Linux Kernel DAMON Div-by-Zero via Zero Quota Target
CVE-2026-99240 Published on November 2, 2026
mm/damon/core: error damos_commit_quota_goal() for zero target_value
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.
Products Associated with CVE-2026-99240
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Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below d5482be6243b816730689099c017109eb8730dd5 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below cc190c4073f570fd78a9d00dd3d13a71eced5403 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 156aeda4d74e9007b56492ed1f3b5838822632be is affected.
- Before 6.18.60 is affected.
- Before 7.2.14 is affected.
- Before 7.3.1 is affected.
- Version 6.18.60, <= 6.18.* is unaffected.
- Version 7.2.14, <= 7.2.* is unaffected.
- Version 7.3.1, <= 7.3.* is unaffected.