+ mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/debug_vm_pgtable: remove pte entry from the page table
has been added to the -mm tree.  Its filename is
     mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table.patch

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------------------------------------------------------
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", v4.

Two fixes:

  mm/debug_vm_pgtable: remove pte entry from the page table
	- remove a pte entry from the page table at the end of
	  debug_vm_pgtable pte test

  mm/khugepaged: unify collapse pmd clear, flush and free
  mm/page_table_check: check entries at pmd levels
	- check pmd level in page_table_check for PTE regular entries
	  prior to freeing.
	  repro.c: https://gist.github.com/soleen/fdcd501d5df103976245fe84e9535087
	  config: https://gist.github.com/soleen/8a56f923c2fea9ce9c75b4e2517d4162
	  qemu_script: https://gist.github.com/soleen/f4be4795826b7ab1a51ae659582e179c
	  base image:
	  https://storage.googleapis.com/syzkaller/wheezy.img
	  https://storage.googleapis.com/syzkaller/wheezy.img.key

Small cleanup:
  mm/page_table_check: use unsigned long for page counters and cleanup


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/20220126183637.1840960-2-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>
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: Anshuman Khandual <anshuman.khandual@arm.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)
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

mm-debug_vm_pgtable-remove-pte-entry-from-the-page-table.patch
mm-page_table_check-use-unsigned-long-for-page-counters-and-cleanup.patch
mm-khugepaged-unify-collapse-pmd-clear-flush-and-free.patch
mm-page_table_check-check-entries-at-pmd-levels.patch