switch mnt_hash to hlist
fixes RCU bug - walking through hlist is safe in face of element moves, since it's self-terminating. Cyclic lists are not - if we end up jumping to another hash chain, we'll loop infinitely without ever hitting the original list head. [fix for dumb braino folded] Spotted by: Max Kellermann <mk@cm4all.com> Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
Родитель
0b1b901b5a
Коммит
38129a13e6
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@ -25,7 +25,7 @@ struct mountpoint {
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};
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struct mount {
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struct list_head mnt_hash;
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struct hlist_node mnt_hash;
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struct mount *mnt_parent;
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struct dentry *mnt_mountpoint;
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struct vfsmount mnt;
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@ -59,7 +59,7 @@ static DEFINE_SPINLOCK(mnt_id_lock);
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static int mnt_id_start = 0;
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static int mnt_group_start = 1;
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static struct list_head *mount_hashtable __read_mostly;
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static struct hlist_head *mount_hashtable __read_mostly;
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static struct hlist_head *mountpoint_hashtable __read_mostly;
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static struct kmem_cache *mnt_cache __read_mostly;
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static DECLARE_RWSEM(namespace_sem);
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@ -78,7 +78,7 @@ EXPORT_SYMBOL_GPL(fs_kobj);
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*/
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
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static inline struct list_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
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static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
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{
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unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
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tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
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@ -217,7 +217,7 @@ static struct mount *alloc_vfsmnt(const char *name)
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mnt->mnt_writers = 0;
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#endif
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INIT_LIST_HEAD(&mnt->mnt_hash);
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INIT_HLIST_NODE(&mnt->mnt_hash);
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INIT_LIST_HEAD(&mnt->mnt_child);
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INIT_LIST_HEAD(&mnt->mnt_mounts);
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INIT_LIST_HEAD(&mnt->mnt_list);
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@ -605,10 +605,10 @@ bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
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*/
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struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
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{
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struct list_head *head = m_hash(mnt, dentry);
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struct hlist_head *head = m_hash(mnt, dentry);
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struct mount *p;
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list_for_each_entry_rcu(p, head, mnt_hash)
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hlist_for_each_entry_rcu(p, head, mnt_hash)
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if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
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return p;
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return NULL;
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@ -620,20 +620,16 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
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*/
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struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
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{
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struct list_head *head = m_hash(mnt, dentry);
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struct mount *p, *res = NULL;
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list_for_each_entry(p, head, mnt_hash)
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if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
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goto found;
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return res;
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found:
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res = p;
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list_for_each_entry_continue(p, head, mnt_hash) {
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struct mount *p, *res;
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res = p = __lookup_mnt(mnt, dentry);
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if (!p)
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goto out;
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hlist_for_each_entry_continue(p, mnt_hash) {
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if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
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break;
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res = p;
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}
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out:
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return res;
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}
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@ -750,7 +746,7 @@ static void detach_mnt(struct mount *mnt, struct path *old_path)
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mnt->mnt_parent = mnt;
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mnt->mnt_mountpoint = mnt->mnt.mnt_root;
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list_del_init(&mnt->mnt_child);
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list_del_init(&mnt->mnt_hash);
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hlist_del_init_rcu(&mnt->mnt_hash);
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put_mountpoint(mnt->mnt_mp);
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mnt->mnt_mp = NULL;
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}
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@ -777,7 +773,7 @@ static void attach_mnt(struct mount *mnt,
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struct mountpoint *mp)
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{
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mnt_set_mountpoint(parent, mp, mnt);
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list_add(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
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hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
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list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
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}
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@ -800,9 +796,9 @@ static void commit_tree(struct mount *mnt, struct mount *shadows)
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list_splice(&head, n->list.prev);
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if (shadows)
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list_add(&mnt->mnt_hash, &shadows->mnt_hash);
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hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
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else
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list_add(&mnt->mnt_hash,
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hlist_add_head_rcu(&mnt->mnt_hash,
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m_hash(&parent->mnt, mnt->mnt_mountpoint));
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list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
