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

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: 628329d52474 ("Input: add IMS Passenger Control Unit driver")
Signed-off-by: Dan Carpenter <[e-mail]>
Link: https://lore.kernel.org/r/131fd[e-mail]
Cc: [e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/misc/ims-pcu.c

···
 		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;