts = NULL;
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struct libmnt_fs *fs;
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struct statvfs buf;
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const char *opts;
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int r = 0;
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int r = 0;
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/* Get the mount flags for the mountpoint at "path" from "table". We have a fallback using statvfs()
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* in place (which provides us with mostly the same info), but it's just a fallback, since using it
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* means triggering autofs or NFS mounts, which we'd rather avoid needlessly. */
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fs = mnt_table_find_target(table, path, MNT_ITER_FORWARD);
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fs = mnt_table_find_target(table, path, MNT_ITER_FORWARD);
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if (!fs) {
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if (!fs) {
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log_warning("Could not find '%s' in mount table", path);
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log_debug("Could not find '%s' in mount table, ignoring.", path);
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goto fallback;
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goto fallback;
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}
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}
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opts = mnt_fs_get_vfs_options(fs);
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opts = mnt_fs_get_vfs_options(fs);
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r = mnt_optstr_get_flags(opts, flags, mnt_get_builtin_optmap(MNT_LINUX_MAP));
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if (!opts) {
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*ret = 0;
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return 0;
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}
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r = mnt_optstr_get_flags(opts, ret, mnt_get_builtin_optmap(MNT_LINUX_MAP));
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if (r != 0) {
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if (r != 0) {
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log_warning_errno(r, "Could not get flags for '%s': %m", path);
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log_debug_errno(r, "Could not get flags for '%s', ignoring: %m", path);
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goto fallback;
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goto fallback;
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}
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}
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/* relatime is default and trying to set it in an unprivileged container causes EPERM */
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/* MS_RELATIME is default and trying to set it in an unprivileged container causes EPERM */
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*flags &= ~MS_RELATIME;
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*ret &= ~MS_RELATIME;
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return 0;
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return 0;
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fallback:
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fallback:
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if (statvfs(path, &buf) < 0)
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if (statvfs(path, &buf) < 0)
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return -errno;
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return -errno;
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*flags = buf.f_flag;
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/* The statvfs() flags and the mount flags mostly have the same values, but for some cases do
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* not. Hence map the flags manually. (Strictly speaking, ST_RELATIME/MS_RELATIME is the most
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* prominent one that doesn't match, but that's the one we mask away anyway, see above.) */
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*ret =
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FLAGS_SET(buf.f_flag, ST_RDONLY) * MS_RDONLY |
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FLAGS_SET(buf.f_flag, ST_NODEV) * MS_NODEV |
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FLAGS_SET(buf.f_flag, ST_NOEXEC) * MS_NOEXEC |
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FLAGS_SET(buf.f_flag, ST_NOSUID) * MS_NOSUID |
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FLAGS_SET(buf.f_flag, ST_NOATIME) * MS_NOATIME |
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FLAGS_SET(buf.f_flag, ST_NODIRATIME) * MS_NODIRATIME;
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return 0;
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return 0;
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}
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}
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@ -118,9 +140,10 @@ int bind_remount_recursive_with_mountinfo(
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FILE *proc_self_mountinfo) {
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FILE *proc_self_mountinfo) {
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_cleanup_set_free_free_ Set *done = NULL;
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_cleanup_set_free_free_ Set *done = NULL;
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_cleanup_free_ char *cleaned = NULL;
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_cleanup_free_ char *simplified = NULL;
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int r;
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int r;
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assert(prefix);
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assert(proc_self_mountinfo);
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assert(proc_self_mountinfo);
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/* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already
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/* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already
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@ -134,11 +157,11 @@ int bind_remount_recursive_with_mountinfo(
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* If the "blacklist" parameter is specified it may contain a list of subtrees to exclude from the
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* If the "blacklist" parameter is specified it may contain a list of subtrees to exclude from the
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* remount operation. Note that we'll ignore the blacklist for the top-level path. */
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* remount operation. Note that we'll ignore the blacklist for the top-level path. */
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cleaned = strdup(prefix);
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simplified = strdup(prefix);
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if (!cleaned)
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if (!simplified)
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return -ENOMEM;
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return -ENOMEM;
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path_simplify(cleaned, false);
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path_simplify(simplified, false);
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done = set_new(&path_hash_ops);
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done = set_new(&path_hash_ops);
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if (!done)
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if (!done)
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@ -177,26 +200,26 @@ int bind_remount_recursive_with_mountinfo(
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if (!path || !type)
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if (!path || !type)
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continue;
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continue;
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if (!path_startswith(path, cleaned))
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if (!path_startswith(path, simplified))
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continue;
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continue;
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/* Ignore this mount if it is blacklisted, but only if it isn't the top-level mount
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/* Ignore this mount if it is blacklisted, but only if it isn't the top-level mount
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* we shall operate on. */
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* we shall operate on. */
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if (!path_equal(path, cleaned)) {
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if (!path_equal(path, simplified)) {
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bool blacklisted = false;
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bool blacklisted = false;
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char **i;
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char **i;
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STRV_FOREACH(i, blacklist) {
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STRV_FOREACH(i, blacklist) {
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if (path_equal(*i, cleaned))
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if (path_equal(*i, simplified))
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continue;
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continue;
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if (!path_startswith(*i, cleaned))
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if (!path_startswith(*i, simplified))
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continue;
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continue;
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if (path_startswith(path, *i)) {
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if (path_startswith(path, *i)) {
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blacklisted = true;
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blacklisted = true;
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log_debug("Not remounting %s blacklisted by %s, called for %s",
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log_debug("Not remounting %s blacklisted by %s, called for %s",
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path, *i, cleaned);
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path, *i, simplified);
