On 2/1/22 2:02 AM, Pasha Tatashin wrote:
> The pte entry that is used in pte_advanced_tests() is never removed from
> the page table at the end of the test.
>
> The issue is detected by page_table_check, to repro compile kernel with
> the following configs:
>
> CONFIG_DEBUG_VM_PGTABLE=y
> CONFIG_PAGE_TABLE_CHECK=y
> CONFIG_PAGE_TABLE_CHECK_ENFORCED=y
>
> During the boot the following BUG is printed:
>
> [ 2.262821] debug_vm_pgtable: [debug_vm_pgtable ]: Validating
> architecture page table helpers
> [ 2.276826] ------------[ cut here ]------------
> [ 2.280426] kernel BUG at mm/page_table_check.c:162!
> [ 2.284118] invalid opcode: 0000 [#1] PREEMPT SMP PTI
> [ 2.287787] CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> 5.16.0-11413-g2c271fe77d52 #3
> [ 2.293226] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org
> 04/01/2014
> ...
>
> The entry should be properly removed from the page table before the page
> is released to the free list.
>
> Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
> Cc: stable@xxxxxxxxxxxxxxx # 5.9+
Not sure marking stable is necessary here.
>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Tested-by: Zi Yan <ziy@xxxxxxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Dont see any problems on arm64. Although it would be great to run this
on all enabled platforms.
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
> mm/debug_vm_pgtable.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index a7ac97c76762..db2abd9e415b 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -171,6 +171,8 @@ static void __init pte_advanced_tests(struct pgtable_debug_args *args)
> ptep_test_and_clear_young(args->vma, args->vaddr, args->ptep);
> pte = ptep_get(args->ptep);
> WARN_ON(pte_young(pte));
> +
> + ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1);
> }
>
> static void __init pte_savedwrite_tests(struct pgtable_debug_args *args)
>
