linux-hardening - Re: [PATCH] clocksource: Replace all non-returning strlcpy with strscpy

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Date:   Tue, 30 May 2023 11:16:30 -0700
From:   John Stultz <jstultz@...gle.com>
To:     Azeem Shaikh <azeemshaikh38@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        linux-hardening@...r.kernel.org, Stephen Boyd <sboyd@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clocksource: Replace all non-returning strlcpy with strscpy

On Tue, May 30, 2023 at 9:35 AM Azeem Shaikh <azeemshaikh38@...il.com> wrote:
>
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
>
> Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
> ---
>  kernel/time/clocksource.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index 91836b727cef..88cbc1181b23 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -1480,7 +1480,7 @@ static int __init boot_override_clocksource(char* str)
>  {
>         mutex_lock(&clocksource_mutex);
>         if (str)
> -               strlcpy(override_name, str, sizeof(override_name));
> +               strscpy(override_name, str, sizeof(override_name));
>         mutex_unlock(&clocksource_mutex);
>         return 1;
>  }

Sounds reasonable to me.

Acked-by: John Stultz <jstultz@...gle.com>

Thanks for submitting this!
-john