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tls: fix handling of zero-length records on the rx_list

PATCH Applied Jakub Kicinski 3 participants 4 messages Aug 20, 2025 – Aug 21, 2025

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Jakub Kicinski

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#0 lore raw

PATCH 1/2 tls: fix handling of zero-length records on the rx_list

Each recvmsg() call must process either
- only contiguous DATA records (any number of them)
- one non-DATA record

If the next record has different type than what has already been processed we break out of the main processing loop. If the record has already been decrypted (which may be the case for TLS 1.3 where we don't know type until decryption) we queue the pending record to the rx_list. Next recvmsg() will pick it up from there.

Queuing the skb to rx_list after zero-copy decrypt is not possible, since in that case we decrypted directly to the user space buffer, and we don't have an skb to queue (darg.skb points to the ciphertext skb for access to metadata like length).

Only data records are allowed zero-copy, and we break the processing loop after each non-data record. So we should never zero-copy and then find out that the record type has changed. The corner case we missed is when the initial record comes from rx_list, and it's zero length.

Reported-by Muhammad Alifa Ramdhan <[email protected]>
Reported-by Billy Jheng Bing-Jhong <[email protected]>
Fixes 84c61fe1a75b ("tls: rx: do not use the standard strparser")
Reviewed-by Sabrina Dubroca <[email protected]>
Signed-off-by Jakub Kicinski <[email protected]>
---
 net/tls/tls_sw.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
net/tls/tls_sw.c +6 -1
index 51c98a007dda..bac65d0d4e3e 100644
@@ -1808,6 +1808,9 @@ int decrypt_skb(struct sock *sk, struct scatterlist *sgout)
 	return tls_decrypt_sg(sk, NULL, sgout, &darg);
 }
 
+/* All records returned from a recvmsg() call must have the same type.
+ * 0 is not a valid content type. Use it as "no type reported, yet".
+ */
 static int tls_record_content_type(struct msghdr *msg, struct tls_msg *tlm,
 				   u8 *control)
 {

@@ -2051,8 +2054,10 @@ int tls_sw_recvmsg(struct sock *sk,
 	if (err < 0)
 		goto end;
 
+	/* process_rx_list() will set @control if it processed any records */
 	copied = err;
-	if (len <= copied || (copied && control != TLS_RECORD_TYPE_DATA) || rx_more)
+	if (len <= copied || rx_more ||
+	    (control && control != TLS_RECORD_TYPE_DATA))
 		goto end;
 
 	target = sock_rcvlowat(sk, flags & MSG_WAITALL, len);
Signature · 1 line
2.50.1
author maintainer
#1 lore raw

PATCH 2/2 selftests: tls: add tests for zero-length records

Test various combinations of zero-length records. Unfortunately, kernel cannot be coerced into producing those, so hardcode the ciphertext messages in the test.

Signed-off-by Jakub Kicinski <[email protected]>
---
 tools/testing/selftests/net/tls.c | 300 +++++++++++++++++++++++++++++-
 1 file changed, 295 insertions(+), 5 deletions(-)
tools/testing/selftests/net/tls.c +295 -5
index 2b8387a83bc7..0f5640d8dc7f 100644
@@ -181,13 +181,12 @@ static int tls_send_cmsg(int fd, unsigned char record_type,
 	return sendmsg(fd, &msg, flags);
 }
 
-static int tls_recv_cmsg(struct __test_metadata *_metadata,
-			 int fd, unsigned char record_type,
-			 void *data, size_t len, int flags)
+static int __tls_recv_cmsg(struct __test_metadata *_metadata,
+			   int fd, unsigned char *ctype,
+			   void *data, size_t len, int flags)
 {
 	char cbuf[CMSG_SPACE(sizeof(char))];
 	struct cmsghdr *cmsg;
-	unsigned char ctype;
 	struct msghdr msg;
 	struct iovec vec;
 	int n;

