linux-kernel - Re: [PATCH] fix %*s%n in sscanf

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

Message-ID: <2375c9f90909250002o59d5d375i8a670494db02287a@mail.gmail.com>
Date:	Fri, 25 Sep 2009 15:02:35 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Andy Spencer <andy753421@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix %*s%n in sscanf

On Fri, Sep 25, 2009 at 2:27 PM, Andy Spencer <andy753421@...il.com> wrote:
> When using %*s, sscanf should honor conversion specifiers immediately following
> the %*s. For example, the following code should find the position of the end of
> the string "hello".
>
>  int end;
>  char buf[] = "hello    world";
>  sscanf(buf, "%*s%n", &end);
>  printf("%d\n", end);
>
> Ideally, sscanf would advance the fmt and str pointers the same as it would
> without the *, but the code for that is rather complicated and is not included
> in the patch.


Yeah, seems reasonable. So, without your patch, sscanf() in kernel
will ignore everything after '*', right?


>
> Please CC me in replies.
>
>
> Signed-off-by: Andy Spencer <andy753421@...il.com>


Fortunately, a quick grep shows no one uses '%*' in sscanf()
in kernel space:

% grep 'sscanf(.*\".*%\*.*\".*)' -nr ./

For completeness,

Acked-by: WANG Cong <xiyou.wangcong@...il.com>

>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 73a14b8..da2daf2 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1766,7 +1766,7 @@ int vsscanf(const char * buf, const char * fmt, va_list args)
>                 * advance both strings to next white space
>                 */
>                if (*fmt == '*') {
> -                       while (!isspace(*fmt) && *fmt)
> +                       while (!isspace(*fmt) && *fmt != '%' && *fmt)
>                                fmt++;
>                        while (!isspace(*str) && *str)
>                                str++;
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/