linux-kernel - Re: [PATCH v2] nvmet-auth: update sc

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Message-ID: <20251105132023.GC19044@lst.de>
Date: Wed, 5 Nov 2025 14:20:24 +0100
From: Christoph Hellwig <hch@....de>
To: alistair23@...il.com
Cc: hare@...e.de, kbusch@...nel.org, axboe@...nel.dk, hch@....de,
	sagi@...mberg.me, kch@...dia.com, linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Alistair Francis <alistair.francis@....com>
Subject: Re: [PATCH v2] nvmet-auth: update sc_c in target host hash
 calculation

>  4 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/auth.c b/drivers/nvme/host/auth.c
> index a01178caf15b..19980122d3d5 100644
> --- a/drivers/nvme/host/auth.c
> +++ b/drivers/nvme/host/auth.c
> @@ -492,6 +492,7 @@ static int nvme_auth_dhchap_setup_host_response(struct nvme_ctrl *ctrl,
>  	ret = crypto_shash_update(shash, buf, 2);
>  	if (ret)
>  		goto out;
> +	memset(buf, 0, sizeof(buf));
>  	*buf = chap->sc_c;
>  	ret = crypto_shash_update(shash, buf, 1);

I'm really confused about both the existing code and this fixup.

Why isn't chap->sc_c directly passed to crypto_shash_update here?
Why do we need to memset buf when only a single byte is passed to
crypto_shash_update?

>  	ret = crypto_shash_update(shash, buf, 2);
>  	if (ret)
>  		goto out;
> -	*buf = sc_c;
> +	*buf = req->sq->sc_c;
>  	ret = crypto_shash_update(shash, buf, 1);

Just pass it directly here?

>  	if (ret)
>  		goto out;
> @@ -378,6 +378,7 @@ int nvmet_auth_host_hash(struct nvmet_req *req, u8 *response,
>  	ret = crypto_shash_update(shash, ctrl->hostnqn, strlen(ctrl->hostnqn));
>  	if (ret)
>  		goto out;
> +	memset(buf, 0, sizeof(buf));
>  	ret = crypto_shash_update(shash, buf, 1);

just have a

	sttic const u8 zero = 0;

and use that here instead of the memset?