Messages in this thread | | | Date | Wed, 22 Oct 2014 09:42:46 +0400 | From | Andrey Ryabinin <> | Subject | Re: [PATCH] mm, hugetlb: correct bit shift in hstate_sizelog |
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On 10/21/2014 10:15 PM, Sasha Levin wrote: > hstate_sizelog() would shift left an int rather than long, triggering > undefined behaviour and passing an incorrect value when the requested > page size was more than 4GB, thus breaking >4GB pages.
> > Signed-off-by: Sasha Levin <sasha.levin@oracle.com> > --- > include/linux/hugetlb.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 65e12a2..57e0dfd 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -312,7 +312,8 @@ static inline struct hstate *hstate_sizelog(int page_size_log) > { > if (!page_size_log) > return &default_hstate; > - return size_to_hstate(1 << page_size_log); > + > + return size_to_hstate(1UL << page_size_log);
That still could be undefined on 32-bits. Either use 1ULL or reduce SHM_HUGE_MASK on 32bits.
> } > > static inline struct hstate *hstate_vma(struct vm_area_struct *vma) >
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