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

[Pan Xinhui <xinhuix.pan@intel.com>]

hi, Yury

On 2015年06月30日 16:32, Yury Norov wrote:
> 2015-07-01 4:37 GMT+03:00 Pan Xinhui <xinhuix.pan@intel.com>:
>> 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.
>>
>
> Hmm...
> I don't think this is wrong passing echo "1-3,".
> With or without a comma, the final result must be the same.
> More flexible format is useful for hard scripts (for your one).
> It's not too difficult to imagine a script producing a line:
>           "1-24,  ,   ,,, ,  12-64, 92,92,92,,,"
> And I don't think we should reject user with this once the range is valid.
> Even more, to spend a time writing some additional code for it, and make
> user spend his time as well.
>
> I just tried
>            cd /home/yury///./././/work
> and it works perfectly well for me, and it's fine.
>
> The true problem is that a and b variables
> goes zero after comma, and EOL after comma just takes it:
>   514     do {
>   ...
>   517         a = b = 0;                                           //
> <--- comma makes it 0 here
>   ...
>   520         while (buflen) {
>   ...
>   539             /* A '\0' or a ',' signal the end of a cpu# or range */
>   540             if (c == '\0' || c == ',')                     //
> <---here we just break after '\0'
>   541                 break;
>   559         }
>   ...
>   565             while (a <= b) {
>   566                 set_bit(a, maskp);                   // <--- and
> here we set unneeded 0 bit.
>   567                 a++;
>   568             }
>
> So currently, "1-3,\0" is the same as "1-3,0,\0". And this is definitely wrong.
>
yes, you are right.
current codes did not check if there is any digit between ',' or '\0'.
I has sent out patch V2, which rewrite two functions.
could you help have a code review if you have free time? thanks for your nice reply :)

thanks,
xinhui

>>
>>>>
>>>> just like __bitmap_parse, we return -EINVAL if there is no avaiable digit
>>>> in each
>>>> parsing procedures.
>>>>
>>>> Signed-off-by: Pan Xinhui <xinhuix.pan@intel.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