linux-kernel - [PATCH] mm/damon/sysfs-schemes: handle schemes sysfs dir removal before commit_schemes_quota

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Message-Id: <20240213023633.124928-1-sj@kernel.org>
Date: Mon, 12 Feb 2024 18:36:32 -0800
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] mm/damon/sysfs-schemes: handle schemes sysfs dir removal before commit_schemes_quota_goals

'commit_schemes_quota_goals' command handler,
damos_sysfs_set_quota_scores() assumes the number of schemes sysfs
directory will be same to the number of schemes of the DAMON context.
The assumption is wrong since users can remove schemes sysfs directories
while DAMON is running.  In the case, illegal memory accesses can
happen.  Fix it by checking the case.

Fixes: d91beaa505a0 ("mm/damon/sysfs-schemes: implement a command for scheme quota goals only commit")
Signed-off-by: SeongJae Park <sj@...nel.org>
---
 mm/damon/sysfs-schemes.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 98c6e5376486..f6c7f43f06cc 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1905,6 +1905,10 @@ void damos_sysfs_set_quota_scores(struct damon_sysfs_schemes *sysfs_schemes,
 	damon_for_each_scheme(scheme, ctx) {
 		struct damon_sysfs_scheme *sysfs_scheme;
 
+		/* user could have removed the scheme sysfs dir */
+		if (i >= sysfs_schemes->nr)
+			break;
+
 		sysfs_scheme = sysfs_schemes->schemes_arr[i];
 		damos_sysfs_set_quota_score(sysfs_scheme->quotas->goals,
 				&scheme->quota);
-- 
2.39.2