[PATCH 2/4] ethdev: check module EEPROM length before decoding

[Roman Khromenok <roma55592@yandex.ru>]

The SFF decoders assume the buffer is large enough for the module
type: SFF-8079 and SFF-8472 do not receive the length at all,
and SFF-8636 only uses it to detect the optional page 03h.
If a driver reports a length shorter than the type requires,
the decoders read past the end of the buffer.

Move the type dispatch into a common internal function which checks
the minimal length for each type before decoding:
- SFF-8079 and SFF-8436/8636 require at least 256 bytes,
- SFF-8472 requires 256 bytes for the base information,
  and the diagnostics (page A2h) are decoded only if 512 bytes
  are available.

This is a preparation for exposing the decoders to applications,
which may pass buffers of arbitrary length.

Signed-off-by: Roman Khromenok <roma55592@yandex.ru>
---
 lib/ethdev/sff_telemetry.c | 37 +++++++++++++++++++++++++++++--------
 lib/ethdev/sff_telemetry.h |  8 ++++++++
 2 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/lib/ethdev/sff_telemetry.c b/lib/ethdev/sff_telemetry.c
index 8c8e95affe..72d55322b6 100644
--- a/lib/ethdev/sff_telemetry.c
+++ b/lib/ethdev/sff_telemetry.c
@@ -99,25 +99,46 @@ sff_port_module_eeprom_parse(uint16_t port_id, struct rte_tel_data *d)
 		return;
 	}
 
-	switch (minfo.type) {
+	ret = sff_decode_module_eeprom(minfo.type, einfo.data, einfo.length, &out);
+	if (ret == -ENOTSUP)
+		RTE_ETHDEV_LOG_LINE(NOTICE, "Unsupported module type: %u", minfo.type);
+	else if (ret != 0)
+		RTE_ETHDEV_LOG_LINE(ERR, "Port %u module EEPROM is too short: %u bytes",
+			port_id, einfo.length);
+
+	free(einfo.data);
+}
+
+int
+sff_decode_module_eeprom(uint32_t type, const uint8_t *data, uint32_t length,
+			 struct sff_output *d)
+{
+	switch (type) {
 	/* parsing module EEPROM data base on different module type */
 	case RTE_ETH_MODULE_SFF_8079:
-		sff_8079_show_all(einfo.data, &out);
+		if (length < RTE_ETH_MODULE_SFF_8079_LEN)
+			return -EINVAL;
+		sff_8079_show_all(data, d);
 		break;
 	case RTE_ETH_MODULE_SFF_8472:
-		sff_8079_show_all(einfo.data, &out);
-		sff_8472_show_all(einfo.data, &out);
+		if (length < RTE_ETH_MODULE_SFF_8079_LEN)
+			return -EINVAL;
+		sff_8079_show_all(data, d);
+		/* diagnostics are in the second page (A2h) */
+		if (length >= RTE_ETH_MODULE_SFF_8472_LEN)
+			sff_8472_show_all(data, d);
 		break;
 	case RTE_ETH_MODULE_SFF_8436:
 	case RTE_ETH_MODULE_SFF_8636:
-		sff_8636_show_all(einfo.data, einfo.length, &out);
+		if (length < RTE_ETH_MODULE_SFF_8636_LEN)
+			return -EINVAL;
+		sff_8636_show_all(data, length, d);
 		break;
 	default:
-		RTE_ETHDEV_LOG_LINE(NOTICE, "Unsupported module type: %u", minfo.type);
-		break;
+		return -ENOTSUP;
 	}
 
-	free(einfo.data);
+	return 0;
 }
 
 void
diff --git a/lib/ethdev/sff_telemetry.h b/lib/ethdev/sff_telemetry.h
index 2a6d79a9c1..1d2c8fd444 100644
--- a/lib/ethdev/sff_telemetry.h
+++ b/lib/ethdev/sff_telemetry.h
@@ -25,6 +25,14 @@ void sff_8472_show_all(const uint8_t *data, struct sff_output *d);
 /* SFF-8636 Optics diagnostics */
 void sff_8636_show_all(const uint8_t *data, uint32_t eeprom_len, struct sff_output *d);
 
+/*
+ * Decode module EEPROM of the given type (RTE_ETH_MODULE_SFF_*).
+ * Returns 0 on success, -EINVAL if the data is too short for the type,
+ * -ENOTSUP if the type is unknown.
+ */
+int sff_decode_module_eeprom(uint32_t type, const uint8_t *data, uint32_t length,
+			     struct sff_output *d);
+
 int eth_dev_handle_port_module_eeprom(const char *cmd __rte_unused,
 				      const char *params,
 				      struct rte_tel_data *d);
-- 
2.47.3