linux-kernel - Re: [PATCH v6 2/5] watchdog: s3c2410_wdt: Fix max

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAPLW+4m4S=j8Z0ue9LcxH+8HBsPKTfLuG9nV+6v4NLE=Qp+wnQ@mail.gmail.com>
Date: Mon, 18 Aug 2025 17:27:13 -0500
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Sangwook Shin <sw617.shin@...sung.com>
Cc: krzk@...nel.org, alim.akhtar@...sung.com, wim@...ux-watchdog.org, 
	linux@...ck-us.net, dongil01.park@...sung.com, khwan.seo@...sung.com, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/5] watchdog: s3c2410_wdt: Fix max_timeout being
 calculated larger

On Sun, Aug 17, 2025 at 9:24 PM Sangwook Shin <sw617.shin@...sung.com> wrote:
>
> Fix the issue of max_timeout being calculated larger than actual value.
> The calculation result of freq / (S3C2410_WTCON_PRESCALE_MAX + 1) /
> S3C2410_WTCON_MAXDIV is smaller than the actual value because the remainder
> is discarded during the calculation process. This leads to a larger
> calculated value for max_timeout compared to the actual settable value.
> To resolve this issue, the order of calculations in the computation process
> has been adjusted.
>
> Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>
> Signed-off-by: Sangwook Shin <sw617.shin@...sung.com>
> ---
>  drivers/watchdog/s3c2410_wdt.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index 95f7207e390a..1e8cf0299713 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -27,6 +27,7 @@
>  #include <linux/mfd/syscon.h>
>  #include <linux/regmap.h>
>  #include <linux/delay.h>
> +#include <linux/math64.h>
>
>  #define S3C2410_WTCON          0x00
>  #define S3C2410_WTDAT          0x04
> @@ -410,9 +411,14 @@ static inline unsigned long s3c2410wdt_get_freq(struct s3c2410_wdt *wdt)
>  static inline unsigned int s3c2410wdt_max_timeout(struct s3c2410_wdt *wdt)
>  {
>         const unsigned long freq = s3c2410wdt_get_freq(wdt);
> +       const u64 n_max = (u64)(S3C2410_WTCON_PRESCALE_MAX + 1) *
> +                       S3C2410_WTCON_MAXDIV * S3C2410_WTCNT_MAXCNT;
> +       u64 t_max = div64_ul(n_max, freq);
>
> -       return S3C2410_WTCNT_MAXCNT / (freq / (S3C2410_WTCON_PRESCALE_MAX + 1)
> -                                      / S3C2410_WTCON_MAXDIV);
> +       if (t_max > UINT_MAX)
> +               t_max = UINT_MAX;
> +
> +       return t_max;
>  }
>

Thanks for working on this, Sangwook! It looks much better now.

>  static int s3c2410wdt_disable_wdt_reset(struct s3c2410_wdt *wdt, bool mask)
> --
> 2.25.1
>