[PATCH 3/6] ubifs: Fix unlink code wrt. double hash lookups

[Richard Weinberger]

When removing an encrypted file with a long name and without having
the key we have to be able to locate and remove the directory entry
via a double hash. This corner case was simply forgotten.

Fixes: 528e3d178f25 ("ubifs: Add full hash lookup support")
Reported-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
 fs/ubifs/journal.c |  10 ++++-
 fs/ubifs/tnc.c     | 129 ++++++++++++++++++++++++++++++++++++++++++++---------
 fs/ubifs/ubifs.h   |   2 +
 3 files changed, 117 insertions(+), 24 deletions(-)

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index f3b620cbdda4..7aef413ea2a9 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -585,7 +585,10 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
 
 	if (!xent) {
 		dent->ch.node_type = UBIFS_DENT_NODE;
-		dent_key_init(c, &dent_key, dir->i_ino, nm);
+		if (nm->hash)
+			dent_key_init_hash(c, &dent_key, dir->i_ino, nm->hash);
+		else
+			dent_key_init(c, &dent_key, dir->i_ino, nm);
 	} else {
 		dent->ch.node_type = UBIFS_XENT_NODE;
 		xent_key_init(c, &dent_key, dir->i_ino, nm);
@@ -629,7 +632,10 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct inode *dir,
 	kfree(dent);
 
 	if (deletion) {
-		err = ubifs_tnc_remove_nm(c, &dent_key, nm);
+		if (nm->hash)
+			err = ubifs_tnc_remove_dh(c, &dent_key, nm->minor_hash);
+		else
+			err = ubifs_tnc_remove_nm(c, &dent_key, nm);
 		if (err)
 			goto out_ro;
 		err = ubifs_add_dirt(c, lnum, dlen);
diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 709aa098dd46..b4526925fd78 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -1880,48 +1880,65 @@ int ubifs_tnc_lookup_nm(struct ubifs_info *c, const union ubifs_key *key,
 	return do_lookup_nm(c, key, node, nm);
 }
 
-static int do_lookup_dh(struct ubifs_info *c, const union ubifs_key *key,
-			struct ubifs_dent_node *dent, uint32_t cookie)
+static int search_dh_cookie(struct ubifs_info *c, const union ubifs_key *key,
+			    struct ubifs_dent_node *dent, uint32_t cookie,
+			    struct ubifs_znode **zn, int *n)
 {
-	int n, err, type = key_type(c, key);
-	struct ubifs_znode *znode;
+	int err;
+	struct ubifs_znode *znode = *zn;
 	struct ubifs_zbranch *zbr;
-	union ubifs_key *dkey, start_key;
-
-	ubifs_assert(is_hash_key(c, key));
-
-	lowest_dent_key(c, &start_key, key_inum(c, key));
-
-	mutex_lock(&c->tnc_mutex);
-	err = ubifs_lookup_level0(c, &start_key, &znode, &n);
-	if (unlikely(err < 0))
-		goto out_unlock;
+	union ubifs_key *dkey;
 
 	for (;;) {
 		if (!err) {
-			err = tnc_next(c, &znode, &n);
+			err = tnc_next(c, &znode, n);
 			if (err)
-				goto out_unlock;
+				goto out;
 		}
 
-		zbr = &znode->zbranch[n];
+		zbr = &znode->zbranch[*n];
 		dkey = &zbr->key;
 
 		if (key_inum(c, dkey) != key_inum(c, key) ||
-		    key_type(c, dkey) != type) {
+		    key_type(c, dkey) != key_type(c, key)) {
 			err = -ENOENT;
-			goto out_unlock;
+			goto out;
 		}
 
 		err = tnc_read_hashed_node(c, zbr, dent);
 		if (err)
-			goto out_unlock;
+			goto out;
 
 		if (key_hash(c, key) == key_hash(c, dkey) &&
-		    le32_to_cpu(dent->cookie) == cookie)
-			goto out_unlock;
+		    le32_to_cpu(dent->cookie) == cookie) {
+			*zn = znode;
+			goto out;
+		}
 	}
 
