On Mon, Nov 28, 2016 at 3:31 AM, Peter Maydell <peter.mayd...@linaro.org> wrote:
> On 8 November 2016 at 00:34, Alistair Francis
> <alistair.fran...@xilinx.com> wrote:
>> The Cadence UART device emulator calculates speed by dividing the
>> baud rate by a 'baud rate generator' & 'baud rate divider' value.
>> The device specification defines these register values to be
>> non-zero and within certain limits. Checks were recently added when
>> writing to these registers but not when restoring from migration.
>>
>> This patch adds checks when restoring from migration to avoid divide by
>> zero errors.
>>
>> Reported-by: Huawei PSIRT <ps...@huawei.com>
>> Signed-off-by: Alistair Francis <alistair.fran...@xilinx.com>
>> ---
>> V2:
>> - Abort the migration if the data is invalid
>>
>> hw/char/cadence_uart.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
>> index def34cd..9568ac6 100644
>> --- a/hw/char/cadence_uart.c
>> +++ b/hw/char/cadence_uart.c
>> @@ -487,6 +487,13 @@ static int cadence_uart_post_load(void *opaque, int
>> version_id)
>> {
>> CadenceUARTState *s = opaque;
>>
>> + /* Ensure these two aren't invalid numbers */
>> + if (s->r[R_BRGR] <= 1 || s->r[R_BRGR] & 0xFFFF ||
>> + s->r[R_BDIV] <= 3 || s->r[R_BDIV] & 0xFF) {
>> + /* Value is invalid, abort */
>> + return 1;
>> + }
>
> The "s->r[R_BRGR] & 0xFFFF" and "s->r[R_BDIV] & 0xFF" checks
> look wrong -- it's ok for the low bits to be set, it's only
> if high bits are set that we want to abort the migration.
> Missing '~'s ? (I'm surprised this bug doesn't cause migration
> to fail every time.)
Yep, you are right. Those are wrong. I'll fix them up.
I didn't have a migration test case to work with. I will set something
up this time to make sure something like that doesn't slip though.
Thanks,
Alistair
>
> thanks
> -- PMM
