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    Subject[PATCH v2 2/5] mm/damon/core: avoid divide-by-zero during monitoring results update
    Date
    When monitoring attributes are changed, DAMON updates access rate of the
    monitoring results accordingly. For that, it divides some values by the
    maximum nr_accesses. However, due to the type of the related variables,
    simple division-based calculation of the divisor can return zero. As a
    result, divide-by-zero is possible. Fix it by using
    damon_max_nr_accesses(), which handles the case.

    Reported-by: Jakub Acs <acsjakub@amazon.de>
    Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new monitoring attributes")
    Cc: <stable@vger.kernel.org> # 6.3.x
    Signed-off-by: SeongJae Park <sj@kernel.org>
    ---
    mm/damon/core.c | 10 ++--------
    1 file changed, 2 insertions(+), 8 deletions(-)

    diff --git a/mm/damon/core.c b/mm/damon/core.c
    index 9f4f7c378cf3..e194c8075235 100644
    --- a/mm/damon/core.c
    +++ b/mm/damon/core.c
    @@ -500,20 +500,14 @@ static unsigned int damon_age_for_new_attrs(unsigned int age,
    static unsigned int damon_accesses_bp_to_nr_accesses(
    unsigned int accesses_bp, struct damon_attrs *attrs)
    {
    - unsigned int max_nr_accesses =
    - attrs->aggr_interval / attrs->sample_interval;
    -
    - return accesses_bp * max_nr_accesses / 10000;
    + return accesses_bp * damon_max_nr_accesses(attrs) / 10000;
    }

    /* convert nr_accesses to access ratio in bp (per 10,000) */
    static unsigned int damon_nr_accesses_to_accesses_bp(
    unsigned int nr_accesses, struct damon_attrs *attrs)
    {
    - unsigned int max_nr_accesses =
    - attrs->aggr_interval / attrs->sample_interval;
    -
    - return nr_accesses * 10000 / max_nr_accesses;
    + return nr_accesses * 10000 / damon_max_nr_accesses(attrs);
    }

    static unsigned int damon_nr_accesses_for_new_attrs(unsigned int nr_accesses,
    --
    2.34.1
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