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Date: Fri, 29 Jun 2018 07:21:27 -0400
From: Neil Horman <nhorman@...driver.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: linux-rdma@...r.kernel.org, Adit Ranadive <aditr@...are.com>,
VMware PV-Drivers <pv-drivers@...are.com>,
Doug Ledford <dledford@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vmw_pvrdma: Release netdev when vmxnet3 module is removed
On Thu, Jun 28, 2018 at 02:37:09PM -0600, Jason Gunthorpe wrote:
> On Thu, Jun 28, 2018 at 03:45:26PM -0400, Neil Horman wrote:
> > On Thu, Jun 28, 2018 at 12:59:46PM -0600, Jason Gunthorpe wrote:
> > > On Thu, Jun 28, 2018 at 09:59:38AM -0400, Neil Horman wrote:
> > > > On repeated module load/unload cycles, its possible for the pvrmda
> > > > driver to encounter this crash:
> > > >
> > > > ...
> > > > 297.032448] RIP: 0010:[<ffffffff839e4620>] [<ffffffff839e4620>] netdev_walk_all_upper_dev_rcu+0x50/0xb0
> > > > [ 297.034078] RSP: 0018:ffff95087780bd08 EFLAGS: 00010286
> > > > [ 297.034986] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff95087a0c0000
> > > > [ 297.036196] RDX: ffff95087a0c0000 RSI: ffffffff839e44e0 RDI: ffff950835d0c000
> > > > [ 297.037421] RBP: ffff95087780bd40 R08: ffff95087a0e0ea0 R09: abddacd03f8e0ea0
> > > > [ 297.038636] R10: abddacd03f8e0ea0 R11: ffffef5901e9dbc0 R12: ffff95087a0c0000
> > > > [ 297.039854] R13: ffffffff839e44e0 R14: ffff95087a0c0000 R15: ffff950835d0c828
> > > > [ 297.041071] FS: 0000000000000000(0000) GS:ffff95087fc00000(0000) knlGS:0000000000000000
> > > > [ 297.042443] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > [ 297.043429] CR2: ffffffffffffffe8 CR3: 000000007a652000 CR4: 00000000003607f0
> > > > [ 297.044674] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > > [ 297.045893] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > > [ 297.047109] Call Trace:
> > > > [ 297.047545] [<ffffffff839e4698>] netdev_has_upper_dev_all_rcu+0x18/0x20
> > > > [ 297.048691] [<ffffffffc05d31af>] is_eth_port_of_netdev+0x2f/0xa0 [ib_core]
> > > > [ 297.049886] [<ffffffffc05d3180>] ? is_eth_active_slave_of_bonding_rcu+0x70/0x70 [ib_core]
> > > > ...
> > > >
> > > > This occurs because vmw_pvrdma on probe stores a pointer to the netdev
> > > > that exists on function 0 of the same bus/device/slot (which represents
> > > > the vmxnet3 ethernet driver). However, it never removes this pointer if
> > > > the vmxnet3 module is removed, leading to crashes resulting from use
> > > > after free dereferencing incidents like the one above.
> > > >
> > > > The fix is pretty straightforward. vmw_pvrdma should listen for
> > > > NETDEV_REGISTER and NETDEV_UNREGISTER events in its event listener code
> > > > block, and update the stored netdev pointer accordingly. This solution
> > > > has been tested by myself and the reporter with successful results.
> > > > This fix also allows the pvrdma driver to find its underlying ethernet
> > > > device in the event that vmxnet3 is loaded after pvrdma, which it was
> > > > not able to do before.
