bpf, ktls: Fix data corruption when using bpf_msg_pop_data() in ktls

[ Upstream commit 178f6a5c8cb3b6be1602de0964cd440243f493c9 ]

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.wangcong@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20250609020910.397930-2-jiayuan.chen@linux.dev
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 5f95f837dfc7fd17a39068c89d0c3aaf418436ad..6ac3dcbe87b5cb02a8a5e51485b2229ce71a29c4 100644 (file)
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -868,6 +868,19 @@ 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) {