netdev - [PATCH net 5/7] tls: don't rely on tx

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Message-ID: <8396631478f70454b44afb98352237d33f48d34d.1760432043.git.sd@queasysnail.net>
Date: Tue, 14 Oct 2025 11:17:00 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: netdev@...r.kernel.org
Cc: Sabrina Dubroca <sd@...asysnail.net>,
	kuba@...nel.org,
	jannh@...gle.com,
	john.fastabend@...il.com
Subject: [PATCH net 5/7] tls: don't rely on tx_work during send()

With async crypto, we rely on tx_work to actually transmit records
once encryption completes. But while send() is running, both the
tx_lock and socket lock are held, so tx_work_handler cannot process
the queue of encrypted records, and simply reschedules itself. During
a large send(), this could last a long time, and use a lot of memory.

Transmit any pending encrypted records before restarting the main
loop of tls_sw_sendmsg_locked.

Fixes: a42055e8d2c3 ("net/tls: Add support for async encryption of records for performance")
Reported-by: Jann Horn <jannh@...gle.com>
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
Paolo suggests that we could also add memory accounting to
sk_msg_alloc, and reclaim that memory just before pushing the data to
tcp_sendmsg_locked.

 net/tls/tls_sw.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index e3d852091e7a..d17135369980 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1152,6 +1152,13 @@ static int tls_sw_sendmsg_locked(struct sock *sk, struct msghdr *msg,
 				} else if (ret != -EAGAIN)
 					goto send_end;
 			}
+
+			/* Transmit if any encryptions have completed */
+			if (test_and_clear_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask)) {
+				cancel_delayed_work(&ctx->tx_work.work);
+				tls_tx_records(sk, msg->msg_flags);
+			}
+
 			continue;
 rollback_iter:
 			copied -= try_to_copy;
@@ -1207,6 +1214,12 @@ static int tls_sw_sendmsg_locked(struct sock *sk, struct msghdr *msg,
 					goto send_end;
 				}
 			}
+
+			/* Transmit if any encryptions have completed */
+			if (test_and_clear_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask)) {
+				cancel_delayed_work(&ctx->tx_work.work);
+				tls_tx_records(sk, msg->msg_flags);
+			}
 		}
 
 		continue;
-- 
2.51.0