Re: [RFC PATCH v1.1 10/11] mm/damon/sysfs: kobject_del() probe dirs in probes_addd_dir error path

[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() in damon_sysfs_schemes_add_dirs() error path causes sysfs name collisions.
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commit 173cb69d781e9cc64949d93111b81f4c2c036934
Author: SeongJae Park <sj@kernel.org>

mm/damon/sysfs: kobject_del() probe dirs in probes_addd_dir error path

This commit fixes a directory creation failure caused by name conflicts
when CONFIG_DEBUG_KOBJECT_RELEASE is enabled. It adds a missing
kobject_del() call to the error handling path of
damon_sysfs_probes_add_dirs() to properly clean up the kobject before
releasing it.

> diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
> index 36a0e82601697..ffbc99411f53b 100644
> --- a/mm/damon/sysfs.c
> +++ b/mm/damon/sysfs.c
> @@ -1183,6 +1183,7 @@ static int damon_sysfs_probes_add_dirs(
>  
>  		err = damon_sysfs_probe_add_dirs(probe);
>  		if (err) {
> +			kobject_del(&probe->kobj);

[Severity: High]
This is a pre-existing issue, but does damon_sysfs_schemes_add_dirs() in
mm/damon/sysfs-schemes.c also need a similar fix?

If kobject_init_and_add() succeeds but the subsequent
damon_sysfs_scheme_add_dirs() fails (e.g., due to -ENOMEM), the error
path jumps to the out label:

out:
	damon_sysfs_schemes_rm_dirs(schemes);
	kobject_put(&scheme->kobj);
	return err;

At this point, damon_sysfs_schemes_rm_dirs() only cleans up previously
fully initialized schemes. The current scheme is not yet part of the array,
so kobject_del() is never called for it. 

When CONFIG_DEBUG_KOBJECT_RELEASE is enabled, kobject_put() delays
memory cleanup. Because kobject_del() wasn't called to unlink it from
sysfs, the lingering kobject can cause a name collision on any subsequent
attempt to write to nr_schemes, preventing further scheme creation until
the delayed release occurs.

Should we add kobject_del(&scheme->kobj) in that error path as well?

>  			kobject_put(&probe->kobj);
>  			damon_sysfs_probes_rm_dirs(probes);
>  			return err;

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Sashiko AI review · https://sashiko.dev/#/patchset/20260617144807.91441-1-sj@kernel.org?part=10