linux-cve-announce - CVE-2025-21907: mm: memory-failure: update ttu flag inside unmap_poisoned

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Message-ID: <2025040129-CVE-2025-21907-5379@gregkh>
Date: Tue,  1 Apr 2025 16:39:31 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21907: mm: memory-failure: update ttu flag inside unmap_poisoned_folio

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

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

mm: memory-failure: update ttu flag inside unmap_poisoned_folio

Patch series "mm: memory_failure: unmap poisoned folio during migrate
properly", v3.

Fix two bugs during folio migration if the folio is poisoned.


This patch (of 3):

Commit 6da6b1d4a7df ("mm/hwpoison: convert TTU_IGNORE_HWPOISON to
TTU_HWPOISON") introduce TTU_HWPOISON to replace TTU_IGNORE_HWPOISON in
order to stop send SIGBUS signal when accessing an error page after a
memory error on a clean folio.  However during page migration, anon folio
must be set with TTU_HWPOISON during unmap_*().  For pagecache we need
some policy just like the one in hwpoison_user_mappings to set this flag. 
So move this policy from hwpoison_user_mappings to unmap_poisoned_folio to
handle this warning properly.

Warning will be produced during unamp poison folio with the following log:

  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 365 at mm/rmap.c:1847 try_to_unmap_one+0x8fc/0xd3c
  Modules linked in:
  CPU: 1 UID: 0 PID: 365 Comm: bash Tainted: G        W          6.13.0-rc1-00018-gacdb4bbda7ab #42
  Tainted: [W]=WARN
  Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
  pstate: 20400005 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : try_to_unmap_one+0x8fc/0xd3c
  lr : try_to_unmap_one+0x3dc/0xd3c
  Call trace:
   try_to_unmap_one+0x8fc/0xd3c (P)
   try_to_unmap_one+0x3dc/0xd3c (L)
   rmap_walk_anon+0xdc/0x1f8
   rmap_walk+0x3c/0x58
   try_to_unmap+0x88/0x90
   unmap_poisoned_folio+0x30/0xa8
   do_migrate_range+0x4a0/0x568
   offline_pages+0x5a4/0x670
   memory_block_action+0x17c/0x374
   memory_subsys_offline+0x3c/0x78
   device_offline+0xa4/0xd0
   state_store+0x8c/0xf0
   dev_attr_store+0x18/0x2c
   sysfs_kf_write+0x44/0x54
   kernfs_fop_write_iter+0x118/0x1a8
   vfs_write+0x3a8/0x4bc
   ksys_write+0x6c/0xf8
   __arm64_sys_write+0x1c/0x28
   invoke_syscall+0x44/0x100
   el0_svc_common.constprop.0+0x40/0xe0
   do_el0_svc+0x1c/0x28
   el0_svc+0x30/0xd0
   el0t_64_sync_handler+0xc8/0xcc
   el0t_64_sync+0x198/0x19c
  ---[ end trace 0000000000000000 ]---

[mawupeng1@...wei.com: unmap_poisoned_folio(): remove shadowed local `mapping', per Miaohe]
  Link: https://lkml.kernel.org/r/20250219060653.3849083-1-mawupeng1@huawei.com

The Linux kernel CVE team has assigned CVE-2025-21907 to this issue.


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

	Issue introduced in 6.3 with commit 6da6b1d4a7df8c35770186b53ef65d388398e139 and fixed in 6.12.19 with commit 608cc7deb428f1122ed426060233622ebf667b6e
	Issue introduced in 6.3 with commit 6da6b1d4a7df8c35770186b53ef65d388398e139 and fixed in 6.13.7 with commit 425c12c076e6fc6b2cb04b9f960319d31dcabc76
	Issue introduced in 6.3 with commit 6da6b1d4a7df8c35770186b53ef65d388398e139 and fixed in 6.14 with commit b81679b1633aa43c0d973adfa816d78c1ed0d032
	Issue introduced in 6.1.16 with commit deab8114fb67dcb0e6293b665c3c7083fbadff17
	Issue introduced in 6.2.3 with commit 6dcf132fe236045bd7f50c008660ea086d09af1f

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-2025-21907
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:
	mm/internal.h
	mm/memory-failure.c
	mm/memory_hotplug.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/608cc7deb428f1122ed426060233622ebf667b6e
	https://git.kernel.org/stable/c/425c12c076e6fc6b2cb04b9f960319d31dcabc76
	https://git.kernel.org/stable/c/b81679b1633aa43c0d973adfa816d78c1ed0d032