On Thu, 30 Jan 2025 14:04:46 +0300
Anton Moryakov <[email protected]> wrote:
> Report of the static analyzer:
> DIVISION_BY_ZERO.EX Variable xatou(...),
> whose possible value set allows a zero value at xatonum_template.c:118 by
> calling function 'xatou' at beep.c:90,
> is used as a denominator at beep.c:90.
>
> Corrections explained:
> Fixed a potential division by zero issue in beep.c.
> The function xatou(optarg) could return0, leading to an undefined behavior
> when used as a denominator.
> Changes:
> - Added a check to ensure the frequency value is nonzero before division. -
> If an invalid frequency (0) is provided, the program exits with an error
> message.
> This fix prevents crashes and ensures safer execution.
>
> Triggers found by static analyzer Svace.
>
> Signed-off-by: Anton Moryakov <ant.v.moryakov at gmail.com>
>
> ---
> miscutils/beep.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/miscutils/beep.c b/miscutils/beep.c
> index 724a666c8..1667757ea 100644
> --- a/miscutils/beep.c
> +++ b/miscutils/beep.c
> @@ -87,6 +87,9 @@ int beep_main(int argc, char **argv)
> switch (c) {
> case 'f':
> /* TODO: what "-f 0" should do? */
> + unsigned freq = xatou(optarg);
> + if (freq == 0)
> + bb_error_msg_and_die("frequency cannot be zero");
> tickrate_div_freq = (unsigned)CLOCK_TICK_RATE /
> xatou(optarg);
> continue;
> case 'l':
Hi,
wouldn't it be enough to use xatou_range:
diff -uNp miscutils/beep.c.orig miscutils/beep.c
--- miscutils/beep.c.orig 2023-07-21 22:23:35.083200110 +0200
+++ miscutils/beep.c 2025-01-30 13:53:32.746176275 +0100
@@ -86,8 +86,7 @@ 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);
+ tickrate_div_freq = (unsigned)CLOCK_TICK_RATE /
xatou_range(optarg, 1, 20000);
continue;
case 'l':
length = xatou(optarg);
Ciao,
Tito
P.S.: even tough man beep says:
-f Beep with a tone frequency of FREQ Hz, where 0 < FREQ < 20000
it also accepts 0 (plays default 440 hz) and 20000:
beep -f 20000 --debug --verbose
beep: Verbose: evdev driver_detect 0x55f1d6a00700 (nil)
beep: Verbose: b-lib: opened /dev/input/by-path/platform-pcspkr-event-spkr as 3
beep: Verbose: beep: using driver 0x55f1d6a00700 (name=evdev, fd=3,
dev=/dev/input/by-path/platform-pcspkr-event-spkr)
beep: Verbose: 1 times 200 ms beeps (100 ms delay between, 0 ms delay after) @
20000 Hz
beep: Verbose: evdev driver_begin_tone 0x55f1d6a00700 20000
beep: Verbose: evdev driver_end_tone 0x55f1d6a00700
beep: Verbose: evdev driver_end_tone 0x55f1d6a00700
beep: Verbose: evdev driver_fini 0x55f1d6a00700
root@devuan:/home/tito# beep -f 20001 --debug --verbose
beep -f 0 --debug --verbose
beep: Verbose: evdev driver_detect 0x55ff9aab2700 (nil)
beep: Verbose: b-lib: opened /dev/input/by-path/platform-pcspkr-event-spkr as 3
beep: Verbose: beep: using driver 0x55ff9aab2700 (name=evdev, fd=3,
dev=/dev/input/by-path/platform-pcspkr-event-spkr)
beep: Verbose: 1 times 200 ms beeps (100 ms delay between, 0 ms delay after) @
440 Hz
beep: Verbose: evdev driver_begin_tone 0x55ff9aab2700 440
beep: Verbose: evdev driver_end_tone 0x55ff9aab2700
beep: Verbose: evdev driver_end_tone 0x55ff9aab2700
beep: Verbose: evdev driver_fini 0x55ff9aab2700
but not 20001.
--- miscutils/beep.c.orig 2023-07-21 22:23:35.083200110 +0200
+++ miscutils/beep.c 2025-01-30 13:53:32.746176275 +0100
@@ -86,8 +86,7 @@ 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);
+ tickrate_div_freq = (unsigned)CLOCK_TICK_RATE / xatou_range(optarg, 1, 20000);
continue;
case 'l':
length = xatou(optarg);
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