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

[SeongJae Park <sj@kernel.org>]

On Tue, 16 Jun 2026 15:34:09 +0000 sashiko-bot@kernel.org wrote:

> 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.
> --
> 
> 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

Yes.  Sashiko reported same issue in other replies to this thread and I
promised to fix these in the next revision.


Thanks,
SJ

[...]