[PATCH] tls: rx: restore msg_iter before TLS 1.3 optimistic retry
From: Jérémy Jean <hidden>
Date: 2026-08-04 12:55:54
Also in:
stable
Subsystem:
kernel selftest framework, networking [general], networking [tls], the rest · Maintainers:
Shuah Khan, Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, John Fastabend, Sabrina Dubroca, Linus Torvalds
tls_decrypt_sg() advances msg->msg_iter when it maps user pages for
the optimistic TLS 1.3 zero-copy path. If the decrypted record turns
out not to be unpadded application data, tls_decrypt_sw() retries into
a kernel skb, but leaves the iterator advanced.
The subsequent copy from the skb then writes decrypted bytes again at
a later point in the caller iovecs while recvmsg() reports only the
post-retry length. A TLS peer can trigger this after the receiver
enables TLS_RX_EXPECT_NO_PAD.
Revert the iterator by the number of bytes consumed by the optimistic
mapping before retrying without zero-copy.
Add a selftest which sends a TLS 1.3 control record with
TLS_RX_EXPECT_NO_PAD enabled and verifies that recvmsg() does not
overwrite later iovecs beyond the returned length.
Fixes: ce61327ce989 ("tls: rx: support optimistic decrypt to user buffer with TLS 1.3")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5
Signed-off-by: Jérémy Jean <redacted>
---
net/tls/tls_sw.c | 2 ++
tools/testing/selftests/net/tls.c | 57 +++++++++++++++++++++++++++++++
2 files changed, 59 insertions(+)
diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index d4afc90fd796..fcf95978be38 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c@@ -1442,6 +1442,8 @@ tls_decrypt_sw(struct sock *sk, struct tls_context *tls_ctx, /* If opportunistic TLS 1.3 ZC failed retry without ZC */ if (unlikely(darg->zc && prot->version == TLS_1_3_VERSION && darg->tail != TLS_RECORD_TYPE_DATA)) { + iov_iter_revert(&msg->msg_iter, strp_msg(darg->skb)->full_len - + prot->overhead_size); darg->zc = false; if (!darg->tail) TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXNOPADVIOL);
diff --git a/tools/testing/selftests/net/tls.c b/tools/testing/selftests/net/tls.c
index cbdd3ea28b99..af5e3314c017 100644
--- a/tools/testing/selftests/net/tls.c
+++ b/tools/testing/selftests/net/tls.c@@ -1802,6 +1802,63 @@ TEST_F(tls, recv_efault) } #define TLS_RECORD_TYPE_HANDSHAKE 0x16 + +TEST_F(tls_basic, recvmsg_nopad_retry_iov) +{ + char payload[32]; + char first_iov[sizeof(payload)]; + char later_iov[sizeof(payload) * 2]; + char expected_later_iov[sizeof(later_iov)]; + char cbuf[CMSG_SPACE(sizeof(char))]; + struct tls_crypto_info_keys tls13; + struct iovec iov[] = { + { .iov_base = first_iov, .iov_len = sizeof(first_iov) }, + { .iov_base = later_iov, .iov_len = sizeof(later_iov) }, + }; + struct msghdr msg = { + .msg_iov = iov, + .msg_iovlen = ARRAY_SIZE(iov), + .msg_control = cbuf, + .msg_controllen = sizeof(cbuf), + }; + int one = 1; + int ret; + int i; + + if (self->notls) + SKIP(return, "no TLS support"); + + tls_crypto_info_init(TLS_1_3_VERSION, TLS_CIPHER_AES_GCM_128, + &tls13, 0); + + ret = setsockopt(self->fd, SOL_TLS, TLS_TX, &tls13, tls13.len); + ASSERT_EQ(ret, 0); + + ret = setsockopt(self->cfd, SOL_TLS, TLS_RX, &tls13, tls13.len); + ASSERT_EQ(ret, 0); + + ret = setsockopt(self->cfd, SOL_TLS, TLS_RX_EXPECT_NO_PAD, + &one, sizeof(one)); + ASSERT_EQ(ret, 0); + + for (i = 0; i < sizeof(payload); i++) + payload[i] = 0x40 + i; + memset(first_iov, 0xa5, sizeof(first_iov)); + memset(later_iov, 0x5a, sizeof(later_iov)); + memset(expected_later_iov, 0x5a, sizeof(expected_later_iov)); + + /* A control record forces optimistic TLS 1.3 RX to retry. */ + ret = tls_send_cmsg(self->fd, TLS_RECORD_TYPE_HANDSHAKE, + payload, sizeof(payload), 0); + ASSERT_EQ(ret, sizeof(payload)); + + ret = recvmsg(self->cfd, &msg, 0); + ASSERT_EQ(ret, sizeof(payload)); + EXPECT_EQ(memcmp(first_iov, payload, sizeof(payload)), 0); + EXPECT_EQ(memcmp(later_iov, expected_later_iov, + sizeof(later_iov)), 0); +} + /* key_update, length 1, update_not_requested */ static const char key_update_msg[] = "\x18\x00\x00\x01\x00"; static void tls_send_keyupdate(struct __test_metadata *_metadata, int fd)
--
2.47.3