linux-cve-announce - CVE-2025-38442: block: reject bs > ps block devices when THP is disabled

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Message-ID: <2025072502-CVE-2025-38442-2844@gregkh>
Date: Fri, 25 Jul 2025 17:28:04 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38442: block: reject bs > ps block devices when THP is disabled

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

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

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

block: reject bs > ps block devices when THP is disabled

If THP is disabled and when a block device with logical block size >
page size is present, the following null ptr deref panic happens during
boot:

[   [13.2 mK  AOSAN: null-ptr-deref in range [0x0000000000000000-0x0000000000K0 0 0[07]
[   13.017749] RIP: 0010:create_empty_buffers+0x3b/0x380
<snip>
[   13.025448] Call Trace:
[   13.025692]  <TASK>
[   13.025895]  block_read_full_folio+0x610/0x780
[   13.026379]  ? __pfx_blkdev_get_block+0x10/0x10
[   13.027008]  ? __folio_batch_add_and_move+0x1fa/0x2b0
[   13.027548]  ? __pfx_blkdev_read_folio+0x10/0x10
[   13.028080]  filemap_read_folio+0x9b/0x200
[   13.028526]  ? __pfx_filemap_read_folio+0x10/0x10
[   13.029030]  ? __filemap_get_folio+0x43/0x620
[   13.029497]  do_read_cache_folio+0x155/0x3b0
[   13.029962]  ? __pfx_blkdev_read_folio+0x10/0x10
[   13.030381]  read_part_sector+0xb7/0x2a0
[   13.030805]  read_lba+0x174/0x2c0
<snip>
[   13.045348]  nvme_scan_ns+0x684/0x850 [nvme_core]
[   13.045858]  ? __pfx_nvme_scan_ns+0x10/0x10 [nvme_core]
[   13.046414]  ? _raw_spin_unlock+0x15/0x40
[   13.046843]  ? __switch_to+0x523/0x10a0
[   13.047253]  ? kvm_clock_get_cycles+0x14/0x30
[   13.047742]  ? __pfx_nvme_scan_ns_async+0x10/0x10 [nvme_core]
[   13.048353]  async_run_entry_fn+0x96/0x4f0
[   13.048787]  process_one_work+0x667/0x10a0
[   13.049219]  worker_thread+0x63c/0xf60

As large folio support depends on THP, only allow bs > ps block devices
if THP is enabled.

The Linux kernel CVE team has assigned CVE-2025-38442 to this issue.


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

	Issue introduced in 6.15 with commit 47dd67532303803a87f43195e088b3b4bcf0454d and fixed in 6.15.7 with commit b025d81b96bfe8a62b6e3e6ac776608206ccbf6d
	Issue introduced in 6.15 with commit 47dd67532303803a87f43195e088b3b4bcf0454d and fixed in 6.16-rc6 with commit 4cdf1bdd45ac78a088773722f009883af30ad318

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-2025-38442
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:
	include/linux/blkdev.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/b025d81b96bfe8a62b6e3e6ac776608206ccbf6d
	https://git.kernel.org/stable/c/4cdf1bdd45ac78a088773722f009883af30ad318