On Fri, May 23, 2025 at 09:18:58PM +0800, Jiayuan Chen wrote:
> 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 <xiyou.wangc...@gmail.com>
> Signed-off-by: Jiayuan Chen <jiayuan.c...@linux.dev>
> ---
> 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
