2014-10-22 22:44 GMT+04:00 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>: > 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) > What's wrong? On 32 bits, if page_size_log >= 32, then (unsingned long)(1ULL << page_size_log) will be truncated to 0. I guess it's ok. size_to_hstate will just return NULL in that case. -- Best regards, Andrey Ryabinin -- 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>