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mm/page_table_check: fix accessing unmapped ptep

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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 <linmiaohe@huawei.com>
Acked-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Miaohe Lin 2022-05-26 19:33:50 +08:00 committed by akpm
parent 3e35142ef9
commit 24c8e27e63
1 changed files with 1 additions and 1 deletions
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2
mm/page_table_check.c
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@ -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);
}
}