[PATCH 5.10 17/74] mm/debug_vm_pgtable: remove pte entry from the page table

[Greg Kroah-Hartman]

From: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>

commit fb5222aae64fe25e5f3ebefde8214dcf3ba33ca5 upstream.

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:

  debug_vm_pgtable: [debug_vm_pgtable         ]: Validating architecture page table helpers
  ------------[ cut here ]------------
  kernel BUG at mm/page_table_check.c:162!
  invalid opcode: 0000 [#1] PREEMPT SMP PTI
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.16.0-11413-g2c271fe77d52 #3
  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@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20220131203249.2832273-2-pasha.tatashin@xxxxxxxxxx
Fixes: a5c3b9ffb0f4 ("mm/debug_vm_pgtable: add tests validating advanced arch page table helpers")
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>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>	[5.9+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/debug_vm_pgtable.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -128,6 +128,8 @@ static void __init pte_advanced_tests(st
 	ptep_test_and_clear_young(vma, vaddr, ptep);
 	pte = ptep_get(ptep);
 	WARN_ON(pte_young(pte));
+
+	ptep_get_and_clear_full(mm, vaddr, ptep, 1);
 }
 
 static void __init pte_savedwrite_tests(unsigned long pfn, pgprot_t prot)