PT-2026-64679 · Linux · Linux

CVE-2026-64458

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Publicado

2026-07-25

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Atualizado

2026-07-25

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In the Linux kernel, the following vulnerability has been resolved:
mm/damon/ops-common: handle extreme intervals in damon hot score()
Fix three issues in damon hot score() that comes from wrong handling of extreme (zero or too high) monitoring intervals user setup.
When the user sets sampling interval zero, damon max nr accesses(), which is called from damon hot score(), causes a divide-by-zero. Needless to say, it is a problem.
When the user sets the aggregation interval zero, the function returns zero. It is wrong, since the real maximum nr acceses in the setup should be one. Worse yet, it can cause another divide-by-zero from its caller, damon hot score(), since it uses damon max nr accesses() return value as a denominator.
When the user sets the aggregation interval very high, damon hot score() could return a value out of [0, DAMOS MAX SCORE] range. Since the return value is used as an index to the regions score histogram array, which is DAMOS MAX SCORE+1 size, it causes out of bounds array access.
The issues can be relatively easily reproduced like below. The sysfs write permission is required, though.

./damo start --damos action lru prio --damos quota space 100M

  --damos quota interval 1s

cd /sys/kernel/mm/damon/admin/kdamonds/0

echo 0 > contexts/0/monitoring attrs/intervals/sample us

echo 0 > contexts/0/monitoring attrs/intervals/aggr us

echo commit > state

dmesg

[...] [ 131.329762] Oops: divide error: 0000 [#1] SMP NOPTI [...] [ 131.336089] RIP: 0010:damon hot score+0x27/0xd0 [...]
Fix the divide-by-zero intervals problems by explicitly handling the zero intervals in damon max nr accesses(). Fix the out-of-bound array access by applying [0, DAMOS MAX SCORE] bounds before returning from damon hot score().
The issue was discovered [1] by Sashiko.
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Identificadores relacionados

CVE-2026-64458

Produtos afetados

Linux