> > > >
> > > > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > > > Reported-by: ruquin@...hat.com
> > > > CC: Adit Ranadive <aditr@...are.com>
> > > > CC: VMware PV-Drivers <pv-drivers@...are.com>
> > > > CC: Doug Ledford <dledford@...hat.com>
> > > > CC: Jason Gunthorpe <jgg@...pe.ca>
> > > > CC: linux-kernel@...r.kernel.org
> > > > .../infiniband/hw/vmw_pvrdma/pvrdma_main.c | 25 +++++++++++++++++--
> > > > 1 file changed, 23 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/infiniband/hw/vmw_pvrdma/pvrdma_main.c b/drivers/infiniband/hw/vmw_pvrdma/pvrdma_main.c
> > > > index 0be33a81bbe6..5b4782078a74 100644
> > > > +++ b/drivers/infiniband/hw/vmw_pvrdma/pvrdma_main.c
> > > > @@ -699,8 +699,12 @@ static int pvrdma_del_gid(const struct ib_gid_attr *attr, void **context)
> > > > }
> > > >
> > > > static void pvrdma_netdevice_event_handle(struct pvrdma_dev *dev,
> > > > + struct net_device *ndev,
> > > > unsigned long event)
> > > > {
> > > > + struct pci_dev *pdev_net;
> > > > +
> > > > +
> > > > switch (event) {
> > > > case NETDEV_REBOOT:
> > > > case NETDEV_DOWN:
> > > > @@ -718,6 +722,21 @@ static void pvrdma_netdevice_event_handle(struct pvrdma_dev *dev,
> > > > else
> > > > pvrdma_dispatch_event(dev, 1, IB_EVENT_PORT_ACTIVE);
> > > > break;
> > > > + case NETDEV_UNREGISTER:
> > > > + dev_put(dev->netdev);
> > > > + dev->netdev = NULL;
> > > > + break;
> > > > + case NETDEV_REGISTER:
> > > > + /* Paired vmxnet3 will have same bus, slot. But func will be 0 */
> > > > + pdev_net = pci_get_slot(dev->pdev->bus, PCI_DEVFN(PCI_SLOT(dev->pdev->devfn), 0));
> > > > + if ((dev->netdev == NULL) && (pci_get_drvdata(pdev_net) == ndev)) {
> > > > + /* this is our netdev */
> > > > + dev->netdev = ndev;
> > > > + dev_hold(ndev);
> > > > + }
> > > > + pci_dev_put(pdev_net);
> > > > + break;
> > > > +
> > > > default:
> > > > dev_dbg(&dev->pdev->dev, "ignore netdevice event %ld on %s\n",
> > > > event, dev->ib_dev.name);
> > > > @@ -734,8 +753,9 @@ static void pvrdma_netdevice_event_work(struct work_struct *work)
> > > >
> > > > mutex_lock(&pvrdma_device_list_lock);
> > > > list_for_each_entry(dev, &pvrdma_device_list, device_link) {
> > > > - if (dev->netdev == netdev_work->event_netdev) {
> > > > - pvrdma_netdevice_event_handle(dev, netdev_work->event);
> > > > + if ((netdev_work->event == NETDEV_REGISTER) ||
> > > > + (dev->netdev == netdev_work->event_netdev)) {
> > > > + pvrdma_netdevice_event_handle(dev, netdev_work->event_netdev, netdev_work->event);
> > > > break;
> > > > }
> > > > }
> > > > @@ -962,6 +982,7 @@ static int pvrdma_pci_probe(struct pci_dev *pdev,
> > > > }
> > > >
> > > > dev->netdev = pci_get_drvdata(pdev_net);
> > > > + dev_hold(dev->netdev);
> > > > pci_dev_put(pdev_net);
> > > > if (!dev->netdev) {
> > > > dev_err(&pdev->dev, "failed to get vmxnet3 device\n");
> > >
> > > I see a lot of new dev_hold's here, where are the matching
> > > dev_puts()?
> > >
> > I'm not sure I'd call 2 alot, but sure, there is a new dev_hold in the
> > pvrdma_pci_probe routine, to hold a reference to the netdev that is looked up
> > there. It is balanced by the NETDEV_UNREGISTER case in
> > pvrdma_netdevice_event_handle. The UNREGISTER clause is also balancing the
> > NETDEV_REGISTER case of the hanlder that looks up the matching netdev should a
> > new device be registered. Note that we will only hold a single device at a
> > time, because a given pvrdma device only recongnizes a single vmxnet3 device
> > (the one on function 0 of its own bus/device tuple).
>
> I don't see how the dev_hold in pvrdma_pci_probe is undone during
> error unwind (eg goto err_free_cq_ring)
>
Ah, I missed that, thank you, I'll update the patch.
> And I don't see how it is put when pvrdma_pci_remove() is called.
>
Yup, you're right, it should be dropped there too, immediately after the
unregisteration of the netdevice notifier.
> Jason
>
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