On Thu, Nov 20, 2025 at 05:04:13PM -0700, Alex Williamson wrote: > On Thu, 20 Nov 2025 11:28:29 +0200 > Leon Romanovsky <[email protected]> wrote: > > diff --git a/drivers/vfio/pci/vfio_pci_core.c > > b/drivers/vfio/pci/vfio_pci_core.c > > index 142b84b3f225..51a3bcc26f8b 100644 > > --- a/drivers/vfio/pci/vfio_pci_core.c > > +++ b/drivers/vfio/pci/vfio_pci_core.c > ... > > @@ -2487,8 +2500,11 @@ static int vfio_pci_dev_set_hot_reset(struct > > vfio_device_set *dev_set, > > > > err_undo: > > list_for_each_entry_from_reverse(vdev, &dev_set->device_list, > > - vdev.dev_set_list) > > + vdev.dev_set_list) { > > + if (__vfio_pci_memory_enabled(vdev)) > > + vfio_pci_dma_buf_move(vdev, false); > > up_write(&vdev->memory_lock); > > + } > > I ran into a bug here. In the hot reset path we can have dev_sets > where one or more devices are not opened by the user. The vconfig > buffer for the device is established on open. However: > > bool __vfio_pci_memory_enabled(struct vfio_pci_core_device *vdev) > { > struct pci_dev *pdev = vdev->pdev; > u16 cmd = le16_to_cpu(*(__le16 *)&vdev->vconfig[PCI_COMMAND]); > ... > > Leads to a NULL pointer dereference. > > I think the most straightforward fix is simply to test the open_count > on the vfio_device, which is also protected by the dev_set->lock that > we already hold here: > > --- a/drivers/vfio/pci/vfio_pci_core.c > +++ b/drivers/vfio/pci/vfio_pci_core.c > @@ -2501,7 +2501,7 @@ static int vfio_pci_dev_set_hot_reset(struct > vfio_device_set *dev_set, > err_undo: > list_for_each_entry_from_reverse(vdev, &dev_set->device_list, > vdev.dev_set_list) { > - if (__vfio_pci_memory_enabled(vdev)) > + if (vdev->vdev.open_count && __vfio_pci_memory_enabled(vdev)) > vfio_pci_dma_buf_move(vdev, false); > up_write(&vdev->memory_lock); > } > > Any other suggestions? This should be the only reset path with this > nuance of affecting non-opened devices. Thanks,
It seems right to me. Thanks > > Alex