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touch_mnt_namespace(n);
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@ -1193,26 +1189,28 @@ int may_umount(struct vfsmount *mnt)
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EXPORT_SYMBOL(may_umount);
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static LIST_HEAD(unmounted); /* protected by namespace_sem */
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static HLIST_HEAD(unmounted); /* protected by namespace_sem */
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static void namespace_unlock(void)
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{
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struct mount *mnt;
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LIST_HEAD(head);
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struct hlist_head head = unmounted;
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if (likely(list_empty(&unmounted))) {
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if (likely(hlist_empty(&head))) {
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up_write(&namespace_sem);
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return;
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}
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list_splice_init(&unmounted, &head);
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head.first->pprev = &head.first;
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INIT_HLIST_HEAD(&unmounted);
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up_write(&namespace_sem);
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synchronize_rcu();
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while (!list_empty(&head)) {
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mnt = list_first_entry(&head, struct mount, mnt_hash);
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list_del_init(&mnt->mnt_hash);
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while (!hlist_empty(&head)) {
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mnt = hlist_entry(head.first, struct mount, mnt_hash);
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hlist_del_init(&mnt->mnt_hash);
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if (mnt->mnt_ex_mountpoint.mnt)
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path_put(&mnt->mnt_ex_mountpoint);
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mntput(&mnt->mnt);
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@ -1233,16 +1231,19 @@ static inline void namespace_lock(void)
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*/
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void umount_tree(struct mount *mnt, int how)
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{
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LIST_HEAD(tmp_list);
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HLIST_HEAD(tmp_list);
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struct mount *p;
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struct mount *last = NULL;
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for (p = mnt; p; p = next_mnt(p, mnt))
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list_move(&p->mnt_hash, &tmp_list);
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for (p = mnt; p; p = next_mnt(p, mnt)) {
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hlist_del_init_rcu(&p->mnt_hash);
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hlist_add_head(&p->mnt_hash, &tmp_list);
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}
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if (how)
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propagate_umount(&tmp_list);
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list_for_each_entry(p, &tmp_list, mnt_hash) {
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hlist_for_each_entry(p, &tmp_list, mnt_hash) {
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list_del_init(&p->mnt_expire);
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list_del_init(&p->mnt_list);
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__touch_mnt_namespace(p->mnt_ns);
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@ -1260,8 +1261,13 @@ void umount_tree(struct mount *mnt, int how)
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p->mnt_mp = NULL;
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}
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change_mnt_propagation(p, MS_PRIVATE);
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last = p;
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}
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if (last) {
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last->mnt_hash.next = unmounted.first;
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unmounted.first = tmp_list.first;
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unmounted.first->pprev = &unmounted.first;
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}
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list_splice(&tmp_list, &unmounted);
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}
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static void shrink_submounts(struct mount *mnt);
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@ -1645,8 +1651,9 @@ static int attach_recursive_mnt(struct mount *source_mnt,
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struct mountpoint *dest_mp,
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struct path *parent_path)
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{
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LIST_HEAD(tree_list);
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HLIST_HEAD(tree_list);
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struct mount *child, *p;
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struct hlist_node *n;
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int err;
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if (IS_MNT_SHARED(dest_mnt)) {
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@ -1671,9 +1678,9 @@ static int attach_recursive_mnt(struct mount *source_mnt,
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commit_tree(source_mnt, NULL);
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}
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list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
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hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
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struct mount *q;
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list_del_init(&child->mnt_hash);
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hlist_del_init(&child->mnt_hash);
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q = __lookup_mnt_last(&child->mnt_parent->mnt,
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child->mnt_mountpoint);
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commit_tree(child, q);
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@ -2818,7 +2825,7 @@ void __init mnt_init(void)
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0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
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mount_hashtable = alloc_large_system_hash("Mount-cache",
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sizeof(struct list_head),
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sizeof(struct hlist_head),
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mhash_entries, 19,
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0,
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&m_hash_shift, &m_hash_mask, 0, 0);
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@ -2832,7 +2839,7 @@ void __init mnt_init(void)
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panic("Failed to allocate mount hash table\n");
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for (u = 0; u <= m_hash_mask; u++)
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INIT_LIST_HEAD(&mount_hashtable[u]);
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INIT_HLIST_HEAD(&mount_hashtable[u]);
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for (u = 0; u <= mp_hash_mask; u++)
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INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
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26
fs/pnode.c
26
fs/pnode.c
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@ -220,14 +220,14 @@ static struct mount *get_source(struct mount *dest,
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* @tree_list : list of heads of trees to be attached.
