From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89644: btrfs: fix extent map leak in NOCOW direct I/O write
Date: Fri, 11 Sep 2026 21:45:33 +0200 [thread overview]
Message-ID: <2026091142-CVE-2026-89644-f0cd@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix extent map leak in NOCOW direct I/O write
btrfs_dio_iomap_begin() calls btrfs_get_extent(), which returns an
extent map reference that must be dropped on all exit paths.
For direct writes into a NOCOW range, btrfs_get_blocks_direct_write()
keeps using that extent map and asks btrfs_create_dio_extent() to
allocate the ordered extent. If that fails, for example because
btrfs_alloc_ordered_extent() fails, the function returns the error
without dropping the input extent map. The PREALLOC path avoided this by
dropping the input extent map before replacing it with the newly created
one.
Check the error from btrfs_create_dio_extent() before replacing the
map and drop the input extent map on failure.
The Linux kernel CVE team has assigned CVE-2026-89644 to this issue.
Affected and fixed versions
===========================
Issue introduced in 4.7 with commit 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af and fixed in 6.18.50 with commit f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2
Issue introduced in 4.7 with commit 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af and fixed in 7.2.4 with commit 05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d
Issue introduced in 4.7 with commit 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af and fixed in 7.3-rc1 with commit 3f950867c307c5413d628a153ac44915bd117ffd
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-2026-89644
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/direct-io.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/f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2
https://git.kernel.org/stable/c/05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d
https://git.kernel.org/stable/c/3f950867c307c5413d628a153ac44915bd117ffd
reply other threads:[~2026-09-11 20:00 UTC|newest]
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