Re: [PATCH] crypto: mxs-dcp: handle zero-length skcipher requests

[Frank Li]

On Fri, Aug 28, 2026 at 05:32:09PM +0800, Linmao Li wrote:
> [You don't often get email from lilinmao@xxxxxxxxxx. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>
> Zero-length skcipher requests are valid no-ops, but MXS-DCP queues them.

Any document show it? if return 0 when cryptelen, it is async, no
call crypto_request_complete.

Frank

> When such a request reaches the worker, last_out_len remains zero. The
> CBC completion path then subtracts AES_BLOCK_SIZE from this unsigned
> value when updating the IV, causing the offset to underflow. On
> decryption, the resulting source address precedes aes_in_buf.
>
> Return success before enqueueing zero-length requests. This avoids the
> invalid source access and leaves the IV unchanged for a no-op.
>
> Fixes: fadd7a6e616b ("crypto: mxs-dcp - Fix AES issues")
> Signed-off-by: Linmao Li <lilinmao@xxxxxxxxxx>
> ---
>  drivers/crypto/mxs-dcp.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c
> index 133ebc998236..60794b4d49fa 100644
> --- a/drivers/crypto/mxs-dcp.c
> +++ b/drivers/crypto/mxs-dcp.c
> @@ -473,6 +473,9 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb)
>         struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
>         int ret;
>
> +       if (!req->cryptlen)
> +               return 0;
> +
>         if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->key_referenced))
>                 return mxs_dcp_block_fallback(req, enc);
>
>
> base-commit: 8d3ae59288f1e7d58d76558a6ee96d533bc5019f
> --
> 2.25.1
>
>