Re: [PATCH 9/9] tools/sched_ext: scx_userland: Reject batch size 0

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] tools/sched_ext: NULL optarg passed to fprintf() in
  pre_bootstrap()
--

commit 0b3057c6e52c8c9370246141c70182a7501b6c0e
Author: Tao Cui <cuitao@kylinos.cn>

tools/sched_ext: scx_userland: Reject batch size 0

This commit rejects a zero batch size in pre_bootstrap() to prevent a
livelock when -b 0 is passed on the command line.

> diff --git a/tools/sched_ext/scx_userland.c b/tools/sched_ext/scx_userland.c
> index b16b6db5f3650..cbd511685449f 100644
> --- a/tools/sched_ext/scx_userland.c
> +++ b/tools/sched_ext/scx_userland.c
> @@ -364,6 +364,11 @@ static void pre_bootstrap(int argc, char **argv)
>  		}
>  	}
>  
> +	if (!batch_size) {
> +		fprintf(stderr, "Invalid batch size %s\n", optarg);
> +		exit(1);
> +	}

[Severity: Low]
Does this pass a NULL optarg to fprintf()?  Because this check runs after
the while ((opt = getopt(...)) != -1) loop finishes, the final getopt()
call has already reset optarg to NULL, which prints "(null)" on glibc and
causes a NULL pointer dereference on libcs such as musl.  Checking
!batch_size inside case 'b' while optarg still points to the argument (or
printing batch_size with %u) would avoid this.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110125001.4167503-1-cui.tao@linux.dev?part=9