From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH net] net: phy: sfp: Prevent NULL deference of socket_ops Date: Sat, 15 Sep 2018 08:32:28 +0100 Message-ID: <20180915073228.GE30658@n2100.armlinux.org.uk> References: <20180914230132.23228-1-f.fainelli@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, Andrew Lunn , "David S. Miller" , open list To: Florian Fainelli Return-path: Content-Disposition: inline In-Reply-To: <20180914230132.23228-1-f.fainelli@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Sep 14, 2018 at 04:01:31PM -0700, Florian Fainelli wrote: > In case we have specified a SFP and an I2C phandle in the Device Tree, > but we somehow failed to look up the I2C adapter (e.g: the driver is not > enabled), we will leave dangling socket_ops, and the sfp_bus will still > have been registered. We can then observe NULL pointer dereferences > while doing ethtool -m: > > [ 20.218613] Unable to handle kernel NULL pointer dereference at virtual address 00000008 > [ 20.226977] pgd = (ptrval) > [ 20.229785] [00000008] *pgd=7c400831, *pte=00000000, *ppte=00000000 > [ 20.236274] Internal error: Oops: 17 [#1] SMP ARM > [ 20.241122] Modules linked in: > [ 20.244278] CPU: 0 PID: 1480 Comm: ethtool Not tainted 4.19.0-rc3 #138 > [ 20.251013] Hardware name: Broadcom Northstar Plus SoC > [ 20.256316] PC is at sfp_get_module_info+0x8/0x10 > [ 20.261172] LR is at dev_ethtool+0x218c/0x2afc > > Specifically guard against that. The other alternative to this would be to only set ndev->sfp_bus when the bus moves to registered state, which would probably be a saner alternative than to add an additional layer of tests. IOW: drivers/net/phy/sfp-bus.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/phy/sfp-bus.c b/drivers/net/phy/sfp-bus.c index 48ca980f5c96..c4c2b5269216 100644 --- a/drivers/net/phy/sfp-bus.c +++ b/drivers/net/phy/sfp-bus.c @@ -362,6 +362,7 @@ static int sfp_register_bus(struct sfp_bus *bus) } if (bus->started) bus->socket_ops->start(bus->sfp); + bus->netdev->sfp_bus = bus; bus->registered = true; return 0; } @@ -370,6 +371,7 @@ static void sfp_unregister_bus(struct sfp_bus *bus) { const struct sfp_upstream_ops *ops = bus->upstream_ops; + bus->netdev->sfp_bus = NULL; if (bus->registered) { if (bus->started) bus->socket_ops->stop(bus->sfp); @@ -451,7 +453,6 @@ static void sfp_upstream_clear(struct sfp_bus *bus) { bus->upstream_ops = NULL; bus->upstream = NULL; - bus->netdev->sfp_bus = NULL; bus->netdev = NULL; } @@ -480,7 +481,6 @@ struct sfp_bus *sfp_register_upstream(struct fwnode_handle *fwnode, bus->upstream_ops = ops; bus->upstream = upstream; bus->netdev = ndev; - ndev->sfp_bus = bus; if (bus->sfp) { ret = sfp_register_bus(bus); -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 13.8Mbps down 630kbps up According to speedtest.net: 13Mbps down 490kbps up