From 24c8e27e63224ce832b4723cb60632d3eddb55de Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Thu, 26 May 2022 19:33:50 +0800 Subject: mm/page_table_check: fix accessing unmapped ptep ptep is unmapped too early, so ptep could theoretically be accessed while it's unmapped. This might become a problem if/when CONFIG_HIGHPTE becomes available on riscv. Fix it by deferring pte_unmap() until page table checking is done. [akpm@linux-foundation.org: account for ptep alteration, per Matthew] Link: https://lkml.kernel.org/r/20220526113350.30806-1-linmiaohe@huawei.com Fixes: 80110bbfbba6 ("mm/page_table_check: check entries at pmd levels") Signed-off-by: Miaohe Lin Acked-by: Pasha Tatashin Cc: Qi Zheng Cc: Matthew Wilcox Cc: David Rientjes Signed-off-by: Andrew Morton --- 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 2458281bff89..bc55be28807f 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -251,11 +251,11 @@ 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 - PTRS_PER_PTE); } } -- cgit v1.2.3