Input: ims-pcu - check record size in ims_pcu_flash_firmware()

commit a95ef01 upstream.

The "len" variable comes from the firmware and we generally do
trust firmware, but it's always better to double check.  If the "len"
is too large it could result in memory corruption when we do
"memcpy(fragment->data, rec->data, len);"

Fixes: 628329d ("Input: add IMS Passenger Control Unit driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/131fd1ae92c828ee9f4fa2de03d8c210ae1f3524.1748463049.git.dan.carpenter@linaro.org
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Dan Carpenter

drivers/input/misc/ims-pcu.c

@@ -844,6 +844,12 @@ static int ims_pcu_flash_firmware(struct ims_pcu *pcu,
 		addr = be32_to_cpu(rec->addr) / 2;
 		len = be16_to_cpu(rec->len);
 
+		if (len > sizeof(pcu->cmd_buf) - 1 - sizeof(*fragment)) {
+			dev_err(pcu->dev,
+				"Invalid record length in firmware: %d\n", len);
+			return -EINVAL;
+		}
+
 		fragment = (void *)&pcu->cmd_buf[1];
 		put_unaligned_le32(addr, &fragment->addr);
 		fragment->len = len;