linux-cve-announce - CVE-2022-49778: arm64/mm: fix incorrect file_map

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Message-ID: <2025050118-CVE-2022-49778-ea15@gregkh>
Date: Thu,  1 May 2025 16:09:28 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2022-49778: arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud

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

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

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

arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud

The page table check trigger BUG_ON() unexpectedly when collapse hugepage:

 ------------[ cut here ]------------
 kernel BUG at mm/page_table_check.c:82!
 Internal error: Oops - BUG: 00000000f2000800 [#1] SMP
 Dumping ftrace buffer:
    (ftrace buffer empty)
 Modules linked in:
 CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750
 Hardware name: linux,dummy-virt (DT)
 pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 pc : page_table_check_clear.isra.0+0x258/0x3f0
 lr : page_table_check_clear.isra.0+0x240/0x3f0
[...]
 Call trace:
  page_table_check_clear.isra.0+0x258/0x3f0
  __page_table_check_pmd_clear+0xbc/0x108
  pmdp_collapse_flush+0xb0/0x160
  collapse_huge_page+0xa08/0x1080
  hpage_collapse_scan_pmd+0xf30/0x1590
  khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8
  khugepaged+0x338/0x518
  kthread+0x278/0x2f8
  ret_from_fork+0x10/0x20
[...]

Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it
decrease file_map_count for a non-leaf pmd comes from collapse_huge_page().
and so trigger BUG_ON() unexpectedly.

Fix this problem by using pmd_leaf() insteal of pmd_present() in
pmd_user_accessible_page(). Moreover, use pud_leaf() for
pud_user_accessible_page() too.

The Linux kernel CVE team has assigned CVE-2022-49778 to this issue.


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

	Issue introduced in 5.19 with commit 42b2547137f5c974bb1bfd657c869fe96b96d86f and fixed in 6.0.10 with commit 2d458046df634088611d44fd77f45465e833ef78
	Issue introduced in 5.19 with commit 42b2547137f5c974bb1bfd657c869fe96b96d86f and fixed in 6.1 with commit 5b47348fc0b18a78c96f8474cc90b7525ad1bbfe

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-2022-49778
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/include/asm/pgtable.h


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/2d458046df634088611d44fd77f45465e833ef78
	https://git.kernel.org/stable/c/5b47348fc0b18a78c96f8474cc90b7525ad1bbfe