Re: [PATCH 2/8] bitmap: Introduce bitmap_set, bitmap_clear,

Akinobu Mita
2009-10-17T14:43:56Z

2009/10/17 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>:
> On Tue, 13 Oct 2009 18:10:17 +0900
> Akinobu Mita <akinobu.mita@gmail.com> wrote:
>
>> My user space testing exposed off-by-one error find_next_zero_area
>> in iommu-helper. Some zero area cannot be found by this bug.
>>
>> Subject: [PATCH] Fix off-by-one error in find_next_zero_area
>>
>> Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
>> ---
>>  lib/iommu-helper.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
>> index 75dbda0..afc58bc 100644
>> --- a/lib/iommu-helper.c
>> +++ b/lib/iommu-helper.c
>> @@ -19,7 +19,7 @@ again:
>>       index = (index + align_mask) & ~align_mask;
>>
>>       end = index + nr;
>> -     if (end >= size)
>> +     if (end > size)
>
> I think that this is intentional; the last byte of the limit doesn't
> work.

It looks ok to me. Without above change, find_next_zero_area cannot
find a 64 bits zeroed area in next sample code.

unsigned long offset;

DECLARE_BITMAP(map, 64);

bitmap_clear(map, 0, 64);
offset = find_next_zero_area(map, 64, 0, 64, 0);
if (offset >= 64)
printf("not found\n");
else
printf("found\n");