[PATCH v2] media: require two-byte Cypress type 04 records

[Pengpeng Hou]

Both Cypress Intel HEX parsers read two address bytes from type 04
records. Generic record framing permits any record length, so a short
record can make the parser consume the checksum or bytes beyond the
firmware record. A longer record also violates the Intel HEX type 04
layout.

Require the type 04 payload length to be exactly two bytes in both
implementations.

Fixes: 79a63c60a6a2 ("[media] media: move dvb-usb-v2/cypress_firmware.c to media/common")
Fixes: 776338e121b9 ("[PATCH] dvb: Add generalized dvb-usb driver")
Assisted-by: Codex:gpt-5
Signed-off-by: Pengpeng Hou <pengpeng@xxxxxxxxxxx>
---
Changes since v1: https://lore.kernel.org/all/20260715084129.36795-1-pengpeng@xxxxxxxxxxx/
- enforce the Intel HEX type 04 exact two-byte payload contract
- apply the same contract to both independent Cypress parsers

The Intel HEX record contract was reviewed statically; malformed firmware
was not injected into either Cypress loader.

 drivers/media/common/cypress_firmware.c      | 2 ++
 drivers/media/usb/dvb-usb/dvb-usb-firmware.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/drivers/media/common/cypress_firmware.c b/drivers/media/common/cypress_firmware.c
index 66274fdf5243..d0f66ed01c4b 100644
--- a/drivers/media/common/cypress_firmware.c
+++ b/drivers/media/common/cypress_firmware.c
@@ -59,6 +59,8 @@ static int cypress_get_hexline(const struct firmware *fw,
 	if (hx->type == 0x04) {
 		/* b[4] and b[5] are the Extended linear address record data
 		 * field */
+		if (hx->len != 2)
+			return -EINVAL;
 		hx->addr |= (b[4] << 24) | (b[5] << 16);
 	}
 
diff --git a/drivers/media/usb/dvb-usb/dvb-usb-firmware.c b/drivers/media/usb/dvb-usb/dvb-usb-firmware.c
index 0fb3fa6100e4..675d9d1d4f47 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-firmware.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-firmware.c
@@ -141,6 +141,8 @@ int dvb_usb_get_hexline(const struct firmware *fw, struct hexline *hx,
 
 	if (hx->type == 0x04) {
 		/* b[4] and b[5] are the Extended linear address record data field */
+		if (hx->len != 2)
+			return -EINVAL;
 		hx->addr |= (b[4] << 24) | (b[5] << 16);
 /*		hx->len -= 2;
 		data_offs += 2; */
-- 
2.50.1 (Apple Git-155)