@@ -206,7 +205,20 @@ static int tls_recv_cmsg(struct __test_metadata *_metadata,
 	EXPECT_NE(cmsg, NULL);
 	EXPECT_EQ(cmsg->cmsg_level, SOL_TLS);
 	EXPECT_EQ(cmsg->cmsg_type, TLS_GET_RECORD_TYPE);
-	ctype = *((unsigned char *)CMSG_DATA(cmsg));
+	if (ctype)
+		*ctype = *((unsigned char *)CMSG_DATA(cmsg));
+
+	return n;
+}
+
+static int tls_recv_cmsg(struct __test_metadata *_metadata,
+			 int fd, unsigned char record_type,
+			 void *data, size_t len, int flags)
+{
+	unsigned char ctype;
+	int n;
+
+	n = __tls_recv_cmsg(_metadata, fd, &ctype, data, len, flags);
 	EXPECT_EQ(ctype, record_type);
 
 	return n;

@@ -2164,6 +2176,284 @@ TEST_F(tls, rekey_poll_delay)
 	}
 }
 
+struct raw_rec {
+	unsigned int plain_len;
+	unsigned char plain_data[100];
+	unsigned int cipher_len;
+	unsigned char cipher_data[128];
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:0, plaintext: 'Hello world' */
+static const struct raw_rec id0_data_l11 = {
+	.plain_len = 11,
+	.plain_data = {
+		0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f,
+		0x72, 0x6c, 0x64,
+	},
+	.cipher_len = 40,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x23, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x26, 0xa2, 0x33,
+		0xde, 0x8d, 0x94, 0xf0, 0x29, 0x6c, 0xb1, 0xaf,
+		0x6a, 0x75, 0xb2, 0x93, 0xad, 0x45, 0xd5, 0xfd,
+		0x03, 0x51, 0x57, 0x8f, 0xf9, 0xcc, 0x3b, 0x42,
+	},
+};
+
+/* TLS 1.2, AES_CCM, ctrl, seqno:0, plaintext: '' */
+static const struct raw_rec id0_ctrl_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x16, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0x38, 0x7b,
+		0xa6, 0x1c, 0xdd, 0xa7, 0x19, 0x33, 0xab, 0xae,
+		0x88, 0xe1, 0xd2, 0x08, 0x4f,
+	},
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:0, plaintext: '' */
+static const struct raw_rec id0_data_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0xc5, 0x37, 0x90,
+		0x70, 0x45, 0x89, 0xfb, 0x5c, 0xc7, 0x89, 0x03,
+		0x68, 0x80, 0xd3, 0xd8, 0xcc,
+	},
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:1, plaintext: 'Hello world' */
+static const struct raw_rec id1_data_l11 = {
+	.plain_len = 11,
+	.plain_data = {
+		0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f,
+		0x72, 0x6c, 0x64,
+	},
+	.cipher_len = 40,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x23, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x01, 0x3a, 0x1a, 0x9c,
+		0xd0, 0xa8, 0x9a, 0xd6, 0x69, 0xd6, 0x1a, 0xe3,
+		0xb5, 0x1f, 0x0d, 0x2c, 0xe2, 0x97, 0x46, 0xff,
+		0x2b, 0xcc, 0x5a, 0xc4, 0xa3, 0xb9, 0xef, 0xba,
+	},
+};
+
+/* TLS 1.2, AES_CCM, ctrl, seqno:1, plaintext: '' */
+static const struct raw_rec id1_ctrl_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x16, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x01, 0x3e, 0xf0, 0xfe,
+		0xee, 0xd9, 0xe2, 0x5d, 0xc7, 0x11, 0x4c, 0xe6,
+		0xb4, 0x7e, 0xef, 0x40, 0x2b,
+	},
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:1, plaintext: '' */
+static const struct raw_rec id1_data_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x01, 0xce, 0xfc, 0x86,
+		0xc8, 0xf0, 0x55, 0xf9, 0x47, 0x3f, 0x74, 0xdc,
+		0xc9, 0xbf, 0xfe, 0x5b, 0xb1,
+	},
+};
+
+/* TLS 1.2, AES_CCM, ctrl, seqno:2, plaintext: 'Hello world' */
+static const struct raw_rec id2_ctrl_l11 = {
+	.plain_len = 11,
+	.plain_data = {
+		0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f,
+		0x72, 0x6c, 0x64,
+	},
+	.cipher_len = 40,
+	.cipher_data = {
+		0x16, 0x03, 0x03, 0x00, 0x23, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x02, 0xe5, 0x3d, 0x19,
+		0x3d, 0xca, 0xb8, 0x16, 0xb6, 0xff, 0x79, 0x87,
+		0x2a, 0x04, 0x11, 0x3d, 0xf8, 0x64, 0x5f, 0x36,
+		0x8b, 0xa8, 0xee, 0x4c, 0x6d, 0x62, 0xa5, 0x00,
+	},
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:2, plaintext: 'Hello world' */
+static const struct raw_rec id2_data_l11 = {
+	.plain_len = 11,
+	.plain_data = {
+		0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f,
