From: Pasha Tatashin pasha.tatashin@soleen.com Subject: mm/debug_vm_pgtable: remove pte entry from the page table

Patch series "page table check fixes and cleanups", v5.

This patch (of 4):

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.

Link: https://lkml.kernel.org/r/20220131203249.2832273-1-pasha.tatashin@soleen.com Link: https://lkml.kernel.org/r/20220131203249.2832273-2-pasha.tatashin@soleen.com Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers") Signed-off-by: Pasha Tatashin pasha.tatashin@soleen.com Reviewed-by: Zi Yan ziy@nvidia.com Tested-by: Zi Yan ziy@nvidia.com Acked-by: David Rientjes rientjes@google.com Reviewed-by: Anshuman Khandual anshuman.khandual@arm.com Cc: Paul Turner pjt@google.com Cc: Wei Xu weixugc@google.com Cc: Greg Thelen gthelen@google.com Cc: Ingo Molnar mingo@redhat.com Cc: Will Deacon will@kernel.org Cc: Mike Rapoport rppt@kernel.org Cc: Dave Hansen dave.hansen@linux.intel.com Cc: H. Peter Anvin hpa@zytor.com Cc: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Cc: Jiri Slaby jirislaby@kernel.org Cc: Muchun Song songmuchun@bytedance.com Cc: Hugh Dickins hughd@google.com Cc: stable@vger.kernel.org [5.9+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/debug_vm_pgtable.c | 2 ++ 1 file changed, 2 insertions(+)

--- a/mm/debug_vm_pgtable.c~mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table +++ a/mm/debug_vm_pgtable.c @@ -171,6 +171,8 @@ static void __init pte_advanced_tests(st 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) _