linux-kernel - Re: [PATCH] pci: iov: use device lock to protect IOV sysfs accesses

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Message-ID: <20170526165820.7ec488e3@cakuba.netronome.com>
Date:   Fri, 26 May 2017 16:58:20 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Emil Tantilov <emil.s.tantilov@...el.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH] pci: iov: use device lock to protect IOV sysfs accesses

On Fri, 26 May 2017 18:47:26 -0500, Bjorn Helgaas wrote:
> On Mon, May 22, 2017 at 03:50:23PM -0700, Jakub Kicinski wrote:
> > PCI core sets the driver pointer before calling ->probe() and only
> > clears it after ->remove().  This means driver's ->sriov_configure()
> > callback will happily race with probe() and remove(), most likely
> > leading to BUGs, since drivers don't expect this.  
> 
> I guess you're referring to the pci_dev->driver pointer set by
> local_pci_probe(), and this is important because sriov_numvfs_store()
> checks that pointer, right?

Yes, exactly.  I initially thought this is how the safety of sriov
callback may have been ensured, but since the order of
local_pci_probe() and the assignment is what it is, it can't.