CVE-2026-98161: nvdimm: pmem: keep PREFLUSH before data writes

CVE-2026-98161: nvdimm: pmem: keep PREFLUSH before data writes

[Greg Kroah-Hartman]

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

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

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

nvdimm: pmem: keep PREFLUSH before data writes

pmem_submit_bio() records a REQ_PREFLUSH error, but continues to copy the
bio data and can later overwrite the error with a successful REQ_FUA flush.
That lets data writes run after a failed preflush and can complete the bio
successfully despite the failed ordering barrier.

Run the REQ_PREFLUSH flush synchronously before touching the bio data and
complete the bio with the flush error if it fails. Keep asynchronous flush
chaining for REQ_FUA. At that point, data copy has completed and the parent
bio can wait for the chained flush bio.

The Linux kernel CVE team has assigned CVE-2026-98161 to this issue.


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

	Fixed in 6.18.52 with commit 770a90c2127220f0fc194ce909ad4f0842e141cb
	Fixed in 7.2.6 with commit 72561ca1ab96f0f0f32737a6171641e05a318538
	Fixed in 7.3-rc1 with commit c644a2f8fef5618fcf453c591177700fd07dd024

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-2026-98161
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:
	drivers/nvdimm/pmem.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/770a90c2127220f0fc194ce909ad4f0842e141cb
	https://git.kernel.org/stable/c/72561ca1ab96f0f0f32737a6171641e05a318538
	https://git.kernel.org/stable/c/c644a2f8fef5618fcf453c591177700fd07dd024