+ mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write.patch added to mm-hotfixes-unstable branch

+ mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/sysfs-schemes: free old damon_sysfs_scheme_filter->memcg_path on write
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write.patch

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/sysfs-schemes: free old damon_sysfs_scheme_filter->memcg_path on write
Date: Thu, 19 Jun 2025 11:36:07 -0700

memcg_path_store() assigns a newly allocated memory buffer to
filter->memcg_path, without deallocating the previously allocated and
assigned memory buffer.  As a result, users can leak kernel memory by
continuously writing a data to memcg_path DAMOS sysfs file.  Fix the leak
by deallocating the previously set memory buffer.

Link: https://lkml.kernel.org/r/20250619183608.6647-2-sj@kernel.org
Fixes: 7ee161f18b5d ("mm/damon/sysfs-schemes: implement filter directory")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>		[6.3.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/sysfs-schemes.c |    1 +
 1 file changed, 1 insertion(+)

--- a/mm/damon/sysfs-schemes.c~mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write
+++ a/mm/damon/sysfs-schemes.c
@@ -472,6 +472,7 @@ static ssize_t memcg_path_store(struct k
 		return -ENOMEM;
 
 	strscpy(path, buf, count + 1);
+	kfree(filter->memcg_path);
 	filter->memcg_path = path;
 	return count;
 }
_

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

mm-damon-sysfs-schemes-free-old-damon_sysfs_scheme_filter-memcg_path-on-write.patch
mm-damon-introduce-damon_stat-module.patch
mm-damon-introduce-damon_stat-module-fix.patch
mm-damon-stat-calculate-and-expose-estimated-memory-bandwidth.patch
mm-damon-stat-calculate-and-expose-idle-time-percentiles.patch
docs-admin-guide-mm-damon-add-damon_stat-usage-document.patch
mm-damon-paddr-use-alloc_migartion_target-with-no-migration-fallback-nodemask.patch
revert-mm-rename-alloc_demote_folio-to-alloc_migrate_folio.patch
revert-mm-make-alloc_demote_folio-externally-invokable-for-migration.patch
selftets-damon-add-a-test-for-memcg_path-leak.patch