CVE-2026-90391

What the bug is

dmirror_fault() is called from the dmirror_read() and dmirror_write() retry loops after dmirror_do_read() or dmirror_do_write() finds a missing device page table entry. If the mirrored mm has already exited, mmget_not_zero() fails. The current code returns 0 in that case, which tells the caller that faulting succeeded even though no page was faulted and no device page table entry was installed. The caller then retries the same address, hits -ENOENT again, and can loop forever without making progress. Return -EFAULT instead, so the ioctl fails when the mirrored mm is no longer faultable.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

lib/test_hmm.c

What this is

HMM - Heterogeneous Memory ManagementMAINTAINERS section matched on lib/test_hmm* · linux-mm@kvack.org · Maintained

Kernel module

none to look for. The file would have gone into test_hmm, and Debian does not compile it into that module, so finding test_hmm in lsmod would say nothing about this CVE.

Check it on the machine

grep -w CONFIG_TEST_HMM /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sid, bookworm · linux-6.12n

n

not enabled on any flavour - this release does not build the code

Build switch

CONFIG_TEST_HMM

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-09-17 (31 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.21%, higher than 10.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

lib

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.8	5.10.270	50606ced3037
5.8	5.15.221	541a67f21ab8
5.8	6.1.188	d8e64ffab01e
5.8	6.6.157	2636569ea7c1
5.8	6.12.110	701347e31aa6
5.8	6.18.52	af7a6d6ec36a
5.8	7.2.6	a2074f86fc96
5.8	7.3	6a8024511ddf

Debian advisories