Re: [PATCH] mm/slub: fix kobject leak in sysfs_slab_add error path

[Hongling Zeng]

在 2026年07月13日 14:27, Harry Yoo 写道:
> On 7/13/26 3:14 PM, Hongling Zeng wrote:
> > 在 2026年07月13日 14:07, Harry Yoo 写道:
> > > On 7/13/26 2:58 PM, Hongling Zeng wrote:
> > > > When kobject_init_and_add() fails in sysfs_slab_add(), the kobject
> > > > is not properly cleaned up, causing a memory leak.
> > > >
> > > > According to the kobject API documentation, when kobject_init_and_add()
> > > > returns an error, the caller must call kobject_put() to properly clean
> > > > up the memory associated with the object. The current code only frees
> > > > the 'name' string but forgets to release the kobject reference.
> > > This was intentional, please see commit 2420baa8e046 ("mm/slab: Allow
> > > cache creation to proceed even if sysfs registration fails").
> >    Thank you for the clarification. I see now that this was an intentional
> >    design choice to allow cache creation to proceed even when sysfs
> >    registration fails.
> >
> > > > Fix this by calling kobject_put() before jumping to the error label.
> > > >
> > > > Fixes: 54b6a731025f ("slub: fix leak of 'name' in sysfs_slab_add")
> > > > Signed-off-by: Hongling Zeng <zenghongling@xxxxxxxxxx>
> > > > ---
> > > Uh, there was a similar attempt recently...
> > >
> > > https://lore.kernel.org/linux-mm/
> > > gimwkjjpvwu2sg5625b3eeatw2vhv7rs6enm3vepdduhcefbf5@xen5iec7sn3z
> > >
> > > Sounds like we need a comment saying it is intentional!
> >   Good idea. Would a patch adding a comment like this be useful?
> >
> >            err = kobject_init_and_add(&s->kobj, &slab_ktype, NULL, "%s",
> > name);
> >    +       /*
> >    +        * Note: Intentionally not calling kobject_put() on error.
> >    +        *
> >    +        * The kobject release callback (slab_kmem_cache_release) would
> >    +        * free the entire kmem_cache structure. However, sysfs
> >    +        * registration failures are treated as non-fatal - the cache
> >    +        * continues to be used. See commit 2420baa8e046 ("mm/slab: Allow
> >    +        * cache creation to proceed even if sysfs registration fails").
> >    +        */
> Could we make it bit more concise please?
>
> Something like
>
> "Intentionally skip kobject_put(). See commit 2420baa8e046 ("mm/slab:
> Allow cache creation to proceed even if sysfs registration fails")"
>
> >            if (err)
> >                    goto out;
> >   
  Thank you for the suggestion. Here's the simplified version:

  [PATCH v1] mm/slub: add comment explaining intentional kobject handling
  in sysfs_slab_add

  Please review.

  Thanks!

  Best regards,
  Hongling Zeng