Re: [PATCH 1/2] fuzz: use ITIMER_REAL for timeouts

[Darren Kenny]

On Wednesday, 2021-08-04 at 09:56:20 -04, Alexander Bulekov wrote:
> Using ITIMER_VIRTUAL is a bad idea, if the fuzzer hits a blocking
> syscall - e.g. ppoll with a NULL timespec. This causes timeout issues
> while fuzzing some block-device code. Fix that by using wall-clock time.
> This might cause inputs to timeout sometimes due to scheduling
> effects/ambient load, but it is better than bringing the entire fuzzing
> process to a halt.
>
> Based-on: <20210713150037.9297-1-alxndr@bu.edu>
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>

> ---
>  tests/qtest/fuzz/generic_fuzz.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
> index 3e8ce29227..de427a3727 100644
> --- a/tests/qtest/fuzz/generic_fuzz.c
> +++ b/tests/qtest/fuzz/generic_fuzz.c
> @@ -695,7 +695,7 @@ static void generic_fuzz(QTestState *s, const unsigned 
> char *Data, size_t Size)
>          while (cmd && Size) {
>              /* Reset the timeout, each time we run a new command */
>              if (timeout) {
> -                setitimer(ITIMER_VIRTUAL, &timer, NULL);
> +                setitimer(ITIMER_REAL, &timer, NULL);
>              }
>  
>              /* Get the length until the next command or end of input */
> -- 
> 2.30.2