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

[Sabrina Dubroca <sd@queasysnail.net>]

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.

-- 
Sabrina