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SubjectRe: [PATCH] mm/memblock.c: Correctly check whether to trim a block
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On Wed, 2012-03-28 at 19:25 -0700, Laura Abbott wrote:
> Currently in __memblock_remove, the check to trim the top of
> a block off only checks if the requested base is less than the
> memblock end. If the end of the requested region is equal to
> the start of a memblock, this will incorrectly try to remove
> the block, possibly causing an integer underflow:
>
> ---------------------------------------
> | | |
> | | |
> base end = rgn->base rend
>
> An additional check is needed to see if the end of the requested
> region is greater than the memblock region:

__memblock_remove() open coded logic is gone now, re-implemented
in term of memblock_isolate_range()... though I suppose your
patch might have value in -stable...

Cheers,
Ben.


> ----------------------
> | |
> | |
> rgn->base base rend end
> | |
> | |
> --------------------
>
> Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
> ---
> mm/memblock.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 5338237..e174ee0 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -459,7 +459,7 @@ static long __init_memblock __memblock_remove(struct memblock_type *type,
> }
>
> /* And check if we need to trim the top of a block */
> - if (base < rend)
> + if (base < rend && end > rend)
> rgn->size -= rend - base;
>
> }




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