Messages in this thread | | | Date | Thu, 26 May 2022 21:23:22 +0800 | Subject | Re: [PATCH] mm/page_table_check: fix accessing unmapped ptep | From | Qi Zheng <> |
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On 2022/5/26 9:11 PM, Pasha Tatashin wrote: > On Thu, May 26, 2022 at 9:04 AM Qi Zheng <zhengqi.arch@bytedance.com> 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?
My bad, but it's better to call pte_unmap() after the check is done.
> > Pasha > >> >> So: >> >> Reviewed-by: Qi Zheng <zhengqi.arch@bytedance.com> >> >>> >>> Fixes: 80110bbfbba6 ("mm/page_table_check: check entries at pmd levels") >>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> >>> --- >>> 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
-- Thanks, Qi
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