linux/drivers/vfio
Alex Williamson 4bc94d5dc9 vfio: Fix lockdep issue
When we open a device file descriptor, we currently have the
following:

vfio_group_get_device_fd()
  mutex_lock(&group->device_lock);
    open()
    ...
    if (ret)
      release()

If we hit that error case, we call the backend driver release path,
which for vfio-pci looks like this:

vfio_pci_release()
  vfio_pci_disable()
    vfio_pci_try_bus_reset()
      vfio_pci_get_devs()
        vfio_device_get_from_dev()
          vfio_group_get_device()
            mutex_lock(&group->device_lock);

Whoops, we've stumbled back onto group.device_lock and created a
deadlock.  There's a low likelihood of ever seeing this play out, but
obviously it needs to be fixed.  To do that we can use a reference to
the vfio_device for vfio_group_get_device_fd() rather than holding the
lock.  There was a loop in this function, theoretically allowing
multiple devices with the same name, but in practice we don't expect
such a thing to happen and the code is already aborting from the loop
with break on any sort of error rather than continuing and only
parsing the first match anyway, so the loop was effectively unused
already.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Fixes: 20f300175a ("vfio/pci: Fix racy vfio_device_get_from_dev() call")
Reported-by: Joerg Roedel <joro@8bytes.org>
Tested-by: Joerg Roedel <jroedel@suse.de>
2015-07-24 15:14:04 -06:00
..
pci vfio/pci: Fix racy vfio_device_get_from_dev() call 2015-06-09 10:08:57 -06:00
platform VFIO: platform: enable ARM64 build 2015-06-22 09:35:47 -06:00
Kconfig drivers/vfio: Allow type-1 IOMMU instantiation on top of an ARM SMMUv3 2015-05-29 11:12:40 +02:00
Makefile vfio: Split virqfd into a separate module for vfio bus drivers 2015-03-17 08:33:38 -06:00
vfio_iommu_spapr_tce.c vfio: powerpc/spapr: Support Dynamic DMA windows 2015-06-11 15:16:55 +10:00
vfio_iommu_type1.c vfio/type1: Add conditional rescheduling 2015-02-06 14:19:12 -07:00
vfio_spapr_eeh.c drivers/vfio: Support EEH error injection 2015-05-12 20:33:35 +10:00
vfio.c vfio: Fix lockdep issue 2015-07-24 15:14:04 -06:00
virqfd.c vfio: Split virqfd into a separate module for vfio bus drivers 2015-03-17 08:33:38 -06:00