+out:
+
+	return err;
+}
+
+static int do_lookup_dh(struct ubifs_info *c, const union ubifs_key *key,
+			struct ubifs_dent_node *dent, uint32_t cookie)
+{
+	int n, err;
+	struct ubifs_znode *znode;
+	union ubifs_key start_key;
+
+	ubifs_assert(is_hash_key(c, key));
+
+	lowest_dent_key(c, &start_key, key_inum(c, key));
+
+	mutex_lock(&c->tnc_mutex);
+	err = ubifs_lookup_level0(c, &start_key, &znode, &n);
+	if (unlikely(err < 0))
+		goto out_unlock;
+
+	err = search_dh_cookie(c, key, dent, cookie, &znode, &n);
+
 out_unlock:
 	mutex_unlock(&c->tnc_mutex);
 	return err;
@@ -2663,6 +2680,74 @@ int ubifs_tnc_remove_nm(struct ubifs_info *c, const union ubifs_key *key,
 }
 
 /**
+ * ubifs_tnc_remove_dh - remove an index entry for a "double hashed" node.
+ * @c: UBIFS file-system description object
+ * @key: key of node
+ * @cookie: node cookie for collision resolution
+ *
+ * Returns %0 on success or negative error code on failure.
+ */
+int ubifs_tnc_remove_dh(struct ubifs_info *c, const union ubifs_key *key,
+			uint32_t cookie)
+{
+	int n, err;
+	struct ubifs_znode *znode;
+	struct ubifs_dent_node *dent;
+	struct ubifs_zbranch *zbr;
+
+	if (!c->double_hash)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&c->tnc_mutex);
+	err = lookup_level0_dirty(c, key, &znode, &n);
+	if (err <= 0)
+		goto out_unlock;
+
+	zbr = &znode->zbranch[n];
+	dent = kmalloc(UBIFS_MAX_DENT_NODE_SZ, GFP_NOFS);
+	if (!dent) {
+		err = -ENOMEM;
+		goto out_unlock;
+	}
+
+	err = tnc_read_hashed_node(c, zbr, dent);
+	if (err)
+		goto out_free;
+
+	/* If the cookie does not match, we're facing a hash collision. */
+	if (le32_to_cpu(dent->cookie) != cookie) {
+		union ubifs_key start_key;
+
+		lowest_dent_key(c, &start_key, key_inum(c, key));
+
+		err = ubifs_lookup_level0(c, &start_key, &znode, &n);
+		if (unlikely(err < 0))
+			goto out_free;
+
+		err = search_dh_cookie(c, key, dent, cookie, &znode, &n);
+		if (err)
+			goto out_free;
+	}
+
+	if (znode->cnext || !ubifs_zn_dirty(znode)) {
+		znode = dirty_cow_bottom_up(c, znode);
+		if (IS_ERR(znode)) {
+			err = PTR_ERR(znode);
+			goto out_free;
+		}
+	}
+	err = tnc_delete(c, znode, n);
+
+out_free:
+	kfree(dent);
+out_unlock:
+	if (!err)
+		err = dbg_check_tnc(c, 0);
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
  * key_in_range - determine if a key falls within a range of keys.
  * @c: UBIFS file-system description object
  * @key: key to check
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 298b4d89eee9..35338f0fa4e6 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1590,6 +1590,8 @@ int ubifs_tnc_add_nm(struct ubifs_info *c, const union ubifs_key *key,
 int ubifs_tnc_remove(struct ubifs_info *c, const union ubifs_key *key);
 int ubifs_tnc_remove_nm(struct ubifs_info *c, const union ubifs_key *key,
 			const struct fscrypt_name *nm);
+int ubifs_tnc_remove_dh(struct ubifs_info *c, const union ubifs_key *key,
+			uint32_t cookie);
 int ubifs_tnc_remove_range(struct ubifs_info *c, union ubifs_key *from_key,
 			   union ubifs_key *to_key);
 int ubifs_tnc_remove_ino(struct ubifs_info *c, ino_t inum);
-- 
2.12.0