CVE-2026-89796

What the bug is

Patch series "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races", v1.1. Sashiko found a few issues in DAMON that could cause infinite loop, NULL dereference and monitoring results degradation. The first two sounds scary but the infinite loop happens only under unreasonable user setup. The NULL dereference is only in a unit test. Monitoring results degradation is trivial since it is only best-effort, and those happens from only unlikely races. Still those are bugs that better to fix if possible. Fix those. This patch (of 6): Due to online parameter update like events, the number of DAMON regions could be higher than the user-set upper limit. kdamond_merge_regions() repeats merge regions until the number meets the limit, while doubling the merge threshold up to the theoretical maximum threshold. It is tried only up to the theoretical maximum threshold because even the aggressive merging can fail from reducing the number of regions under the user-defined upper limit. For example, there could be many user-defined non-contiguous regions that cannot be merged. The threshold based loop break condition is evaluated by comparing the threshold for the next merging try against the theoretical maximum threshold. If max_thres is larger than UINT_MAX / 2, doubling the threshold could make it overflow, and bypass the loop break condition. In the case, if the number of regions cannot be reduced under the upper limit like explained above, the loop will run infinitely. Prevent the case by doing the break condition check before doubling the threshold. Also, prevent the threshold exceeding the maximum threshold, as it could overflow and apply the wrong merge threshold. This issue is unlikely to occur in real world, since having the max_thres higher than UINT_MAX / 2 require unrealistically large aggregation intervals compared to the sampling interval. Also, it requires an unrealistically large number of uncontiguous regions setup. Nonetheless, the consequence is bad and the fix is simple. The issue was discovered [1] by Sashiko.

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.

mm/damon/core.c

What this is

DAMONMAINTAINERS section matched on mm/damon/ · damon@lists.linux.dev · Maintained

Check it on the machine

grep -w CONFIG_DAMON /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 1 release. It does build it in 4 releases, so the answer depends on which release the machine runs.

• bookwormn
• trixie, forky, sid, bookworm · linux-6.12y

n

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

y

built into the kernel image on every flavour - only a patch removes it

Build switch

CONFIG_DAMON

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

2026-09-16 (33 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.22%, higher than 12.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

mm/damon

Upstream fixes

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

Introduced	Fixed in	Commit
5.15.164	5.15.222	407da1dd7f48
6.1.101	6.1.189	65edd8b3a882
6.6.41	6.6.158	5b0953f86d65
6.10	6.12.111	769c16699c89
6.10	6.18.53	50a7a5aec1aa
6.10	7.2.5	8a96a06e04d2
6.10	7.3	123e4619ab6c
6.9.10	0	0

Debian advisories