diff options
| -rw-r--r-- | fs/namespace.c | 148 |
1 files changed, 78 insertions, 70 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 0044feef59d0..627db2e031e9 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -563,12 +563,9 @@ int sb_prepare_remount_readonly(struct super_block *sb) lock_mount_hash(); list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { - mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; - smp_mb(); - if (mnt_get_writers(mnt) > 0) { - err = -EBUSY; + err = mnt_hold_writers(mnt); + if (err) break; - } } } if (!err && atomic_long_read(&sb->s_remove_count)) @@ -4000,46 +3997,57 @@ static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) return 0; } -static struct mount *mount_setattr_prepare(struct mount_kattr *kattr, - struct mount *mnt, int *err) +/** + * mnt_allow_writers() - check whether the attribute change allows writers + * @kattr: the new mount attributes + * @mnt: the mount to which @kattr will be applied + * + * Check whether thew new mount attributes in @kattr allow concurrent writers. + * + * Return: true if writers need to be held, false if not + */ +static inline bool mnt_allow_writers(const struct mount_kattr *kattr, + const struct mount *mnt) { - struct mount *m = mnt, *last = NULL; + return !(kattr->attr_set & MNT_READONLY) || + (mnt->mnt.mnt_flags & MNT_READONLY); +} - if (!is_mounted(&m->mnt)) { - *err = -EINVAL; - goto out; - } +static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt) +{ + struct mount *m; + int err; - if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) { - *err = -EINVAL; - goto out; - } + for (m = mnt; m; m = next_mnt(m, mnt)) { + if (!can_change_locked_flags(m, recalc_flags(kattr, m))) { + err = -EPERM; + break; + } - do { - unsigned int flags; + err = can_idmap_mount(kattr, m); + if (err) + break; - flags = recalc_flags(kattr, m); - if (!can_change_locked_flags(m, flags)) { - *err = -EPERM; - goto out; + if (!mnt_allow_writers(kattr, m)) { + err = mnt_hold_writers(m); + if (err) + break; } - *err = can_idmap_mount(kattr, m); - if (*err) - goto out; + if (!kattr->recurse) + return 0; + } - last = m; + if (err) { + struct mount *p; - if ((kattr->attr_set & MNT_READONLY) && - !(m->mnt.mnt_flags & MNT_READONLY)) { - *err = mnt_hold_writers(m); - if (*err) - goto out; + for (p = mnt; p != m; p = next_mnt(p, mnt)) { + /* If we had to hold writers unblock them. */ + if (p->mnt.mnt_flags & MNT_WRITE_HOLD) + mnt_unhold_writers(p); } - } while (kattr->recurse && (m = next_mnt(m, mnt))); - -out: - return last; + } + return err; } static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) @@ -4067,48 +4075,32 @@ static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) put_user_ns(old_mnt_userns); } -static void mount_setattr_commit(struct mount_kattr *kattr, - struct mount *mnt, struct mount *last, - int err) +static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt) { - struct mount *m = mnt; + struct mount *m; - do { - if (!err) { - unsigned int flags; + for (m = mnt; m; m = next_mnt(m, mnt)) { + unsigned int flags; - do_idmap_mount(kattr, m); - flags = recalc_flags(kattr, m); - WRITE_ONCE(m->mnt.mnt_flags, flags); - } + do_idmap_mount(kattr, m); + 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)) + /* If we had to hold writers unblock them. */ + if (m->mnt.mnt_flags & MNT_WRITE_HOLD) mnt_unhold_writers(m); - if (!err && kattr->propagation) + if (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) + if (!kattr->recurse) break; - } while (kattr->recurse && (m = next_mnt(m, mnt))); - - if (!err) - touch_mnt_namespace(mnt->mnt_ns); + } + 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; + struct mount *mnt = real_mount(path->mnt); int err = 0; if (path->dentry != mnt->mnt.mnt_root) @@ -4129,16 +4121,32 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) } } + err = -EINVAL; lock_mount_hash(); + /* Ensure that this isn't anything purely vfs internal. */ + if (!is_mounted(&mnt->mnt)) + goto out; + /* - * Get the mount tree in a shape where we can change mount - * properties without failure. + * If this is an attached mount make sure it's located in the callers + * mount namespace. If it's not don't let the caller interact with it. + * If this is a detached mount make sure it has an anonymous mount + * namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE. */ - 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); + if (!(mnt_has_parent(mnt) ? check_mnt(mnt) : is_anon_ns(mnt->mnt_ns))) + goto out; + + /* + * First, we get the mount tree in a shape where we can change mount + * properties without failure. If we succeeded to do so we commit all + * changes and if we failed we clean up. + */ + err = mount_setattr_prepare(kattr, mnt); + if (!err) + mount_setattr_commit(kattr, mnt); +out: unlock_mount_hash(); if (kattr->propagation) { |