Re: [PATCH bpf-next v1 1/2] bpf,ktls: Fix data corruption when using bpf_msg_pop_data() in ktls
From: Cong Wang <hidden>
Date: 2025-05-29 18:16:13
Also in:
bpf, linux-kselftest, lkml
On Fri, May 23, 2025 at 09:18:58PM +0800, Jiayuan Chen wrote:
quoted hunk ↗ jump to hunk
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 <redacted> Signed-off-by: Jiayuan Chen <redacted> --- net/tls/tls_sw.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index fc88e34b7f33..b23a4655be6a 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c@@ -872,6 +872,21 @@ static int bpf_exec_tx_verdict(struct sk_msg *msg, struct sock *sk, 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. + */ + if (!WARN_ON_ONCE(!ctx->open_rec)) {
I am wondering if we need to WARN here? Because the code below this
handles it gracefully:
931 bool reset_eval = !ctx->open_rec;
932
933 rec = ctx->open_rec;
934 if (rec) {
935 msg = &rec->msg_plaintext;
936 if (!msg->apply_bytes)
937 reset_eval = true;
938 }
939 if (reset_eval) {
940 psock->eval = __SK_NONE;
941 if (psock->sk_redir) {
942 sock_put(psock->sk_redir);
943 psock->sk_redir = NULL;
944 }
945 }
Thanks for fixing it!
Cong