Re: [PATCH v8 8/8] f2fs: Handle casefolding with Encryption

Eric Biggers
2020-03-07T05:24:28Z

On Fri, Mar 06, 2020 at 06:36:11PM -0800, Daniel Rosenberg wrote:
> int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
> const struct qstr *orig_name,
> + f2fs_hash_t dentry_hash,
> struct inode *inode, nid_t ino, umode_t mode)
> {
> unsigned int bit_pos;
> unsigned int level;
> unsigned int current_depth;
> unsigned long bidx, block;
> - f2fs_hash_t dentry_hash;
> unsigned int nbucket, nblock;
> struct page *dentry_page = NULL;
> struct f2fs_dentry_block *dentry_blk = NULL;
> @@ -632,7 +650,6 @@ int f2fs_add_regular_entry(struct inode *dir, const struct qstr *new_name,
>
> level = 0;
> slots = GET_DENTRY_SLOTS(new_name->len);
> - dentry_hash = f2fs_dentry_hash(dir, new_name, NULL);
>
> current_depth = F2FS_I(dir)->i_current_depth;
> if (F2FS_I(dir)->chash == dentry_hash) {
> @@ -718,17 +735,19 @@ int f2fs_add_dentry(struct inode *dir, struct fscrypt_name *fname,
> struct inode *inode, nid_t ino, umode_t mode)
> {
> struct qstr new_name;
> + f2fs_hash_t dentry_hash;
> int err = -EAGAIN;
>
> new_name.name = fname_name(fname);
> new_name.len = fname_len(fname);
>
> if (f2fs_has_inline_dentry(dir))
> - err = f2fs_add_inline_entry(dir, &new_name, fname->usr_fname,
> + err = f2fs_add_inline_entry(dir, &new_name, fname,
> inode, ino, mode);
> + dentry_hash = f2fs_dentry_hash(dir, &new_name, fname);
> if (err == -EAGAIN)
> err = f2fs_add_regular_entry(dir, &new_name, fname->usr_fname,
> - inode, ino, mode);
> + dentry_hash, inode, ino, mode);
>

Why are the changes to f2fs_add_dentry(), f2fs_add_regular_entry(), and
f2fs_add_inline_entry() being made? Directories can't be modified through
no-key names, so there's no need to make this part of the code handle grabbing
the dentry hash from the struct fscrypt_name. And both the on-disk and original
filenames were already passed to these functions. So what else do we need?

> +static f2fs_hash_t __f2fs_dentry_hash(const struct inode *dir,
> + const struct qstr *name_info,
> + const struct fscrypt_name *fname)
> {
> __u32 hash;
> f2fs_hash_t f2fs_hash;
> @@ -79,12 +80,17 @@ static f2fs_hash_t __f2fs_dentry_hash(const struct qstr *name_info,
> size_t len = name_info->len;
>
> /* encrypted bigname case */
> - if (fname && !fname->disk_name.name)
> + if (fname && !fname->is_ciphertext_name)
> return cpu_to_le32(fname->hash);

Isn't this check backwards? The hash is valid if fname->is_ciphertext_name, not
if !fname->is_ciphertext_name.

(Maybe the phrase "ciphertext name" is causing confusion, as we're now calling
them "no-key names" instead? We could rename it, if that would help.)

- Eric