4.14-stable review patch. If anyone has any objections, please let me know.
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From: John Fastabend john.fastabend@gmail.com
[ Upstream commit 67db7cd249e71f64346f481b629724376d063e08 ]
Currently, the lower protocols sk_write_space handler is not called if TLS is sending a scatterlist via tls_push_sg. However, normally tls_push_sg calls do_tcp_sendpage, which may be under memory pressure, that in turn may trigger a wait via sk_wait_event. Typically, this happens when the in-flight bytes exceed the sdnbuf size. In the normal case when enough ACKs are received sk_write_space() will be called and the sk_wait_event will be woken up allowing it to send more data and/or return to the user.
But, in the TLS case because the sk_write_space() handler does not wake up the events the above send will wait until the sndtimeo is exceeded. By default this is MAX_SCHEDULE_TIMEOUT so it look like a hang to the user (especially this impatient user). To fix this pass the sk_write_space event to the lower layers sk_write_space event which in the TCP case will wake any pending events.
I observed the above while integrating sockmap and ktls. It initially appeared as test_sockmap (modified to use ktls) occasionally hanging. To reliably reproduce this reduce the sndbuf size and stress the tls layer by sending many 1B sends. This results in every byte needing a header and each byte individually being sent to the crypto layer.
Signed-off-by: John Fastabend john.fastabend@gmail.com Acked-by: Dave Watson davejwatson@fb.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tls/tls_main.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
--- a/net/tls/tls_main.c +++ b/net/tls/tls_main.c @@ -195,9 +195,14 @@ static void tls_write_space(struct sock { struct tls_context *ctx = tls_get_ctx(sk);
- /* We are already sending pages, ignore notification */ - if (ctx->in_tcp_sendpages) + /* If in_tcp_sendpages call lower protocol write space handler + * to ensure we wake up any waiting operations there. For example + * if do_tcp_sendpages where to call sk_wait_event. + */ + if (ctx->in_tcp_sendpages) { + ctx->sk_write_space(sk); return; + }
if (!sk->sk_write_pending && tls_is_pending_closed_record(ctx)) { gfp_t sk_allocation = sk->sk_allocation;