Re: [PATCH net 2/2] fsl/fman: Fix refcount handling of fman-related devices

[Aleksandr Mishin]

On 17.10.2024 13:01, Paolo Abeni wrote:
> On 10/15/24 08:01, Aleksandr Mishin wrote:
> > In mac_probe() there are multiple calls to of_find_device_by_node(),
> > fman_bind() and fman_port_bind() which takes references to of_dev->dev.
> > Not all references taken by these calls are released later on error path
> > in mac_probe() and in mac_remove() which lead to reference leaks.
> >
> > Add references release.
> >
> > Fixes: 3933961682a3 ("fsl/fman: Add FMan MAC driver")
> > Signed-off-by: Aleksandr Mishin <amishin@xxxxxxxxxx>
> > ---
> > Compile tested only.
> >
> >   drivers/net/ethernet/freescale/fman/mac.c | 62 +++++++++++++++++------
> >   1 file changed, 47 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/fman/mac.c 
> > b/drivers/net/ethernet/freescale/fman/mac.c
> > index 9b863db0bf08..11da139082e1 100644
> > --- a/drivers/net/ethernet/freescale/fman/mac.c
> > +++ b/drivers/net/ethernet/freescale/fman/mac.c
> > @@ -204,7 +204,7 @@ static int mac_probe(struct platform_device 
> > *_of_dev)
> >       if (err) {
> >           dev_err(dev, "failed to read cell-index for %pOF\n", 
> > dev_node);
> >           err = -EINVAL;
> > -        goto _return_of_node_put;
> > +        goto _return_dev_put;
>
> We are after a succesful of_find_device_by_node and prior to 
> fman_bind(), mac_dev->fman_dev refcount is 1


Indeed. refcounts = 1.


> > @@ -213,40 +213,51 @@ static int mac_probe(struct platform_device 
> > *_of_dev)
> >       if (!priv->fman) {
> >           dev_err(dev, "fman_bind(%pOF) failed\n", dev_node);
> >           err = -ENODEV;
> > -        goto _return_of_node_put;
> > +        goto _return_dev_put;
> >       }


refcounts: 1 + 1 = 2.


> >   +    /* Two references have been taken in of_find_device_by_node()
> > +     * and fman_bind(). Release one of them here. The second one
> > +     * will be released in mac_remove().
> > +     */
> > +    put_device(mac_dev->fman_dev);


refcounts: 2 - 1 = 1.


> >       of_node_put(dev_node);
> > +    dev_node = NULL;
> >         /* Get the address of the memory mapped registers */
> >       mac_dev->res = platform_get_mem_or_io(_of_dev, 0);
> >       if (!mac_dev->res) {
> >           dev_err(dev, "could not get registers\n");
> > -        return -EINVAL;
> > +        err = -EINVAL;
> > +        goto _return_dev_put;
>
> Here we are after a successful fman_bind(), mac_dev->fman_dev refcount 
> is 2. _return_dev_put will drop a single reference, this error path 
> looks buggy.


We released 1 reference above with "put_device(mac_dev->fman_dev);".


> Similar issue for the _return_dev_arr_put error path below.


Similar situation: we release 1 reference with 
"put_device(mac_dev->fman_port_devs[i]);".


> Cheers,
>
> Paolo
--
Kind regards
Aleksandr