linux-kernel - Re: [PATCH] cifs: Fix problem with encrypted RDMA data read

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Message-ID: <2147870.1668582019@warthog.procyon.org.uk>
Date:   Wed, 16 Nov 2022 07:00:19 +0000
From:   David Howells <dhowells@...hat.com>
To:     Stefan Metzmacher <metze@...ba.org>
Cc:     dhowells@...hat.com, smfrench@...il.com, tom@...pey.com,
        Long Li <longli@...rosoft.com>,
        Namjae Jeon <linkinjeon@...nel.org>,
        linux-cifs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cifs: Fix problem with encrypted RDMA data read

Stefan Metzmacher <metze@...ba.org> wrote:

> I'm not sure I understand why this would fix anything when encryption is
> enabled.
> 
> Is the payload still be offloaded as plaintext? Otherwise we wouldn't have
> use_rdma_mr...  So this rather looks like a fix for the non encrypted case.

The "inline"[*] PDUs are encrypted, but the direct RDMA data transmission is
not.  I'm not sure if this is a bug in ksmbd.  As I understand it, encrypting
and decrypting the directly transferred data would need to be done by the NIC,
not the cifs driver.

David

[*] I don't know the correct RDMA terminology for these things.