linux-cve-announce - CVE-2026-23147: btrfs: zlib: fix the folio leak on S390 hardware acceleration

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Message-ID: <2026021413-CVE-2026-23147-1f6d@gregkh>
Date: Sat, 14 Feb 2026 17:04:13 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23147: btrfs: zlib: fix the folio leak on S390 hardware acceleration

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

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

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

btrfs: zlib: fix the folio leak on S390 hardware acceleration

[BUG]
After commit aa60fe12b4f4 ("btrfs: zlib: refactor S390x HW acceleration
buffer preparation"), we no longer release the folio of the page cache
of folio returned by btrfs_compress_filemap_get_folio() for S390
hardware acceleration path.

[CAUSE]
Before that commit, we call kumap_local() and folio_put() after handling
each folio.

Although the timing is not ideal (it release previous folio at the
beginning of the loop, and rely on some extra cleanup out of the loop),
it at least handles the folio release correctly.

Meanwhile the refactored code is easier to read, it lacks the call to
release the filemap folio.

[FIX]
Add the missing folio_put() for copy_data_into_buffer().

The Linux kernel CVE team has assigned CVE-2026-23147 to this issue.

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

	Issue introduced in 6.15 with commit aa60fe12b4f49f49fc73e5023f8675e2df1f7805 and fixed in 6.18.9 with commit e80617a5e1c246da2f112a1a072cdd535046adfe
	Issue introduced in 6.15 with commit aa60fe12b4f49f49fc73e5023f8675e2df1f7805 and fixed in 6.19 with commit 0d0f1314e8f86f5205f71f9e31e272a1d008e40b

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-2026-23147
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:
	fs/btrfs/zlib.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/e80617a5e1c246da2f112a1a072cdd535046adfe
	https://git.kernel.org/stable/c/0d0f1314e8f86f5205f71f9e31e272a1d008e40b