linux-kernel - [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <20231020172317.64192-6-sj@kernel.org>
Date:   Fri, 20 Oct 2023 17:23:17 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     SeongJae Park <sj@...nel.org>, damon@...ts.linux.dev,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] mm/damon/core: avoid divide-by-zero from pseudo-moving window length calculation

When calculating the pseudo-moving access rate, DAMON 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.

Note that this is a fix for a commit that not in the mainline but mm
tree.

Fixes: ace30fb21af5 ("mm/damon/core: use pseudo-moving sum for nr_accesses_bp")
Signed-off-by: SeongJae Park <sj@...nel.org>
---

Note that this is for a patch in mm-stable that not yet merged into the
mainline.

 mm/damon/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index e194c8075235..aa2dc7087cd9 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -1665,7 +1665,7 @@ void damon_update_region_access_rate(struct damon_region *r, bool accessed,
 	 * aggr_interval, owing to validation of damon_set_attrs().
 	 */
 	if (attrs->sample_interval)
-		len_window = attrs->aggr_interval / attrs->sample_interval;
+		len_window = damon_max_nr_accesses(attrs);
 	r->nr_accesses_bp = damon_moving_sum(r->nr_accesses_bp,
 			r->last_nr_accesses * 10000, len_window,
 			accessed ? 10000 : 0);
-- 
2.34.1