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

["Chuck Lever" <cel@kernel.org>]

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?


-- 
Chuck Lever