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

2009/10/17 FUJITA Tomonori [off-list ref]:

On Tue, 13 Oct 2009 18:10:17 +0900
Akinobu Mita [off-list ref] wrote:

quoted

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>
---
=A0lib/iommu-helper.c | =A0 =A02 +-
=A01 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:

=A0 =A0 =A0 index =3D (index + align_mask) & ~align_mask;

=A0 =A0 =A0 end =3D index + nr;
- =A0 =A0 if (end >=3D size)
+ =A0 =A0 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 =3D find_next_zero_area(map, 64, 0, 64, 0);
        if (offset >=3D 64)
                printf("not found\n");
        else
                printf("found\n");