Messages in this thread | | | Date | Thu, 26 May 2022 21:04:52 +0800 | Subject | Re: [PATCH] mm/page_table_check: fix accessing unmapped ptep | From | Qi Zheng <> |
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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.
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
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