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vfio-pci: Don't use device_lock around AER interrupt setup 

device_lock is much too prone to lockups.  For instance if we have a
pending .remove then device_lock is already held.  If userspace
attempts to modify AER signaling after that point, a deadlock occurs.
eventfd setup/teardown is already protected in vfio with the igate
mutex.  AER is not a high performance interrupt, so we can also use
the same mutex to protect signaling versus setup races.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Alex Williamson 2014-01-14 16:12:55 -07:00
parent d10999016f
commit 3be3a074cf
2 changed files with 4 additions and 17 deletions
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4
drivers/vfio/pci/vfio_pci.c
View File

@ -883,9 +883,13 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
return PCI_ERS_RESULT_DISCONNECT;
}
mutex_lock(&vdev->igate);
if (vdev->err_trigger)
eventfd_signal(vdev->err_trigger, 1);
mutex_unlock(&vdev->igate);
vfio_device_put(device);
return PCI_ERS_RESULT_CAN_RECOVER;

17
drivers/vfio/pci/vfio_pci_intrs.c
View File

@ -749,54 +749,37 @@ static int vfio_pci_set_err_trigger(struct vfio_pci_device *vdev,
unsigned count, uint32_t flags, void *data)
{
int32_t fd = *(int32_t *)data;
struct pci_dev *pdev = vdev->pdev;
if ((index != VFIO_PCI_ERR_IRQ_INDEX) ||
!(flags & VFIO_IRQ_SET_DATA_TYPE_MASK))
return -EINVAL;
/*
* device_lock synchronizes setting and checking of
* err_trigger. The vfio_pci_aer_err_detected() is also
* called with device_lock held.
*/
/* DATA_NONE/DATA_BOOL enables loopback testing */
if (flags & VFIO_IRQ_SET_DATA_NONE) {
device_lock(&pdev->dev);
if (vdev->err_trigger)
eventfd_signal(vdev->err_trigger, 1);
device_unlock(&pdev->dev);
return 0;
} else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
uint8_t trigger = *(uint8_t *)data;
device_lock(&pdev->dev);
if (trigger && vdev->err_trigger)
eventfd_signal(vdev->err_trigger, 1);
device_unlock(&pdev->dev);
return 0;
}
/* Handle SET_DATA_EVENTFD */
if (fd == -1) {
device_lock(&pdev->dev);
if (vdev->err_trigger)
eventfd_ctx_put(vdev->err_trigger);
vdev->err_trigger = NULL;
device_unlock(&pdev->dev);
return 0;
} else if (fd >= 0) {
struct eventfd_ctx *efdctx;
efdctx = eventfd_ctx_fdget(fd);
if (IS_ERR(efdctx))
return PTR_ERR(efdctx);
device_lock(&pdev->dev);
if (vdev->err_trigger)
eventfd_ctx_put(vdev->err_trigger);
vdev->err_trigger = efdctx;
device_unlock(&pdev->dev);
return 0;
} else
return -EINVAL;