linux-kernel - Re: [PATCH 1/2] fscrypt: new helper function

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ZA9mwPUg7H/fq0L8@sol.localdomain>
Date:   Mon, 13 Mar 2023 11:09:04 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Luís Henriques <lhenriques@...e.de>
Cc:     Xiubo Li <xiubli@...hat.com>, Jeff Layton <jlayton@...nel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        linux-fscrypt@...r.kernel.org, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] fscrypt: new helper function -
 fscrypt_prepare_atomic_open()

On Mon, Mar 13, 2023 at 12:33:09PM +0000, Luís Henriques wrote:
> + * The regular open path will use fscrypt_file_open for that, but in the
> + * atomic open a different approach is required.

This should actually be fscrypt_prepare_lookup, not fscrypt_file_open, right?

> +int fscrypt_prepare_atomic_open(struct inode *dir, struct dentry *dentry)
> +{
> +	int err;
> +
> +	if (!IS_ENCRYPTED(dir))
> +		return 0;
> +
> +	err = fscrypt_get_encryption_info(dir, true);
> +	if (!err && !fscrypt_has_encryption_key(dir)) {
> +		spin_lock(&dentry->d_lock);
> +		dentry->d_flags |= DCACHE_NOKEY_NAME;
> +		spin_unlock(&dentry->d_lock);
> +	}
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(fscrypt_prepare_atomic_open);
[...]
> +static inline int fscrypt_prepare_atomic_open(struct inode *dir,
> +					      struct dentry *dentry)
> +{
> +	return -EOPNOTSUPP;
> +}

This has different behavior on unencrypted directories depending on whether
CONFIG_FS_ENCRYPTION is enabled or not.  That's bad.

In patch 2, the caller you are introducing has already checked IS_ENCRYPTED().

Also, your kerneldoc comment for fscrypt_prepare_atomic_open() says it is for
*encrypted* directories.

So IMO, just remove the IS_ENCRYPTED() check from the CONFIG_FS_ENCRYPTION
version of fscrypt_prepare_atomic_open().

- Eric