CVE-2026-93076: dax/fsdev: clear vmemmap_shift when binding static pgmap

CVE-2026-93076: dax/fsdev: clear vmemmap_shift when binding static pgmap

[Greg Kroah-Hartman]

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

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

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

dax/fsdev: clear vmemmap_shift when binding static pgmap

Clear pgmap->vmemmap_shift for static DAX devices. When rebinding a static
device from device_dax (which may set vmemmap_shift based on alignment) to
fsdev_dax, the stale vmemmap_shift persists on the shared pgmap. Explicitly
zero it before devm_memremap_pages() so the vmemmap is built for order-0
folios as fsdev requires.

The Linux kernel CVE team has assigned CVE-2026-93076 to this issue.


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

	Issue introduced in 7.1 with commit d5406bd458b0ac10b1301a4d5801d85c8f648637 and fixed in 7.2.6 with commit d298a0513aaf7d48f2a9f4a90041de910750cfcf
	Issue introduced in 7.1 with commit d5406bd458b0ac10b1301a4d5801d85c8f648637 and fixed in 7.3-rc1 with commit e0239229931faf9ca3367e3befcf16f77b2cd45b

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-2026-93076
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/dax/fsdev.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/d298a0513aaf7d48f2a9f4a90041de910750cfcf
	https://git.kernel.org/stable/c/e0239229931faf9ca3367e3befcf16f77b2cd45b