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

On Sat, 17 Oct 2009 23:43:56 +0900
Akinobu Mita [off-list ref] wrote:

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

quoted

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>
---
 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.

I meant that we don't want to find such area for IOMMUs (IIRC, it code
came from POWER IOMMU).

        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");
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