Re: [PATCH v6] IB/mlx4: Fix refcount leak in add_port() error path

[Guangshuo Li]

Hi Leon,

Thanks for reviewing.

On Sun, 17 May 2026 at 22:27, Leon Romanovsky <leon@xxxxxxxxxx> wrote:
>
> On Thu, May 14, 2026 at 07:01:39PM +0800, Guangshuo Li wrote:
> > After kobject_init_and_add(), the lifetime of the embedded struct
> > kobject is expected to be managed through the kobject core reference
> > counting.
> >
> > In add_port(), several failure paths after kobject_init_and_add() free
> > struct mlx4_port directly instead of releasing the embedded kobject with
> > kobject_put(). This leaves the kobject reference count unbalanced and can
> > lead to incorrect lifetime handling.
> >
> > Allocate the pkey and gid attribute arrays before kobject_init_and_add(),
> > so failures before kobject initialization can be handled by directly
> > freeing the allocated memory. Once kobject_init_and_add() has been
> > called, route failures through kobject_put(), and call kobject_del()
> > before kobject_put() on later failure paths after the kobject has been
> > successfully added.
> >
> > Fixes: c1e7e466120b ("IB/mlx4: Add iov directory in sysfs under the ib device")
> > Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
> > ---
> > v6:
> >   - drop the Cc stable tag
> >   - allocate pkey and gid attribute arrays before kobject_init_and_add()
> >   - keep the release callback unchanged by ensuring the attribute arrays
> >     are initialized before kobject_init_and_add()
> >
> > v5:
> >   - split the add_port() error paths after kobject_init_and_add()
> >   - call kobject_del() before kobject_put() for failures after
> >     kobject_init_and_add() succeeds
> >
> > v4:
> >   - route all add_port() failures after kobject_init_and_add() through
> >     a single kobject_put() based error path
> >   - remove duplicated attribute array frees from add_port()
> >   - keep mlx4_port_release() tolerant of partially initialized objects
> >
> > v3:
> >   - make mlx4_port_release() tolerate NULL attribute arrays
> >   - drop the parent kobject reference on the kobject_init_and_add()
> >     failure path before putting the embedded kobject
> >
> > v2:
> >   - note that the issue was identified by my static analysis tool
> >   - and confirmed by manual review
> >
> >  drivers/infiniband/hw/mlx4/sysfs.c | 39 ++++++++++++++++--------------
> >  1 file changed, 21 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/infiniband/hw/mlx4/sysfs.c b/drivers/infiniband/hw/mlx4/sysfs.c
> > index b8fa4ecfc961..e4c822c96ee6 100644
> > --- a/drivers/infiniband/hw/mlx4/sysfs.c
> > +++ b/drivers/infiniband/hw/mlx4/sysfs.c
> > @@ -636,12 +636,6 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
> >       p->port_num = port_num;
> >       p->slave = slave;
> >
> > -     ret = kobject_init_and_add(&p->kobj, &port_type,
> > -                                kobject_get(dev->dev_ports_parent[slave]),
> > -                                "%d", port_num);
> > -     if (ret)
> > -             goto err_alloc;
> > -
> >       p->pkey_group.name  = "pkey_idx";
> >       p->pkey_group.attrs =
> >               alloc_group_attrs(show_port_pkey,
> > @@ -649,13 +643,9 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
> >                                 dev->dev->caps.pkey_table_len[port_num]);
> >       if (!p->pkey_group.attrs) {
> >               ret = -ENOMEM;
> > -             goto err_alloc;
> > +             goto err_free_port;
> >       }
> >
> > -     ret = sysfs_create_group(&p->kobj, &p->pkey_group);
> > -     if (ret)
> > -             goto err_free_pkey;
> > -
> >       p->gid_group.name  = "gid_idx";
> >       p->gid_group.attrs = alloc_group_attrs(show_port_gid_idx, NULL, 1);
> >       if (!p->gid_group.attrs) {
> > @@ -663,28 +653,41 @@ static int add_port(struct mlx4_ib_dev *dev, int port_num, int slave)
> >               goto err_free_pkey;
> >       }
> >
> > +     ret = kobject_init_and_add(&p->kobj, &port_type,
> > +                                kobject_get(dev->dev_ports_parent[slave]),
> > +                                "%d", port_num);
> > +     if (ret)
> > +             goto err_put;
> > +
> > +     ret = sysfs_create_group(&p->kobj, &p->pkey_group);
> > +     if (ret)
> > +             goto err_del;
> > +
> >       ret = sysfs_create_group(&p->kobj, &p->gid_group);
> >       if (ret)
> > -             goto err_free_gid;
> > +             goto err_del;
>
> You should call to sysfs_remove_group() too.
>
> Thanks
>
I added sysfs_remove_group() for the successfully created
pkey/gid groups before kobject_del() and sent v7.