linux-kernel - Re: [PATCH] lib/bitmap.c: return -EINVAL for grouping errors in __bitmap

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Message-ID: <55934441.9010304@intel.com>
Date:	Wed, 01 Jul 2015 09:37:05 +0800
From:	Pan Xinhui <xinhuix.pan@...el.com>
To:	Yury Norov <yury.norov@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>, tj@...nel.org,
	peterz@...radead.org, sudeep.holla@....com, mina86@...a86.com,
	"mnipxh@....com" <mnipxh@....com>,
	Alexey Klimov <klimov.linux@...il.com>
Subject: Re: [PATCH] lib/bitmap.c: return -EINVAL for grouping errors in __bitmap_parselist

hi, Yury
	thanks for your nice reply.

On 2015年06月29日 21:39, Yury Norov wrote:
>> Sometimes the input from user may cause an unexpected result.
>
> Could you please provide specific example?
>
I wrote some scripts to do some tests about irqs.
echo "1-3," > /proc/irq/<xxx>/smp_affinity_list
this command ends with ',' by mistake.
actually __bitmap_parselist() will report "0-3" for the final result which is wrong.

>>
>> just like __bitmap_parse, we return -EINVAL if there is no avaiable digit in each
>> parsing procedures.
>>
>> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
>
> Hello, Pan.
>
> (Adding Alexey Klimov, Rasmus Villemoes)
>
>> ---
>>    lib/bitmap.c | 7 +++++--
>>    1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/bitmap.c b/lib/bitmap.c
>> index 64c0926..995fca2 100644
>> --- a/lib/bitmap.c
>> +++ b/lib/bitmap.c
>> @@ -504,7 +504,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>>            int nmaskbits)
>>    {
>>        unsigned a, b;
>> -    int c, old_c, totaldigits;
>> +    int c, old_c, totaldigits, ndigits;
>>        const char __user __force *ubuf = (const char __user __force *)buf;
>>        int exp_digit, in_range;
>>
>> @@ -514,6 +514,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>>            exp_digit = 1;
>>            in_range = 0;
>>            a = b = 0;
>> +        ndigits = 0;
>>
>>            /* Get the next cpu# or a range of cpu#'s */
>>            while (buflen) {
>> @@ -555,8 +556,10 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>>                if (!in_range)
>>                    a = b;
>>                exp_digit = 0;
>> -            totaldigits++;
>> +            ndigits++; totaldigits++;
>
> I'm not happy with joining two statements to a single line.
> Maybe sometimes it's OK for loop iterators like
>
>      while (a[i][j]) {
>          i++; j++;
>      }
>
> But here it looks nasty. Anyway, it's minor.
>

thanks for pointing out my mistake about the code style :)

>>            }
>> +        if (ndigits == 0)
>> +            return -EINVAL;
>
> You can avoid in-loop incrementation of ndigits if you'll
> save current totaldigits to ndigits before loop, and check
> ndigits against totaldigits after the loop:
>
>      ndigits = totaldigits;
>      while (...) {
>           ...
>          totaldigits++;
>      }
>
>      if (ndigits == totaldigits)
>          return -EINVAL;
>
> Maybe it's a good point to rework initial __bitmap_parse() similar way...
>

your advice is a good idea, thanks.
I am also thinking if we can rewrite them into one function for common codes.

thanks for your reply again :)

thanks
xinhui

>>            if (!(a <= b))
>>                return -EINVAL;
>>            if (b >= nmaskbits)
>> --
>> 1.9.1
--
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