[PATCH 10/11] Input: ims-pcu - add response length checks

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

The driver processes response data from device buffers without verifying
that the device actually sent enough data. This can lead to
out-of-bounds reads or processing stale data.

Add checks for the expected response length before accessing the
buffers.

Fixes: 628329d52474 ("Input: add IMS Passenger Control Unit driver")
Cc: stable@vger.kernel.org
Reported-by: Sashiko bot <sashiko-bot@kernel.org>
Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/misc/ims-pcu.c | 53 +++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

diff --git a/drivers/input/misc/ims-pcu.c b/drivers/input/misc/ims-pcu.c
index 3b119bc81c85..422b1be62303 100644
--- a/drivers/input/misc/ims-pcu.c
+++ b/drivers/input/misc/ims-pcu.c
@@ -406,7 +406,16 @@ static void ims_pcu_destroy_gamepad(struct ims_pcu *pcu)
 
 static void ims_pcu_report_events(struct ims_pcu *pcu)
 {
-	u32 data = get_unaligned_be32(&pcu->read_buf[3]);
+	u32 data;
+
+	/* 6-axis setting (1 byte) + button data + checksum */
+	if (pcu->read_pos < IMS_PCU_DATA_OFFSET + 1 + sizeof(data) + 1) {
+		dev_warn(pcu->dev, "Short buttons report: %d bytes\n",
+			 pcu->read_pos);
+		return;
+	}
+
+	data = get_unaligned_be32(&pcu->read_buf[IMS_PCU_DATA_OFFSET + 1]);
 
 	ims_pcu_buttons_report(pcu, data & ~IMS_PCU_GAMEPAD_MASK);
 	if (pcu->gamepad)
@@ -718,6 +727,12 @@ static int ims_pcu_get_info(struct ims_pcu *pcu)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + IMS_PCU_SET_INFO_SIZE + 1) {
+		dev_err(pcu->dev, "Short GET_INFO response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	memcpy(pcu->part_number,
 	       &pcu->cmd_buf[IMS_PCU_INFO_PART_OFFSET],
 	       sizeof(pcu->part_number));
@@ -1283,6 +1298,12 @@ static int ims_pcu_read_ofn_config(struct ims_pcu *pcu, u8 addr, u8 *data)
 	if (error)
 		return error;
 
+	if (pcu->cmd_buf_len < OFN_REG_RESULT_OFFSET + 2 + 1) {
+		dev_err(pcu->dev, "Short OFN_GET_CONFIG response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	result = (s16)get_unaligned_le16(pcu->cmd_buf + OFN_REG_RESULT_OFFSET);
 	if (result < 0)
 		return -EIO;
@@ -1843,6 +1864,12 @@ static int ims_pcu_get_device_info(struct ims_pcu *pcu)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + 6 + 1) {
+		dev_err(pcu->dev, "Short GET_FW_VERSION response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	snprintf(pcu->fw_version, sizeof(pcu->fw_version),
 		 "%02d%02d%02d%02d.%c%c",
 		 pcu->cmd_buf[2], pcu->cmd_buf[3], pcu->cmd_buf[4], pcu->cmd_buf[5],
@@ -1855,6 +1882,12 @@ static int ims_pcu_get_device_info(struct ims_pcu *pcu)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + 6 + 1) {
+		dev_err(pcu->dev, "Short GET_BL_VERSION response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	snprintf(pcu->bl_version, sizeof(pcu->bl_version),
 		 "%02d%02d%02d%02d.%c%c",
 		 pcu->cmd_buf[2], pcu->cmd_buf[3], pcu->cmd_buf[4], pcu->cmd_buf[5],
@@ -1867,6 +1900,12 @@ static int ims_pcu_get_device_info(struct ims_pcu *pcu)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + 1 + 1) {
+		dev_err(pcu->dev, "Short RESET_REASON response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	snprintf(pcu->reset_reason, sizeof(pcu->reset_reason),
 		 "%02x", pcu->cmd_buf[IMS_PCU_DATA_OFFSET]);
 
@@ -1893,6 +1932,12 @@ static int ims_pcu_identify_type(struct ims_pcu *pcu, u8 *device_id)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + 1 + 1) {
+		dev_err(pcu->dev, "Short GET_DEVICE_ID response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	*device_id = pcu->cmd_buf[IMS_PCU_DATA_OFFSET];
 	dev_dbg(pcu->dev, "Detected device ID: %d\n", *device_id);
 
@@ -1984,6 +2029,12 @@ static int ims_pcu_init_bootloader_mode(struct ims_pcu *pcu)
 		return error;
 	}
 
+	if (pcu->cmd_buf_len < IMS_PCU_DATA_OFFSET + 15 + 4 + 1) {
+		dev_err(pcu->dev, "Short QUERY_DEVICE response: %d bytes\n",
+			pcu->cmd_buf_len);
+		return -EIO;
+	}
+
 	pcu->fw_start_addr =
 		get_unaligned_le32(&pcu->cmd_buf[IMS_PCU_DATA_OFFSET + 11]);
 	pcu->fw_end_addr =
-- 
2.54.0.746.g67dd491aae-goog