linux-kernel - Re: [PATCH net] net: phy: sfp: Prevent NULL deference of socket

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Date:   Tue, 18 Sep 2018 00:13:46 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: phy: sfp: Prevent NULL deference of socket_ops

On Mon, Sep 17, 2018 at 10:30:52AM -0700, Florian Fainelli wrote:
> On 09/15/2018 12:32 AM, Russell King - ARM Linux wrote:
> > 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:
> 
> Indeed, your patch works for me:
> 
> Tested-by: Florian Fainelli <f.fainelli@...il.com>

Thanks, I'll re-send it properly for davem tomorrow.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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