static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
+struct mount_kattr {
+ unsigned int attr_set;
+ unsigned int attr_clr;
+ unsigned int propagation;
+ unsigned int lookup_flags;
+ bool recurse;
+};
+
/* /sys/fs */
struct kobject *fs_kobj;
EXPORT_SYMBOL_GPL(fs_kobj);
(MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME)
+#define MOUNT_SETATTR_VALID_FLAGS FSMOUNT_VALID_FLAGS
+
+#define MOUNT_SETATTR_PROPAGATION_FLAGS \
+ (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
+
static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
{
unsigned int mnt_flags = 0;
return error;
}
+static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
+{
+ unsigned int flags = mnt->mnt.mnt_flags;
+
+ /* flags to clear */
+ flags &= ~kattr->attr_clr;
+ /* flags to raise */
+ flags |= kattr->attr_set;
+
+ return flags;
+}
+
+static struct mount *mount_setattr_prepare(struct mount_kattr *kattr,
+ struct mount *mnt, int *err)
+{
+ struct mount *m = mnt, *last = NULL;
+
+ if (!is_mounted(&m->mnt)) {
+ *err = -EINVAL;
+ goto out;
+ }
+
+ if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) {
+ *err = -EINVAL;
+ goto out;
+ }
+
+ do {
+ unsigned int flags;
+
+ flags = recalc_flags(kattr, m);
+ if (!can_change_locked_flags(m, flags)) {
+ *err = -EPERM;
+ goto out;
+ }
+
+ last = m;
+
+ if ((kattr->attr_set & MNT_READONLY) &&
+ !(m->mnt.mnt_flags & MNT_READONLY)) {
+ *err = mnt_hold_writers(m);
+ if (*err)
+ goto out;
+ }
+ } while (kattr->recurse && (m = next_mnt(m, mnt)));
+
+out:
+ return last;
+}
+
+static void mount_setattr_commit(struct mount_kattr *kattr,
+ struct mount *mnt, struct mount *last,
+ int err)
+{
+ struct mount *m = mnt;
+
+ do {
+ if (!err) {
+ unsigned int flags;
+
+ flags = recalc_flags(kattr, m);
+ WRITE_ONCE(m->mnt.mnt_flags, flags);
+ }
+
+ /*
+ * We either set MNT_READONLY above so make it visible
+ * before ~MNT_WRITE_HOLD or we failed to recursively
+ * apply mount options.
+ */
+ if ((kattr->attr_set & MNT_READONLY) &&
+ (m->mnt.mnt_flags & MNT_WRITE_HOLD))
+ mnt_unhold_writers(m);
+
+ if (!err && kattr->propagation)
+ change_mnt_propagation(m, kattr->propagation);
+
+ /*
+ * On failure, only cleanup until we found the first mount
+ * we failed to handle.
+ */
+ if (err && m == last)
+ break;
+ } while (kattr->recurse && (m = next_mnt(m, mnt)));
+
+ if (!err)
+ touch_mnt_namespace(mnt->mnt_ns);
+}
+
+static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
+{
+ struct mount *mnt = real_mount(path->mnt), *last = NULL;
+ int err = 0;
+
+ if (path->dentry != mnt->mnt.mnt_root)
+ return -EINVAL;
+
+ if (kattr->propagation) {
+ /*
+ * Only take namespace_lock() if we're actually changing
+ * propagation.
+ */
+ namespace_lock();
+ if (kattr->propagation == MS_SHARED) {
+ err = invent_group_ids(mnt, kattr->recurse);
+ if (err) {
+ namespace_unlock();
+ return err;
+ }
+ }
+ }
+
+ lock_mount_hash();
+
+ /*
+ * Get the mount tree in a shape where we can change mount
+ * properties without failure.
+ */
+ last = mount_setattr_prepare(kattr, mnt, &err);
+ if (last) /* Commit all changes or revert to the old state. */
+ mount_setattr_commit(kattr, mnt, last, err);
+
+ unlock_mount_hash();
+
+ if (kattr->propagation) {
+ namespace_unlock();
+ if (err)
+ cleanup_group_ids(mnt, NULL);
+ }
+
+ return err;
+}
+
+static int build_mount_kattr(const struct mount_attr *attr,
+ struct mount_kattr *kattr, unsigned int flags)
+{
+ unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
+
+ if (flags & AT_NO_AUTOMOUNT)
+ lookup_flags &= ~LOOKUP_AUTOMOUNT;
+ if (flags & AT_SYMLINK_NOFOLLOW)
+ lookup_flags &= ~LOOKUP_FOLLOW;
+ if (flags & AT_EMPTY_PATH)
+ lookup_flags |= LOOKUP_EMPTY;
+
+ *kattr = (struct mount_kattr) {
+ .lookup_flags = lookup_flags,
+ .recurse = !!(flags & AT_RECURSIVE),
+ };
+
+ if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
+ return -EINVAL;
+ if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
+ return -EINVAL;
+ kattr->propagation = attr->propagation;
+
+ if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
+ return -EINVAL;
+
+ if (attr->userns_fd)
+ return -EINVAL;
+
+ kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
+ kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
+
+ /*
+ * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
+ * users wanting to transition to a different atime setting cannot
+ * simply specify the atime setting in @attr_set, but must also
+ * specify MOUNT_ATTR__ATIME in the @attr_clr field.
+ * So ensure that MOUNT_ATTR__ATIME can't be partially set in
+ * @attr_clr and that @attr_set can't have any atime bits set if
+ * MOUNT_ATTR__ATIME isn't set in @attr_clr.
+ */
+ if (attr->attr_clr & MOUNT_ATTR__ATIME) {
+ if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
+ return -EINVAL;
+
+ /*
+ * Clear all previous time settings as they are mutually
+ * exclusive.
+ */
+ kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
+ switch (attr->attr_set & MOUNT_ATTR__ATIME) {
+ case MOUNT_ATTR_RELATIME:
+ kattr->attr_set |= MNT_RELATIME;
+ break;
+ case MOUNT_ATTR_NOATIME:
+ kattr->attr_set |= MNT_NOATIME;
+ break;
+ case MOUNT_ATTR_STRICTATIME:
+ break;
+ default:
+ return -EINVAL;
+ }
+ } else {
+ if (attr->attr_set & MOUNT_ATTR__ATIME)
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
+ unsigned int, flags, struct mount_attr __user *, uattr,
+ size_t, usize)
+{
+ int err;
+ struct path target;
+ struct mount_attr attr;
+ struct mount_kattr kattr;
+
+ BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
+
+ if (flags & ~(AT_EMPTY_PATH |
+ AT_RECURSIVE |
+ AT_SYMLINK_NOFOLLOW |
+ AT_NO_AUTOMOUNT))
+ return -EINVAL;
+
+ if (unlikely(usize > PAGE_SIZE))
+ return -E2BIG;
+ if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
+ return -EINVAL;
+
+ if (!may_mount())
+ return -EPERM;
+
+ err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
+ if (err)
+ return err;
+
+ /* Don't bother walking through the mounts if this is a nop. */
+ if (attr.attr_set == 0 &&
+ attr.attr_clr == 0 &&
+ attr.propagation == 0)
+ return 0;
+
+ err = build_mount_kattr(&attr, &kattr, flags);
+ if (err)
+ return err;
+
+ err = user_path_at(dfd, path, kattr.lookup_flags, &target);
+ if (err)
+ return err;
+
+ err = do_mount_setattr(&target, &kattr);
+ path_put(&target);
+ return err;
+}
+
static void __init init_mount_tree(void)
{
struct vfsmount *mnt;
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