Re: [PATCH] fscrypt: to make sure the inode->i_blkbits is correctly set

[Eric Biggers]

On Thu, Jan 25, 2024 at 12:48:25PM +0800, xiubli@xxxxxxxxxx wrote:
> From: Xiubo Li <xiubli@xxxxxxxxxx>
> 
> The inode->i_blkbits should be already set before calling
> fscrypt_get_encryption_info() and it will be used this to setup the
> ci_data_unit_bits.
> 
> Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> ---
>  fs/crypto/keysetup.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
> index d71f7c799e79..909187e52bae 100644
> --- a/fs/crypto/keysetup.c
> +++ b/fs/crypto/keysetup.c
> @@ -702,6 +702,9 @@ int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
>  /**
>   * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
>   * @dir: a possibly-encrypted directory
>   * @inode: the new inode.  ->i_mode must be set already.
>   *         ->i_ino doesn't need to be set yet.

Maybe just change the above to "->i_mode and ->i_blkbits", instead of adding a
separate paragraph?

>   * @encrypt_ret: (output) set to %true if the new inode will be encrypted
>   *
>   * If the directory is encrypted, set up its ->i_crypt_info in preparation for
>   * encrypting the name of the new file.  Also, if the new inode will be
>   * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
>   *
>   * This isn't %GFP_NOFS-safe, and therefore it should be called before starting
>   * any filesystem transaction to create the inode.  For this reason, ->i_ino
>   * isn't required to be set yet, as the filesystem may not have set it yet.
>   *
>   * This doesn't persist the new inode's encryption context.  That still needs to
>   * be done later by calling fscrypt_set_context().
>   *
> + * Please note that the inode->i_blkbits should be already set before calling
> + * this and later it will be used to setup the ci_data_unit_bits.
> + *
>   * Return: 0 on success, -ENOKEY if the encryption key is missing, or another
>   *	   -errno code
>   */
> @@ -717,6 +720,9 @@ int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
>  	if (IS_ERR(policy))
>  		return PTR_ERR(policy);
>  
> +	if (WARN_ON_ONCE(inode->i_blkbits == 0))
> +		return -EINVAL;
> +

Thanks,

- Eric