+		0x72, 0x6c, 0x64,
+	},
+	.cipher_len = 40,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x23, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x02, 0xe5, 0x3d, 0x19,
+		0x3d, 0xca, 0xb8, 0x16, 0xb6, 0xff, 0x79, 0x87,
+		0x8e, 0xa1, 0xd0, 0xcd, 0x33, 0xb5, 0x86, 0x2b,
+		0x17, 0xf1, 0x52, 0x2a, 0x55, 0x62, 0x65, 0x11,
+	},
+};
+
+/* TLS 1.2, AES_CCM, ctrl, seqno:2, plaintext: '' */
+static const struct raw_rec id2_ctrl_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x16, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x02, 0xdc, 0x5c, 0x0e,
+		0x41, 0xdd, 0xba, 0xd3, 0xcc, 0xcf, 0x6d, 0xd9,
+		0x06, 0xdb, 0x79, 0xe5, 0x5d,
+	},
+};
+
+/* TLS 1.2, AES_CCM, data, seqno:2, plaintext: '' */
+static const struct raw_rec id2_data_l0 = {
+	.plain_len = 0,
+	.plain_data = {
+	},
+	.cipher_len = 29,
+	.cipher_data = {
+		0x17, 0x03, 0x03, 0x00, 0x18, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x02, 0xc3, 0xca, 0x26,
+		0x22, 0xe4, 0x25, 0xfb, 0x5f, 0x6d, 0xbf, 0x83,
+		0x30, 0x48, 0x69, 0x1a, 0x47,
+	},
+};
+
+FIXTURE(zero_len)
+{
+	int fd, cfd;
+	bool notls;
+};
+
+FIXTURE_VARIANT(zero_len)
+{
+	const struct raw_rec *recs[4];
+	ssize_t recv_ret[4];
+};
+
+FIXTURE_VARIANT_ADD(zero_len, data_data_data)
+{
+	.recs = { &id0_data_l11, &id1_data_l11, &id2_data_l11, },
+	.recv_ret = { 33, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, data_0ctrl_data)
+{
+	.recs = { &id0_data_l11, &id1_ctrl_l0, &id2_data_l11, },
+	.recv_ret = { 11, 0, 11, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, 0data_0data_0data)
+{
+	.recs = { &id0_data_l0, &id1_data_l0, &id2_data_l0, },
+	.recv_ret = { -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, 0data_0data_ctrl)
+{
+	.recs = { &id0_data_l0, &id1_data_l0, &id2_ctrl_l11, },
+	.recv_ret = { 0, 11, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, 0data_0data_0ctrl)
+{
+	.recs = { &id0_data_l0, &id1_data_l0, &id2_ctrl_l0, },
+	.recv_ret = { 0, 0, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, 0ctrl_0ctrl_0ctrl)
+{
+	.recs = { &id0_ctrl_l0, &id1_ctrl_l0, &id2_ctrl_l0, },
+	.recv_ret = { 0, 0, 0, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, 0data_0data_data)
+{
+	.recs = { &id0_data_l0, &id1_data_l0, &id2_data_l11, },
+	.recv_ret = { 11, -EAGAIN, },
+};
+
+FIXTURE_VARIANT_ADD(zero_len, data_0data_0data)
+{
+	.recs = { &id0_data_l11, &id1_data_l0, &id2_data_l0, },
+	.recv_ret = { 11, -EAGAIN, },
+};
+
+FIXTURE_SETUP(zero_len)
+{
+	struct tls_crypto_info_keys tls12;
+	int ret;
+
+	tls_crypto_info_init(TLS_1_2_VERSION, TLS_CIPHER_AES_CCM_128,
+			     &tls12, 0);
+
+	ulp_sock_pair(_metadata, &self->fd, &self->cfd, &self->notls);
+	if (self->notls)
+		return;
+
+	/* Don't install keys on fd, we'll send raw records */
+	ret = setsockopt(self->cfd, SOL_TLS, TLS_RX, &tls12, tls12.len);
+	ASSERT_EQ(ret, 0);
+}
+
+FIXTURE_TEARDOWN(zero_len)
+{
+	close(self->fd);
+	close(self->cfd);
+}
+
+TEST_F(zero_len, test)
+{
+	const struct raw_rec *const *rec;
+	unsigned char buf[128];
+	int rec_off;
+	int i;
+
+	for (i = 0; i < 4 && variant->recs[i]; i++)
+		EXPECT_EQ(send(self->fd, variant->recs[i]->cipher_data,
+			       variant->recs[i]->cipher_len, 0),
+			  variant->recs[i]->cipher_len);
+
+	rec = &variant->recs[0];
+	rec_off = 0;
+	for (i = 0; i < 4; i++) {
+		int j, ret;
+
+		ret = variant->recv_ret[i] >= 0 ? variant->recv_ret[i] : -1;
+		EXPECT_EQ(__tls_recv_cmsg(_metadata, self->cfd, NULL,
+					  buf, sizeof(buf), MSG_DONTWAIT), ret);
+		if (ret == -1)
+			EXPECT_EQ(errno, -variant->recv_ret[i]);
+		if (variant->recv_ret[i] == -EAGAIN)
+			break;
+
+		for (j = 0; j < ret; j++) {
+			while (rec_off == (*rec)->plain_len) {
+				rec++;
+				rec_off = 0;
+			}
+			EXPECT_EQ(buf[j], (*rec)->plain_data[rec_off]);
+			rec_off++;
+		}
+	}
+};
+
 FIXTURE(tls_err)
 {
 	int fd, cfd;
Signature · 1 line
2.50.1
maintainer Reviewed-by on v1 2/2
#2 lore raw

