linux-kernel - Re: [PATCH v4 1/4] lib: vsprintf: scanf: Negative number must have field width

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Date:   Wed, 3 Feb 2021 21:48:45 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, linux@...musvillemoes.dk,
        shuah@...nel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH v4 1/4] lib: vsprintf: scanf: Negative number must have
 field width > 1

On Wed, Feb 03, 2021 at 04:50:06PM +0000, Richard Fitzgerald wrote:
> If a signed number field starts with a '-' the field width must be > 1,
> or unlimited, to allow at least one digit after the '-'.
> 
> This patch adds a check for this. If a signed field starts with '-'
> and field_width == 1 the scanf will quit.
> 
> It is ok for a signed number field to have a field width of 1 if it
> starts with a digit. In that case the single digit can be converted.

Acked-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> ---
>  lib/vsprintf.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 3b53c73580c5..28bb26cd1f67 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -3434,8 +3434,12 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
>  		str = skip_spaces(str);
>  
>  		digit = *str;
> -		if (is_sign && digit == '-')
> +		if (is_sign && digit == '-') {
> +			if (field_width == 1)
> +				break;
> +
>  			digit = *(str + 1);
> +		}
>  
>  		if (!digit
>  		    || (base == 16 && !isxdigit(digit))
> -- 
> 2.20.1
> 

-- 
With Best Regards,
Andy Shevchenko