On Tue, Nov 01, 2016 at 12:48:48PM -0400, David Miller wrote: > From: Johan Hovold <jo...@kernel.org> > Date: Tue, 1 Nov 2016 17:42:25 +0100 > > > On Tue, Nov 01, 2016 at 12:27:11PM -0400, David Miller wrote: > >> From: Johan Hovold <jo...@kernel.org> > >> Date: Tue, 1 Nov 2016 12:03:35 +0100 > >> > >> > diff --git a/drivers/net/ethernet/ti/cpsw-phy-sel.c > >> > b/drivers/net/ethernet/ti/cpsw-phy-sel.c > >> > index 054a8dd23dae..589beb843f56 100644 > >> > --- a/drivers/net/ethernet/ti/cpsw-phy-sel.c > >> > +++ b/drivers/net/ethernet/ti/cpsw-phy-sel.c > >> > @@ -176,8 +176,11 @@ void cpsw_phy_sel(struct device *dev, > >> > phy_interface_t phy_mode, int slave) > >> > } > >> > > >> > dev = bus_find_device(&platform_bus_type, NULL, node, match); > >> > + of_node_put(node); > >> > priv = dev_get_drvdata(dev); > >> > > >> > + put_device(dev); > >> > + > >> > priv->cpsw_phy_sel(priv, phy_mode, slave); > >> > } > >> > EXPORT_SYMBOL_GPL(cpsw_phy_sel); > >> > >> The only reference you have to 'dev' is the one obtained from the > >> bus_find_device() call, therefore you must at least hold onto > >> 'dev' until after the priv->cpsw_phy_sel(priv, phy_mode, slave); call. > > > > As I mentioned in the commit message "...there is no guarantee that the > > devres-managed struct cpsw_phy_sel_priv will continue to be valid until > > this function returns regardless of this change". > > > > Specifically, holding a reference to dev does not prevent the > > cpsw_phy_sel driver from being unbound and priv from being freed. > > But you should at least hold onto the object while you call a function > pointer embedded in a data structure referred by it.
But there is no such reference to be held (currently). While priv is valid (i.e. dev has a driver bound), driver core will hold a reference to dev. If someone unbinds the driver, priv will be gone long before dev and all bets are off anyway. So I released the reference to dev before dereferencing priv on purpose to avoid having someone make false assumptions about the lifetime of priv. Johan
