Re: [RFC PATCH 7/9] mm/damon/sysfs-schemes: kobject_del() scheme action destination dirs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Missing `kobject_del()` calls on the error paths of numerous `_add_dirs` initialization loops, leading to delayed-release name conflicts.
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commit 635dc3a5238027dd7ff5a0100c509a12408d26da
Author: SeongJae Park <sj@kernel.org>

mm/damon/sysfs-schemes: kobject_del() scheme action destination dirs

This commit adds kobject_del() calls to the scheme action destination
directories cleanup routine. This prevents directory creation failures
due to name conflicts when CONFIG_DEBUG_KOBJECT_RELEASE is enabled.

> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index 737638be84f15..108f6de32f8c1 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c
> @@ -2148,8 +2148,10 @@ static void damos_sysfs_dests_rm_dirs(
>  	struct damos_sysfs_dest **dests_arr = dests->dests_arr;
>  	int i;
>  
> -	for (i = 0; i < dests->nr; i++)
> +	for (i = 0; i < dests->nr; i++) {
> +		kobject_del(&dests_arr[i]->kobj);
>  		kobject_put(&dests_arr[i]->kobj);
> +	}
>  	dests->nr = 0;
>  	kfree(dests_arr);

[Severity: High]
This is a pre-existing issue, but should the error paths in the various
_add_dirs() functions also be updated to call kobject_del() to prevent the
same name conflicts?

When kobject_init_and_add() succeeds, the kobject is added to sysfs. If a
subsequent initialization step fails, the error paths call kobject_put()
without calling kobject_del() first. Under CONFIG_DEBUG_KOBJECT_RELEASE,
kobject_put() schedules delayed cleanup, so the sysfs directory remains
visible until the delayed release completes. If the user immediately retries,
kobject_init_and_add() will fail with an -EEXIST name collision.

For example, in mm/damon/sysfs.c:damon_sysfs_targets_add_dirs():

        err = kobject_init_and_add(&target->kobj, ...);
        if (err)
                goto out;

        err = damon_sysfs_target_add_dirs(target);
        if (err)
                goto out;

        ...

out:
        damon_sysfs_targets_rm_dirs(targets);
        kobject_put(&target->kobj);
        return err;

Does this series also need to add kobject_del() calls to the error paths
of these functions:
- damon_sysfs_targets_add_dirs() in mm/damon/sysfs.c
- damon_sysfs_probes_add_dirs() in mm/damon/sysfs.c
- damon_sysfs_contexts_add_dirs() in mm/damon/sysfs.c
- damon_sysfs_kdamonds_add_dirs() in mm/damon/sysfs.c
- damon_sysfs_schemes_add_dirs() in mm/damon/sysfs-schemes.c
- damos_sysfs_populate_region_dir() in mm/damon/sysfs-schemes.c

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Sashiko AI review · https://sashiko.dev/#/patchset/20260616150844.88305-1-sj@kernel.org?part=7