From 178f6a5c8cb3b6be1602de0964cd440243f493c9 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Mon, 9 Jun 2025 10:08:52 +0800 Subject: [PATCH] bpf, ktls: Fix data corruption when using bpf_msg_pop_data() in ktls When sending plaintext data, we initially calculated the corresponding ciphertext length. However, if we later reduced the plaintext data length via socket policy, we failed to recalculate the ciphertext length. This results in transmitting buffers containing uninitialized data during ciphertext transmission. This causes uninitialized bytes to be appended after a complete "Application Data" packet, leading to errors on the receiving end when parsing TLS record. Fixes: d3b18ad31f93 ("tls: add bpf support to sk_msg handling") Reported-by: Cong Wang Signed-off-by: Jiayuan Chen Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Acked-by: Jakub Kicinski Link: https://lore.kernel.org/bpf/20250609020910.397930-2-jiayuan.chen@linux.dev --- 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 fc88e34b7f33f..549d1ea01a72a 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -872,6 +872,19 @@ more_data: delta = msg->sg.size; psock->eval = sk_psock_msg_verdict(sk, psock, msg); delta -= msg->sg.size; + + if ((s32)delta > 0) { + /* It indicates that we executed bpf_msg_pop_data(), + * causing the plaintext data size to decrease. + * Therefore the encrypted data size also needs to + * correspondingly decrease. We only need to subtract + * delta to calculate the new ciphertext length since + * ktls does not support block encryption. + */ + struct sk_msg *enc = &ctx->open_rec->msg_encrypted; + + sk_msg_trim(sk, enc, enc->sg.size - delta); + } } if (msg->cork_bytes && msg->cork_bytes > msg->sg.size && !enospc && !full_record) { -- 2.47.3