Re: [PATCH] beep: fix division by zero when -f 0 is passed

On Tue, 26 May 2026 11:14:48 +0300
Anton Moryakov via busybox <[email protected]> wrote:

> Static analysis reported potential division by zero at:
>     tickrate_div_freq = CLOCK_TICK_RATE / xatou(optarg);
> 
> If user passes \"-f 0\", xatou() returns 0, causing undefined behavior.
> 
> Fix: validate frequency range (20-50000 Hz) to match CONFIG limits.
> Reject values outside range with clear error message.
> 
> Also removes the old TODO comment about handling -f 0.
> 
> Signed-off-by: Anton Moryakov <[email protected]>
> ---
>  miscutils/beep.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/miscutils/beep.c b/miscutils/beep.c
> index 724a666c8..1d713a004 100644
> --- a/miscutils/beep.c
> +++ b/miscutils/beep.c
> @@ -86,8 +86,13 @@ int beep_main(int argc, char **argv)
>   */
>  		switch (c) {
>  		case 'f':
> -/* TODO: what "-f 0" should do? */
> -			tickrate_div_freq = (unsigned)CLOCK_TICK_RATE / xatou(optarg);
> +/* Frequency 0 is invalid, rejected above */
> +			{	
> +				unsigned freq = xatou(optarg);
> +				if (freq < 20 || freq > 50000)
> +					bb_error_msg_and_die("frequency must be 20-50000 Hz");
Hi,
use xatou_range here:
				xatou_range(optarg, 20, 50000);
> +				tickrate_div_freq = CLOCK_TICK_RATE / freq;
> +			}
>  			continue;
>  		case 'l':
>  			length = xatou(optarg);

Ciao,
Tito