[PATCH v4 15/46] btrfs: handle nokey names.

Josef Bacik
2023-12-01T22:12:15Z

From: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>

For encrypted or unencrypted names, we calculate the offset for the dir
item by hashing the name for the dir item. However, this doesn't work
for a long nokey name, where we do not have the complete ciphertext.
Instead, fscrypt stores the filesystem-provided hash in the nokey name,
and we can extract it from the fscrypt_name structure in such a case.

Additionally, for nokey names, if we find the nokey name on disk we can
update the fscrypt_name with the disk name, so add that to searching for
diritems.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/dir-item.c | 37 +++++++++++++++++++++++++++++++++++--
fs/btrfs/fscrypt.c | 27 +++++++++++++++++++++++++++
fs/btrfs/fscrypt.h | 11 +++++++++++
3 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index a64cfddff7f0..897fb5477369 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -231,6 +231,28 @@ struct btrfs_dir_item *btrfs_lookup_dir_item(struct btrfs_trans_handle *trans,
return di;
}

+/*
+ * If appropriate, populate the disk name for a fscrypt_name looked up without
+ * a key.
+ *
+ * @path: The path to the extent buffer in which the name was found.
+ * @di: The dir item corresponding.
+ * @fname: The fscrypt_name to perhaps populate.
+ *
+ * Returns: 0 if the name is already populated or the dir item doesn't exist
+ * or the name was successfully populated, else an error code.
+ */
+static int ensure_disk_name_from_dir_item(struct btrfs_path *path,
+ struct btrfs_dir_item *di,
+ struct fscrypt_name *name)
+{
+ if (name->disk_name.name || !di)
+ return 0;
+
+ return btrfs_fscrypt_get_disk_name(path->nodes[0], di,
+ &name->disk_name);
+}
+
/*
* Lookup for a directory item by fscrypt_name.
*
@@ -257,8 +279,12 @@ struct btrfs_dir_item *btrfs_lookup_dir_item_fname(struct btrfs_trans_handle *tr

key.objectid = dir;
key.type = BTRFS_DIR_ITEM_KEY;
- key.offset = btrfs_name_hash(name->disk_name.name, name->disk_name.len);
- /* XXX get the right hash for no-key names */
+
+ if (!name->disk_name.name)
+ key.offset = name->hash | ((u64)name->minor_hash << 32);
+ else
+ key.offset = btrfs_name_hash(name->disk_name.name,
+ name->disk_name.len);

ret = btrfs_search_slot(trans, root, &key, path, mod, -mod);
if (ret == 0)
@@ -266,6 +292,8 @@ struct btrfs_dir_item *btrfs_lookup_dir_item_fname(struct btrfs_trans_handle *tr

if (ret == -ENOENT || (di && IS_ERR(di) && PTR_ERR(di) == -ENOENT))
return NULL;
+ if (ret == 0)
+ ret = ensure_disk_name_from_dir_item(path, di, name);
if (ret < 0)
di = ERR_PTR(ret);

@@ -382,7 +410,12 @@ btrfs_search_dir_index_item(struct btrfs_root *root, struct btrfs_path *path,
btrfs_for_each_slot(root, &key, &key, path, ret) {
if (key.objectid != dirid || key.type != BTRFS_DIR_INDEX_KEY)
break;
+
di = btrfs_match_dir_item_fname(root->fs_info, path, name);
+ if (di)
+ ret = ensure_disk_name_from_dir_item(path, di, name);
+ if (ret)
+ break;
if (di)
return di;
}
diff --git a/fs/btrfs/fscrypt.c b/fs/btrfs/fscrypt.c
index 6a4e4f63a660..9103da28af7e 100644
--- a/fs/btrfs/fscrypt.c
+++ b/fs/btrfs/fscrypt.c
@@ -14,6 +14,33 @@
#include "transaction.h"
#include "xattr.h"

+/*
+ * From a given location in a leaf, read a name into a qstr (usually a
+ * fscrypt_name's disk_name), allocating the required buffer. Used for
+ * nokey names.
+ */
+int btrfs_fscrypt_get_disk_name(struct extent_buffer *leaf,
+ struct btrfs_dir_item *dir_item,
+ struct fscrypt_str *name)
+{
+ unsigned long de_name_len = btrfs_dir_name_len(leaf, dir_item);
+ unsigned long de_name = (unsigned long)(dir_item + 1);
+ /*
+ * For no-key names, we use this opportunity to find the disk
+ * name, so future searches don't need to deal with nokey names
+ * and we know what the encrypted size is.
+ */
+ name->name = kmalloc(de_name_len, GFP_NOFS);
+
+ if (!name->name)
+ return -ENOMEM;
+
+ read_extent_buffer(leaf, name->name, de_name, de_name_len);
+
+ name->len = de_name_len;
+ return 0;
+}
+
/*
* This function is extremely similar to fscrypt_match_name() but uses an
* extent_buffer.
diff --git a/fs/btrfs/fscrypt.h b/fs/btrfs/fscrypt.h
index 1647bbbcd609..c08fd52c99b4 100644
--- a/fs/btrfs/fscrypt.h
+++ b/fs/btrfs/fscrypt.h
@@ -9,11 +9,22 @@
#include "fs.h"

#ifdef CONFIG_FS_ENCRYPTION
+int btrfs_fscrypt_get_disk_name(struct extent_buffer *leaf,
+ struct btrfs_dir_item *di,
+ struct fscrypt_str *qstr);
+
bool btrfs_fscrypt_match_name(struct fscrypt_name *fname,
struct extent_buffer *leaf,
unsigned long de_name, u32 de_name_len);

#else
+static inline int btrfs_fscrypt_get_disk_name(struct extent_buffer *leaf,
+ struct btrfs_dir_item *di,
+ struct fscrypt_str *qstr)
+{
+ return 0;
+}
+
static inline bool btrfs_fscrypt_match_name(struct fscrypt_name *fname,
struct extent_buffer *leaf,
unsigned long de_name,
--
2.41.0