netdev - Re: [PATCH net] net/tls(TLS_SW): Fix integrity issue with non-blocking sw KTLS request

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Message-ID: <20200518155016.75be3663@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 18 May 2020 15:50:16 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Pooja Trivedi <poojatrivedi@...il.com>
Cc:     borisp@...lanox.com, aviadye@...lanox.com,
        john.fastabend@...il.com, daniel@...earbox.net,
        davem@...emloft.net, vakul.garg@....com, netdev@...r.kernel.org,
        linux-crypto@...r.kernel.org,
        mallesham.jatharkonda@...convergence.com, josh.tway@...ckpath.com,
        pooja.trivedi@...ckpath.com
Subject: Re: [PATCH net] net/tls(TLS_SW): Fix integrity issue with
 non-blocking sw KTLS request

On Sun, 17 May 2020 16:26:36 +0000 Pooja Trivedi wrote:
> In pure sw ktls(AES-NI), -EAGAIN from tcp layer (do_tcp_sendpages for
> encrypted record) gets treated as error, subtracts the offset, and
> returns to application. Because of this, application sends data from
> subtracted offset, which leads to data integrity issue. Since record is
> already encrypted, ktls module marks it as partially sent and pushes the
> packet to tcp layer in the following iterations (either from bottom half
> or when pushing next chunk). So returning success in case of EAGAIN
> will fix the issue.
> 
> Fixes: a42055e8d2c3 ("net/tls: Add support for async encryption")
> Signed-off-by: Pooja Trivedi <pooja.trivedi@...ckpath.com>
> Reviewed-by: Mallesham Jatharkonda <mallesham.jatharkonda@...convergence.com>
> Reviewed-by: Josh Tway <josh.tway@...ckpath.com>

This looks reasonable, I think. Next time user space calls if no new
buffer space was made available it will get a -EAGAIN, right?

Two questions - is there any particular application or use case that
runs into this? Seems a bit surprising to see a patch from Vadim and
you guys come at the same time.

Could you also add test for this bug? 
In tools/testing/selftests/net/tls.c