Re: [PATCH v5 1/2] mm/damon/core: prevent size quota overflow in the temporal goal tuner

[sashiko-bot@kernel.org]

> From: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
> 
> damos_goal_tune_esz_bp_temporal() converts the scheme's size quota
> into basis points with "quota->esz_bp = quota->sz * 10000", both
> unsigned long, and damos_set_effective_quota() divides the result
> back by 10000.  quotas/bytes is unbounded; bytes_store() hands it to
> kstrtoul() as is.
> 
> On 32-bit the product wraps for any size quota above ULONG_MAX /
> 10000, that is 429496 bytes.  A wrapped product below 10000 divides
> to a zero effective quota: 429497 gives 0.  damos_quota_is_full() is
> then true on the first test of every charge window.  Other wrapped
> values are wrong without being zero: 500000 gives 70503.
> 
> Triggering this needs a scheme with a quota goal, the temporal goal
> [ ... ]
> Fixes: af738a6a00c1 ("mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL")
> Cc: <stable@vger.kernel.org> # 7.1.x
> Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
> Reviewed-by: SJ Park <sj@kernel.org>
> Signed-off-by: SJ Park <sj@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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