On 16/10/2024 12:22, Mauro Carvalho Chehab wrote:
There is a hidden overflow condition there. As date is signed and u8 is unsigned, doing:
date = (data[0] << 24)
With a value bigger than 07f will make all upper bits of date 0xffffffff. This can be demonstrated with this small code:
<code>
typedef int64_t time64_t; typedef uint8_t u8;
int main(void) { u8 data[] = { 0xde ,0xad , 0xbe, 0xef }; time64_t date;
date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3]; printf("Invalid data = 0x%08lx\n", date);
date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3]; printf("Expected data = 0x%08lx\n", date);
return 0; }
</code>
Fix it by converting the upper bit calculation to unsigned.
Fixes: cea28e7a55e7 ("media: pulse8-cec: reorganize function order") Cc: stable@vger.kernel.org
Not a fix either, just an improvement. The worst that can happen is that in 2038 the wrong date is shown, provided they release new firmware for this device in that year :-)
Regards,
Hans
Signed-off-by: Mauro Carvalho Chehab mchehab+huawei@kernel.org
drivers/media/cec/usb/pulse8/pulse8-cec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/cec/usb/pulse8/pulse8-cec.c b/drivers/media/cec/usb/pulse8/pulse8-cec.c index ba67587bd43e..171366fe3544 100644 --- a/drivers/media/cec/usb/pulse8/pulse8-cec.c +++ b/drivers/media/cec/usb/pulse8/pulse8-cec.c @@ -685,7 +685,7 @@ static int pulse8_setup(struct pulse8 *pulse8, struct serio *serio, err = pulse8_send_and_wait(pulse8, cmd, 1, cmd[0], 4); if (err) return err;
- date = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
- date = ((unsigned)data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3]; dev_info(pulse8->dev, "Firmware build date %ptT\n", &date);
dev_dbg(pulse8->dev, "Persistent config:\n");