[PATCH] HID: hid-goodix-spi: validate report size to prevent stack buffer overflow

["Tianchu Chen" <tianchu.chen@linux.dev>]

From: Tianchu Chen <flynnnchen@tencent.com>

goodix_hid_set_raw_report() builds a protocol frame in a 128-byte stack
buffer (tmp_buf), writing an 11-12 byte header followed by the
caller-supplied report data.  The HID core caps report size at
HID_MAX_BUFFER_SIZE (16384) by default, while the driver does not set
hid_ll_driver.max_buffer_size and performs no bounds checking before
copying the payload:

    memcpy(tmp_buf + tx_len, buf, len);

A hidraw SET_REPORT ioctl with a report larger than ~116 bytes
overflows the stack buffer.

Add a size check after constructing the header, rejecting reports that
would exceed the buffer capacity.

Discovered by Atuin - Automated Vulnerability Discovery Engine.

Fixes: 75e16c8ce283 ("HID: hid-goodix: Add Goodix HID-over-SPI driver")
Cc: stable@vger.kernel.org
Signed-off-by: Tianchu Chen <flynnnchen@tencent.com>
---
 drivers/hid/hid-goodix-spi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-goodix-spi.c b/drivers/hid/hid-goodix-spi.c
index 80c0288a3..288cb827e 100644
--- a/drivers/hid/hid-goodix-spi.c
+++ b/drivers/hid/hid-goodix-spi.c
@@ -520,6 +520,9 @@ static int goodix_hid_set_raw_report(struct hid_device *hid,
 	memcpy(tmp_buf + tx_len, args, args_len);
 	tx_len += args_len;
 
+	if (tx_len + len > sizeof(tmp_buf))
+		return -EINVAL;
+
 	memcpy(tmp_buf + tx_len, buf, len);
 	tx_len += len;
 
-- 
2.51.0