Re: [PATCH] crypto: Drop unused cipher_null crypto_alg

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Apr 20, 2026 at 11:41:20AM +0200, Ard Biesheuvel wrote:
> The cipher_null crypto_alg cipher is never used in a meaningful way,
> given that it is always wrapped in ecb(), which has its own dedicated
> implementation. IOW, the cipher_null crypto_alg should never be used to
> implement the ecb(cipher_null) skcipher, and using it for other things
> is bogus.
> 
> However, it is accessible from user space, and due to the nature of the
> AF_ALG interface, it may be wrapped in arbitrary ways, exposing issues
> in template code that wasn't written with block ciphers with a block
> size of '1' in mind.
> 
> So drop this code.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  crypto/crypto_null.c | 35 ++------------------
>  1 file changed, 2 insertions(+), 33 deletions(-)

Reviewed-by: Eric Biggers <ebiggers@kernel.org>

- Eric