netdev - RE: [PATCH net 4/4] tls: Fix tls

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Date:   Wed, 27 Feb 2019 16:28:48 +0000
From:   Vakul Garg <vakul.garg@....com>
To:     Boris Pismenny <borisp@...lanox.com>,
        Dave Watson <davejwatson@...com>
CC:     Aviad Yehezkel <aviadye@...lanox.com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>
Subject: RE: [PATCH net 4/4] tls: Fix tls_device receive



> -----Original Message-----
> From: Boris Pismenny <borisp@...lanox.com>
> Sent: Wednesday, February 27, 2019 8:54 PM
> To: Vakul Garg <vakul.garg@....com>; Dave Watson
> <davejwatson@...com>
> Cc: Aviad Yehezkel <aviadye@...lanox.com>; john.fastabend@...il.com;
> daniel@...earbox.net; netdev@...r.kernel.org; Eran Ben Elisha
> <eranbe@...lanox.com>
> Subject: Re: [PATCH net 4/4] tls: Fix tls_device receive
> 
> 
> 
> On 2/27/2019 5:08 AM, Vakul Garg wrote:
> >
> >
> >> -----Original Message-----
> >> From: Dave Watson <davejwatson@...com>
> >> Sent: Wednesday, February 27, 2019 2:05 AM
> >> To: Boris Pismenny <borisp@...lanox.com>
> >> Cc: aviadye@...lanox.com; john.fastabend@...il.com;
> >> daniel@...earbox.net; Vakul Garg <vakul.garg@....com>;
> >> netdev@...r.kernel.org; eranbe@...lanox.com
> >> Subject: Re: [PATCH net 4/4] tls: Fix tls_device receive
> >>
> >> On 02/26/19 02:12 PM, Boris Pismenny wrote:
> >>> Currently, the receive function fails to handle records already
> >>> decrypted by the device due to the commit mentioned below.
> >>>
> >>> This commit advances the TLS record sequence number and prepares the
> >>> context to handle the next record.
> >>>
> >>> Fixes: fedf201e1296 ("net: tls: Refactor control message handling on
> >>> recv")
> >>> Signed-off-by: Boris Pismenny <borisp@...lanox.com>
> >>> Reviewed-by: Eran Ben Elisha <eranbe@...lanox.com>
> >>> ---
> >>>   net/tls/tls_sw.c | 15 +++++++--------
> >>>   1 file changed, 7 insertions(+), 8 deletions(-)
> >>>
> >>> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index
> >>> f515cd7e984e..85da10182d8d 100644
> >>> --- a/net/tls/tls_sw.c
> >>> +++ b/net/tls/tls_sw.c
> >>> @@ -1481,18 +1481,17 @@ static int decrypt_skb_update(struct sock
> >>> *sk, struct sk_buff *skb,
> >>>
> >>>   			return err;
> >>>   		}
> >>> -
> >>> -		rxm->full_len -= padding_length(ctx, tls_ctx, skb);
> >>> -
> >>> -		rxm->offset += prot->prepend_size;
> >>> -		rxm->full_len -= prot->overhead_size;
> >>> -		tls_advance_record_sn(sk, &tls_ctx->rx, version);
> >>> -		ctx->decrypted = true;
> >>> -		ctx->saved_data_ready(sk);
> >>>   	} else {
> >>>   		*zc = false;
> >>>   	}
> >>>
> >>> +	rxm->full_len -= padding_length(ctx, tls_ctx, skb);
> >>> +	rxm->offset += prot->prepend_size;
> >>> +	rxm->full_len -= prot->overhead_size;
> >>> +	tls_advance_record_sn(sk, &tls_ctx->rx, version);
> >>> +	ctx->decrypted = true;
> >>> +	ctx->saved_data_ready(sk);
> >>> +
> >>>   	return err;
> >>>   }
> >>
> >> This breaks the tls.control_msg test:
> >>
> >>    [ RUN      ] tls.control_msg
> >>    tls.c:764:tls.control_msg:Expected memcmp(buf, test_str, send_len)
> >> (18446744073709551614) == 0 (0)
> >>    tls.c:777:tls.control_msg:Expected memcmp(buf, test_str, send_len)
> >> (18446744073709551614) == 0 (0)
> >>    tls.control_msg: Test failed at step #8
> >>
> >> So either control message handling needs to only call
> >> decrypt_skb_update once, or we need a new flag or something to handle
> >> the device case
> >
> > I prefer to remove variable 'decrypted' in context.
> > This is no longer required as we already have an rx_list in context for
> storing decrypted records.
> > So for any record which we decrypted but did not return to user space
> > (e.g. for the case when user used recv() and it lead to decryption of
> > non-data record), we should it in rx_list.
> >
> 
> IMO this is inappropriate here, because packets decrypted by tls_device are
> ready to be received, and there is no reason to bounce them through the
> rx_list.

My point was about preventing tls_sw_recvmsg() from calling decrypt_skb_update()
with an already decrypted record. The test case failed because an already decrypted record
got dequeued and passed to decrypt_skb_update() from tls_sw_recvmsg().
For packets decrypted by device, a check using skb->decrypted should be enough.

For now, I think your patch is ok.
I can submit a simplification patch for removing 'decrypted' from tls context later.