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SubjectRe: [PATCH v2] hugetlb: clean up potential spectre issue warnings
On Wed 23-02-22 10:36:55, Mike Kravetz wrote:
> On 2/23/22 00:33, Michal Hocko wrote:
> > On Tue 22-02-22 13:53:56, Mike Kravetz wrote:
> >> On 2/21/22 23:47, Michal Hocko wrote:
> >> How about adding this note to the commit message?
> >>
> >> Note: these routines take a user specified value used as an index ONCE
> >> during the boot process. As a result, they can not be used as a general
> >> method of exploitation. Code changes are being made to eliminate warnings.
> >
> > This would help but the question whether the change is worth remains.
> > Does this change have any other advantage than silencing the warning?
> >
>
> Silencing the warnings was the primary motivation for the change. If Dan
> has a plan to change smatch so that they are silenced for __init functions,
> then it would be better to not make the changes to use array_index_nospec.
>
> While making the changes, I shuffled the code a little and did not immediately
> notice that it also 'fixes' an overflow/truncation issue when assigning an
> unsigned long to int as addressed in [1]. We should probably make this change
> whether or not we use array_index_nospec to silence warnings.
>
> [1] https://lore.kernel.org/linux-mm/20220209134018.8242-1-liuyuntao10@huawei.com/

Yeah, this makes sense to me.
--
Michal Hocko
SUSE Labs

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