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*/
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int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
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struct mount *source_mnt, struct list_head *tree_list)
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struct mount *source_mnt, struct hlist_head *tree_list)
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{
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struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
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struct mount *m, *child;
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int ret = 0;
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struct mount *prev_dest_mnt = dest_mnt;
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struct mount *prev_src_mnt = source_mnt;
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LIST_HEAD(tmp_list);
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HLIST_HEAD(tmp_list);
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for (m = propagation_next(dest_mnt, dest_mnt); m;
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m = propagation_next(m, dest_mnt)) {
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@ -246,27 +246,29 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
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child = copy_tree(source, source->mnt.mnt_root, type);
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if (IS_ERR(child)) {
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ret = PTR_ERR(child);
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list_splice(tree_list, tmp_list.prev);
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tmp_list = *tree_list;
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tmp_list.first->pprev = &tmp_list.first;
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INIT_HLIST_HEAD(tree_list);
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goto out;
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}
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if (is_subdir(dest_mp->m_dentry, m->mnt.mnt_root)) {
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mnt_set_mountpoint(m, dest_mp, child);
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list_add_tail(&child->mnt_hash, tree_list);
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hlist_add_head(&child->mnt_hash, tree_list);
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} else {
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/*
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* This can happen if the parent mount was bind mounted
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* on some subdirectory of a shared/slave mount.
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*/
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list_add_tail(&child->mnt_hash, &tmp_list);
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hlist_add_head(&child->mnt_hash, &tmp_list);
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}
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prev_dest_mnt = m;
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prev_src_mnt = child;
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}
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out:
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lock_mount_hash();
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while (!list_empty(&tmp_list)) {
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child = list_first_entry(&tmp_list, struct mount, mnt_hash);
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while (!hlist_empty(&tmp_list)) {
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child = hlist_entry(tmp_list.first, struct mount, mnt_hash);
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umount_tree(child, 0);
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}
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unlock_mount_hash();
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@ -338,8 +340,10 @@ static void __propagate_umount(struct mount *mnt)
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* umount the child only if the child has no
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* other children
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*/
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if (child && list_empty(&child->mnt_mounts))
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list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
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if (child && list_empty(&child->mnt_mounts)) {
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hlist_del_init_rcu(&child->mnt_hash);
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hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
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}
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}
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}
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@ -350,11 +354,11 @@ static void __propagate_umount(struct mount *mnt)
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*
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* vfsmount lock must be held for write
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*/
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int propagate_umount(struct list_head *list)
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int propagate_umount(struct hlist_head *list)
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{
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struct mount *mnt;
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list_for_each_entry(mnt, list, mnt_hash)
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hlist_for_each_entry(mnt, list, mnt_hash)
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__propagate_umount(mnt);
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return 0;
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}
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@ -36,8 +36,8 @@ static inline void set_mnt_shared(struct mount *mnt)
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void change_mnt_propagation(struct mount *, int);
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int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
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struct list_head *);
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int propagate_umount(struct list_head *);
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struct hlist_head *);
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int propagate_umount(struct hlist_head *);
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int propagate_mount_busy(struct mount *, int);
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void mnt_release_group_id(struct mount *);
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int get_dominating_id(struct mount *mnt, const struct path *root);
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