Re: [PATCH] lib/bitmap.c: add some check to correct the parse result

[Pan Xinhui]

hi, Andrew
	thanks for you kind reply :)

On 2015å07æ10æ 06:57, Andrew Morton wrote:
> On Sat, 27 Jun 2015 14:36:18 +0800 Pan Xinhui <xinhuix.pan@xxxxxxxxx> wrote:
> 
>> Sometimes the input from user may cause an unexpected result.
>>
>> for example, echo "1-3," > /proc/irq/<xxx>/smp_affinity_list.
>> The correct result should be 1-3, however we got 0-4.
>>
>> To avoid this issue, we check if there is a ready digit.
>> If no valid digit is set, we just continue to the next parse.
>>
>> Signed-off-by: Pan Xinhui <xinhuix.pan@xxxxxxxxx>
>> ---
>>   lib/bitmap.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/lib/bitmap.c b/lib/bitmap.c
>> index 64c0926..3c489c1 100644
>> --- a/lib/bitmap.c
>> +++ b/lib/bitmap.c
>> @@ -561,6 +561,8 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>>   			return -EINVAL;
>>   		if (b >= nmaskbits)
>>   			return -ERANGE;
>> +		if (unlikely(exp_digit))
>> +			continue;
>>   		while (a <= b) {
>>   			set_bit(a, maskp);
>>   			a++;
> 
> This bug might have been fixed by 2528a8b8f457d7 ("__bitmap_parselist:
> fix bug in empty string handling"), below.  Please check?
> 
> 
Yes, I noticed it after I sent this patch out. Sorry for not syncing the upstream codes.
I am very happy that you reviewed my patch :)

I send out other three patches to make current codes stronger :)
they are
[PATCH 1/3] lib/bitmap.c: correct a code style and do some optimization in __bitmap_parse
[PATCH 2/3] lib/bitmap.c: fix a special string handling bug in  __bitmap_parselist
[PATCH 3/3] lib/bitmap.c: bitmap_parselist can accept string with  whitespaces on head or tail
Of course I have verified/test them :)
They have minor codes change.

thanks
xinhui

> commit 2528a8b8f457d7432552d0e2b6f0f4046bb702f4
> Author:     Chris Metcalf <cmetcalf@xxxxxxxxxx>
> AuthorDate: Thu Jun 25 15:02:08 2015 -0700
> Commit:     Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> CommitDate: Thu Jun 25 17:00:40 2015 -0700
> 
>     __bitmap_parselist: fix bug in empty string handling
>     
>     bitmap_parselist("", &mask, nmaskbits) will erroneously set bit zero in
>     the mask.  The same bug is visible in cpumask_parselist() since it is
>     layered on top of the bitmask code, e.g.  if you boot with "isolcpus=",
>     you will actually end up with cpu zero isolated.
>     
>     The bug was introduced in commit 4b060420a596 ("bitmap, irq: add
>     smp_affinity_list interface to /proc/irq") when bitmap_parselist() was
>     generalized to support userspace as well as kernelspace.
>     
>     Fixes: 4b060420a596 ("bitmap, irq: add smp_affinity_list interface to /proc/irq")
>     Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
>     Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
>     Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>     Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 64c0926..40162f8 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -506,12 +506,12 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>  	unsigned a, b;
>  	int c, old_c, totaldigits;
>  	const char __user __force *ubuf = (const char __user __force *)buf;
> -	int exp_digit, in_range;
> +	int at_start, in_range;
>  
>  	totaldigits = c = 0;
>  	bitmap_zero(maskp, nmaskbits);
>  	do {
> -		exp_digit = 1;
> +		at_start = 1;
>  		in_range = 0;
>  		a = b = 0;
>  
> @@ -540,11 +540,10 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>  				break;
>  
>  			if (c == '-') {
> -				if (exp_digit || in_range)
> +				if (at_start || in_range)
>  					return -EINVAL;
>  				b = 0;
>  				in_range = 1;
> -				exp_digit = 1;
>  				continue;
>  			}
>  
> @@ -554,16 +553,18 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>  			b = b * 10 + (c - '0');
>  			if (!in_range)
>  				a = b;
> -			exp_digit = 0;
> +			at_start = 0;
>  			totaldigits++;
>  		}
>  		if (!(a <= b))
>  			return -EINVAL;
>  		if (b >= nmaskbits)
>  			return -ERANGE;
> -		while (a <= b) {
> -			set_bit(a, maskp);
> -			a++;
> +		if (!at_start) {
> +			while (a <= b) {
> +				set_bit(a, maskp);
> +				a++;
> +			}
>  		}
>  	} while (buflen && c == ',');
>  	return 0;
> 
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