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break;
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break;
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}
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}
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}
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}
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@ -211,7 +234,7 @@ int bind_remount_recursive_with_mountinfo(
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* already triggered, then we will find
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* already triggered, then we will find
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* another entry for this. */
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* another entry for this. */
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if (streq(type, "autofs")) {
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if (streq(type, "autofs")) {
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top_autofs = top_autofs || path_equal(path, cleaned);
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top_autofs = top_autofs || path_equal(path, simplified);
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continue;
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continue;
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}
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}
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@ -226,25 +249,24 @@ int bind_remount_recursive_with_mountinfo(
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* the root is either already done, or an autofs, we
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* the root is either already done, or an autofs, we
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* are done */
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* are done */
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if (set_isempty(todo) &&
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if (set_isempty(todo) &&
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(top_autofs || set_contains(done, cleaned)))
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(top_autofs || set_contains(done, simplified)))
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return 0;
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return 0;
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if (!set_contains(done, cleaned) &&
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if (!set_contains(done, simplified) &&
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!set_contains(todo, cleaned)) {
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!set_contains(todo, simplified)) {
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/* The prefix directory itself is not yet a mount, make it one. */
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/* The prefix directory itself is not yet a mount, make it one. */
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if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
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if (mount(simplified, simplified, NULL, MS_BIND|MS_REC, NULL) < 0)
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return -errno;
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return -errno;
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orig_flags = 0;
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orig_flags = 0;
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(void) get_mount_flags(cleaned, &orig_flags, table);
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(void) get_mount_flags(table, simplified, &orig_flags);
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orig_flags &= ~MS_RDONLY;
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if (mount(NULL, cleaned, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL) < 0)
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if (mount(NULL, simplified, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL) < 0)
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return -errno;
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return -errno;
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log_debug("Made top-level directory %s a mount point.", prefix);
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log_debug("Made top-level directory %s a mount point.", prefix);
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r = set_put_strdup(done, cleaned);
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r = set_put_strdup(done, simplified);
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if (r < 0)
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if (r < 0)
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return r;
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return r;
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}
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}
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@ -278,8 +300,7 @@ int bind_remount_recursive_with_mountinfo(
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/* Try to reuse the original flag set */
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/* Try to reuse the original flag set */
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orig_flags = 0;
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orig_flags = 0;
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(void) get_mount_flags(x, &orig_flags, table);
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(void) get_mount_flags(table, x, &orig_flags);
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orig_flags &= ~MS_RDONLY;
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if (mount(NULL, x, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL) < 0)
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if (mount(NULL, x, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL) < 0)
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return -errno;
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return -errno;
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@ -289,7 +310,12 @@ int bind_remount_recursive_with_mountinfo(
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}
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}
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}
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}
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int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **blacklist) {
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int bind_remount_recursive(
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const char *prefix,
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unsigned long new_flags,
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unsigned long flags_mask,
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char **blacklist) {
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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int r;
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int r;
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@ -300,6 +326,38 @@ int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned
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return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, blacklist, proc_self_mountinfo);
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return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, blacklist, proc_self_mountinfo);
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}
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}
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int bind_remount_one_with_mountinfo(
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const char *path,
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unsigned long new_flags,
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unsigned long flags_mask,
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FILE *proc_self_mountinfo) {
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_cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL;
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unsigned long orig_flags = 0;
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int r;
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assert(path);
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assert(proc_self_mountinfo);
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rewind(proc_self_mountinfo);
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table = mnt_new_table();
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if (!table)
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return -ENOMEM;
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r = mnt_table_parse_stream(table, proc_self_mountinfo, "/proc/self/mountinfo");
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if (r < 0)
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return r;
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/* Try to reuse the original flag set */
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(void) get_mount_flags(table, path, &orig_flags);
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if (mount(NULL, path, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL) < 0)
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return -errno;
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return 0;
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}
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int mount_move_root(const char *path) {
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int mount_move_root(const char *path) {
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assert(path);
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assert(path);
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@ -10,6 +10,7 @@ int repeat_unmount(const char *path, int flags);
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int umount_recursive(const char *target, int flags);
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int umount_recursive(const char *target, int flags);
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int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **blacklist);
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int bind_remount_recursive(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **blacklist);
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int bind_remount_recursive_with_mountinfo(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **blacklist, FILE *proc_self_mountinfo);
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int bind_remount_recursive_with_mountinfo(const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **blacklist, FILE *proc_self_mountinfo);
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int bind_remount_one_with_mountinfo(const char *path, unsigned long new_flags, unsigned long flags_mask, FILE *proc_self_mountinfo);
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int mount_move_root(const char *path);
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int mount_move_root(const char *path);
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