Bug 2565287 (CVE-2026-99240)

Summary: CVE-2026-99240 kernel: kernel: Denial of Service via division by zero in DAMON subsystem
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Data Access Monitor (DAMON) subsystem. A local user can trigger a division-by-zero error by configuring a monitoring scheme with a quota target value of zero. This failure can cause the kernel to crash, resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-11-02 17:05:11 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm/damon/core: error damos_commit_quota_goal() for zero target_value

Patch series "mm/damon: move zero damos quota target_value handling to the
core layer".

Having zero DAMOS quota target value can cause division by zero.  DAMON
API callers are checking the target value parameters to avoid that.  It is
easy to make mistakes in some of the multiple API callers.  Move that to
the core layer.

Patch 1 adds the corner case handling into the core layer DAMON parameters
validation logic.  Patches 2 and 3 remove no more needed DAMON API callers
side handling of the corner case in DAMON_LRU_SORT and DMON_SAMPLIE_MTIER,
respectively.


This patch (of 3):

If a DAMOS scheme has a damos_quota_goal of zero target_value,
damos_quota_goal() could trigger division-by-zero error.  Hence each DAMON
API callers should do the zero target_value validation.  It is easy to
make mistakes.  Actually such bugs in DAMON_LRU_SORT and
DAMON_SAMPLE_MTIER were found and fixed [1].

It is better to handle the corner case only once in the core layer,
instead of multiple places in all DAMON API callers.  One straightforward
option is using an alternative denominator for the corner case in the
damos_quota_goal().  However, the zero target_value is meaningless.  In
this case, the quota goal is always evaluated as achieved or
over-achieved.  The quota will only keep being reduced.

Simply avoid using zero target_value by adding a check in the core layer
DAMOS quota goal parameters validation/commit path,
damos_commit_quota_goal().  Update it to return an error in the case. 
Also update its caller to propagate the error.