The patch titled Subject: mm/damon/core: avoid divide-by-zero during monitoring results update has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: SeongJae Park sj@kernel.org Subject: mm/damon/core: avoid divide-by-zero during monitoring results update Date: Thu, 19 Oct 2023 19:49:21 +0000

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.

Link: https://lkml.kernel.org/r/20231019194924.100347-3-sj@kernel.org Fixes: 2f5bef5a590b ("mm/damon/core: update monitoring results for new monitoring attributes") Signed-off-by: SeongJae Park sj@kernel.org Cc: stable@vger.kernel.org [6.3+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/damon/core.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update +++ a/mm/damon/core.c @@ -476,20 +476,14 @@ static unsigned int damon_age_for_new_at 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, _

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-implement-a-function-for-max-nr_accesses-safe-calculation.patch mm-damon-core-avoid-divide-by-zero-during-monitoring-results-update.patch mm-damon-ops-common-avoid-divide-by-zero-during-region-hotness-calculation.patch mm-damon-lru_sort-avoid-divide-by-zero-in-hot-threshold-calculation.patch