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@xxxxxxxxxxxxxxx
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@xxxxxxxxxx>
> ---
> 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");
