CVE-2026-53342: arm64: mm: call pagetable dtor when freeing hot-removed page tables

CVE-2026-53342: arm64: mm: call pagetable dtor when freeing hot-removed page tables

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

arm64: mm: call pagetable dtor when freeing hot-removed page tables

Since 5e8eb9aeeda3 ("arm64: mm: always call PTE/PMD ctor in
__create_pgd_mapping()") page-table allocation on ARM64 always calls
pagetable_{pte,pmd,pud,p4d}_ctor().  This sets the page_type to
PGTY_table, increments NR_PAGETABLE and possible allocates a PTL.  However
the matching pagetable_dtor() calls were never added.

With DEBUG_VM enabled on kernel versions prior to v6.17 without
2dfcd1608f3a9 ("mm/page_alloc: let page freeing clear any set page type")
this leads to the following warning when freeing these pages due to
page->page_type sharing page->_mapcount:

  BUG: Bad page state in process ... pfn:284fbb
  page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x284fbb
  flags: 0x17fffc000000000(node=0|zone=2|lastcpupid=0x1ffff)
  page_type: f2(table)
  page dumped because: nonzero mapcount
  Call trace:
   bad_page+0x13c/0x160
   __free_frozen_pages+0x6cc/0x860
   ___free_pages+0xf4/0x180
   free_pages+0x54/0x80
   free_hotplug_page_range.part.0+0x58/0x90
   free_empty_tables+0x438/0x500
   __remove_pgd_mapping.constprop.0+0x60/0xa8
   arch_remove_memory+0x48/0x80
   try_remove_memory+0x158/0x1d8
   offline_and_remove_memory+0x138/0x180

It can also lead to leaking the ptl allocation if ALLOC_SPLIT_PTLOCKS is
defined and incorrect NR_PAGETABLE stats.  Fix this by calling
pagetable_dtor() in free_hotplug_pgtable_page() prior to freeing the page
to undo the effects of calling pagetable_*_ctor().

The Linux kernel CVE team has assigned CVE-2026-53342 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.16 with commit 5e8eb9aeeda3a7aaf48efa1d34ae804e894e307f and fixed in 6.18.36 with commit 95f27fcda681021ed3906d3cae7e68b6a57a1d8e
	Issue introduced in 6.16 with commit 5e8eb9aeeda3a7aaf48efa1d34ae804e894e307f and fixed in 7.0.13 with commit aaa688ac9f18207f7452c6472e647c1febaea6a3
	Issue introduced in 6.16 with commit 5e8eb9aeeda3a7aaf48efa1d34ae804e894e307f and fixed in 7.1 with commit c594b83457ccdee76d458416fb3bc9348a37592f

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-53342
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	arch/arm64/mm/mmu.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/95f27fcda681021ed3906d3cae7e68b6a57a1d8e
	https://git.kernel.org/stable/c/aaa688ac9f18207f7452c6472e647c1febaea6a3
	https://git.kernel.org/stable/c/c594b83457ccdee76d458416fb3bc9348a37592f