Re: [PATCH net] net/tls: Consume empty data records in tls_sw_read_sock()

[Paolo Abeni <pabeni@redhat.com>]

On 7/7/26 9:58 AM, Sabrina Dubroca wrote:
> 2026-07-06, 15:16:21 -0400, Chuck Lever wrote:
>> On Thu, Jul 2, 2026, at 5:50 PM, Sabrina Dubroca wrote:
>>> 2026-07-02, 15:52:49 -0400, Chuck Lever wrote:
>>>>
>>>>
>>>> On Thu, Jul 2, 2026, at 2:05 PM, Sabrina Dubroca wrote:
>>>>> 2026-06-30, 15:15:51 -0400, Chuck Lever wrote:
>>>>>> A peer may send a zero-length TLS application_data record; TLS 1.3
>>>>>> explicitly permits these as a traffic-analysis countermeasure (RFC
>>>>>> 8446, Section 5.1). After decryption such a record has full_len ==
>>>>>> 0. tls_sw_read_sock() hands it to the read_actor, which has no
>>>>>> payload to consume and returns zero. The loop treats a zero return
>>>>>> as backpressure (used <= 0), requeues the skb at the head of
>>>>>> rx_list, and stops. rx_list is serviced head-first on the next
>>>>>> call, so the empty record is dequeued, fails the same way, and is
>>>>>> requeued again; every later record on the connection is blocked
>>>>>> behind it.
>>>>>>
>>>>>> tls_sw_recvmsg() does not stall on this: a zero-length data record
>>>>>> copies nothing and falls through to consume_skb(). Mirror that in
>>>>>> the read_sock() path by recognizing an empty data record before
>>>>>> the actor runs, consuming it, and continuing.
>>>>>>
>>>>>> Fixes: 662fbcec32f4 ("net/tls: implement ->read_sock()")
>>>>>> Signed-off-by: Chuck Lever <cel@kernel.org>
>>>>>> ---
>>>>>>  net/tls/tls_sw.c | 11 +++++++++++
>>>>>>  1 file changed, 11 insertions(+)
>>>>>
>>>>> Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
>>>>>
>>>>> I think tls_sw_splice_read() suffers from a similar issue (returning 0
>>>>> even though more data may be available). Sashiko agrees, and also
>>>>> found a few more pre-existing issues.
>>>>
>>>> Do you want a v2 series with those issues addressed?
>>>
>>> I'd be ok with this patch going in on its own, and the other issues
>>> being addressed separately. If you have time to look into those,
>>> that'd be great.
>>
>> patchwork shows this patch continues to be marked as "New". Is there
>> something I need to do to help move it forward?
> 
> I don't think there's anything blocking it other than the length of
> the maintainers' backlog.

As noted yday:

https://lore.kernel.org/netdev/c0cd72bd-6298-47a4-82a3-c43811c98063@redhat.com/

current patch processing capacity is limited.

I'm processing this one right now.

/P