[PATCH] HID: ft260: validate report size in raw_event handler

[Sebastian Josue Alba Vives <sebasjosue84@gmail.com>]

ft260_raw_event() casts the raw data buffer to a
ft260_i2c_input_report struct and accesses its fields without
validating the size parameter. Since __hid_input_report() invokes
the driver's raw_event callback before hid_report_raw_event()
performs its own report-size validation, a device sending a
truncated HID report can cause out-of-bounds heap reads in the
kernel.

In the I2C response path, xfer->length (data[1]) is used as the
length for a memcpy into dev->read_buf. While xfer->length is
checked against dev->read_len, there is no check that size is large
enough to actually contain xfer->length bytes of data starting at
offset 2. A malicious USB device could therefore cause an OOB read
from the kernel heap, with the result accessible from userspace via
the I2C read interface.

FT260 devices use 64-byte HID reports. Add a check at the top of
the handler to reject any report shorter than expected, and log a
warning to aid debugging.

Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Josue Alba Vives <sebasjosue84@gmail.com>
---
 drivers/hid/hid-ft260.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index 333341e80..7ca323992 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -1068,6 +1068,12 @@ static int ft260_raw_event(struct hid_device *hdev, struct hid_report *report,
 	struct ft260_device *dev = hid_get_drvdata(hdev);
 	struct ft260_i2c_input_report *xfer = (void *)data;
 
+	/* FT260 always sends 64-byte reports */
+	if (size < 64) {
+		hid_warn(hdev, "report too short: %d < 64\n", size);
+		return 0;
+	}
+
 	if (xfer->report >= FT260_I2C_REPORT_MIN &&
 	    xfer->report <= FT260_I2C_REPORT_MAX) {
 		ft260_dbg("i2c resp: rep %#02x len %d\n", xfer->report,
-- 
2.43.0