On Wed, 22 Oct 2014 14:50:22 -0400 Sasha Levin <sasha.levin@xxxxxxxxxx> wrote:
> On 10/22/2014 02:44 PM, Andrew Morton wrote:
> > On Wed, 22 Oct 2014 09:42:46 +0400 Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> wrote:
> >
> >> > 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@xxxxxxxxxx>
> >>> > > ---
> >>> > > 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.
> >> >
> > But
> >
> > struct hstate *size_to_hstate(unsigned long size)
>
> True, but "(1 << page_size_log)" produces an integer rather than long because "1"
> is an int and not long.
My point is that there's no point in using 1ULL because
size_to_hstate() will truncate it anyway.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>