Re: [PATCH] ubi: replace simple_strtoul() with kstrtoul()

Zhang Zhen
2014-05-20T01:19:39Z

On 2014/5/19 17:14, Geert Uytterhoeven wrote:
> Please don't add mindless casts!
>
> On Mon, May 19, 2014 at 10:38 AM, Zhang Zhen <zhenzhang.zhang@huawei.com> wrote:
>> --- a/drivers/mtd/ubi/build.c
>> +++ b/drivers/mtd/ubi/build.c
>> @@ -1190,10 +1190,13 @@ static struct mtd_info * __init open_mtd_by_chdev(const char *mtd_dev)
>> static struct mtd_info * __init open_mtd_device(const char *mtd_dev)
>> {
>> struct mtd_info *mtd;
>> - int mtd_num;
>> + int mtd_num, ret;
>> char *endp;
>>
>> - mtd_num = simple_strtoul(mtd_dev, &endp, 0);
>> + endp = (char *)mtd_dev;
>> + ret = kstrtoul(endp, 0, (unsigned long *)&mtd_num);
>
> On 64-bit, long is 64-bit, hence this will write beyond mtd_num and will corrupt
> the stack.

Yeah, you are right. This really may write beyond dev.

The kstrtoul(const char *s, unsigned int base, unsigned long *res) only accept unsigned long
pointer as the third parameter.
And the original function simple_strtoul() returns unsigned long type value.
It is also cast. So this may not corrupt the stack.

Or do you have any better suggestion about this?
Thanks.
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
>
>