mm/damon/sysfs-schemes: handle schemes sysfs dir removal before commit_schemes_quota_...

'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.

Link: https://lkml.kernel.org/r/20240213023633.124928-1-sj@kernel.org
Fixes: d91beaa505a0 ("mm/damon/sysfs-schemes: implement a command for scheme quota goals only commit")
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index dd2fb512700920803b10621b82ffaa88bff30a92..ae0f0b314f3a9a5ec251021d0fb68d423fa53cd7 100644 (file)
--- 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);