Re: [PATCH net 2/2] selftests: tls: add tests for zero-length records

Quoted 8 lines · Jakub Kicinski

Test various combinations of zero-length records. Unfortunately, kernel cannot be coerced into producing those, so hardcode the ciphertext messages in the test.

Signed-off-by Jakub Kicinski <[email protected]>
---
 tools/testing/selftests/net/tls.c | 300 +++++++++++++++++++++++++++++-
 1 file changed, 295 insertions(+), 5 deletions(-)
Reviewed-by Sabrina Dubroca <[email protected]>
Signature · 1 line
Sabrina
CI Applied
#3 lore raw
In reply to Jakub Kicinski
This series was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:

Hello:

This series was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

Quoted 11 lines · On Tue, 19 Aug 2025 19:19:51 -0700 you wrote:

Each recvmsg() call must process either
- only contiguous DATA records (any number of them)
- one non-DATA record

If the next record has different type than what has already been processed we break out of the main processing loop. If the record has already been decrypted (which may be the case for TLS 1.3 where we don't know type until decryption) we queue the pending record to the rx_list. Next recvmsg() will pick it up from there.

[...]

Here is the summary with links:
- [net,1/2] tls: fix handling of zero-length records on the rx_list

    https://git.kernel.org/netdev/net/c/62708b9452f8
  - [net,2/2] selftests: tls: add tests for zero-length records
    https://git.kernel.org/netdev/net/c/a61a3e961baf

You are awesome, thank you!

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