linux-kernel - [PATCH mm-unstable 2/2] mm/damon/sysfs-schemes: skip schemes regions clearing if the scheme directory has removed

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Date:   Mon, 14 Nov 2022 18:29:54 +0000
From:   SeongJae Park <sj@...nel.org>
To:     SeongJae Park <sj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     damon@...ts.linux.dev, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH mm-unstable 2/2] mm/damon/sysfs-schemes: skip schemes regions clearing if the scheme directory has removed

A DAMON sysfs interface user can start DAMON with a scheme, remove the
sysfs directory for the scheme, and then ask clearing of the scheme's
tried regions.  Because the schemes tried regions clearing logic doesn't
aware of the situation, it results in an invalid memory access.  Fix the
bug by checking if the scheme sysfs directory exists.

Fixes: bb9641eb3a3e ("mm/damon/sysfs-schemes: implement DAMOS-tried regions clear command") # mm-unstable
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 4df3c99983e8..e6baf55d617d 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -1260,6 +1260,10 @@ int damon_sysfs_schemes_clear_regions(
 	damon_for_each_scheme(scheme, ctx) {
 		struct damon_sysfs_scheme *sysfs_scheme;
 
+		/* user could removed the scheme sysfs dir */
+		if (schemes_idx >= sysfs_schemes->nr)
+			break;
+
 		sysfs_scheme = sysfs_schemes->schemes_arr[schemes_idx++];
 		damon_sysfs_scheme_regions_rm_dirs(
 				sysfs_scheme->tried_regions);
-- 
2.25.1