On 2022/5/26 9:11 PM, Pasha Tatashin wrote:
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?
My bad, but it's better to call pte_unmap() after the check is done.
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
--
Thanks,
Qi
