On Thu, May 26, 2022 at 9:04 AM Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
>
>
>
> On 2022/5/26 7:33 PM, Miaohe Lin wrote:
> > ptep is unmapped too early, so ptep will be accessed while it's unmapped.
> > Fix it by deferring pte_unmap() until page table checking is done.
>
> In the beginning, page_table_check only supported x86_64, so there
> is no problem. But then the commit 3fee229a8eb9 ("riscv/mm: enable
> ARCH_SUPPORTS_PAGE_TABLE_CHECK") added support for riscv-32, it is
> indeed a problem in this case.
pte_unmap() is needed only with CONFIG_HIGHPTE. I do not see this
config for riskv-32?
Pasha
>
> So:
>
> Reviewed-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
>
> >
> > Fixes: 80110bbfbba6 ("mm/page_table_check: check entries at pmd levels")
> > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> > ---
> > mm/page_table_check.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/page_table_check.c b/mm/page_table_check.c
> > index 3692bea2ea2c..971c3129b0e3 100644
> > --- a/mm/page_table_check.c
> > +++ b/mm/page_table_check.c
> > @@ -234,11 +234,11 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm,
> > pte_t *ptep = pte_offset_map(&pmd, addr);
> > unsigned long i;
> >
> > - pte_unmap(ptep);
> > for (i = 0; i < PTRS_PER_PTE; i++) {
> > __page_table_check_pte_clear(mm, addr, *ptep);
> > addr += PAGE_SIZE;
> > ptep++;
> > }
> > + pte_unmap(ptep);
> > }
> > }
>
> --
> Thanks,
> Qi
