From: Abhishek Sahu abhsahu@nvidia.com
[ Upstream commit eadf88ecf6ac7d6a9f47a76c6055d9a1987a8991 ]
If 'vfio_pci_core_device::needs_pm_restore' is set (PCI device does not have No_Soft_Reset bit set in its PMCSR config register), then the current PCI state will be saved locally in 'vfio_pci_core_device::pm_save' during D0->D3hot transition and same will be restored back during D3hot->D0 transition. For saving the PCI state locally, pci_store_saved_state() is being used and the pci_load_and_free_saved_state() will free the allocated memory.
But for reset related IOCTLs, vfio driver calls PCI reset-related API's which will internally change the PCI power state back to D0. So, when the guest resumes, then it will get the current state as D0 and it will skip the call to vfio_pci_set_power_state() for changing the power state to D0 explicitly. In this case, the memory pointed by 'pm_save' will never be freed. In a malicious sequence, the state changing to D3hot followed by VFIO_DEVICE_RESET/VFIO_DEVICE_PCI_HOT_RESET can be run in a loop and it can cause an OOM situation.
This patch frees the earlier allocated memory first before overwriting 'pm_save' to prevent the mentioned memory leak.
Fixes: 51ef3a004b1e ("vfio/pci: Restore device state on PM transition") Signed-off-by: Abhishek Sahu abhsahu@nvidia.com Link: https://lore.kernel.org/r/20220217122107.22434-2-abhsahu@nvidia.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/pci/vfio_pci_core.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index a03b5a99c2da..0c63091cc848 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -228,6 +228,19 @@ int vfio_pci_set_power_state(struct vfio_pci_core_device *vdev, pci_power_t stat if (!ret) { /* D3 might be unsupported via quirk, skip unless in D3 */ if (needs_save && pdev->current_state >= PCI_D3hot) { + /* + * The current PCI state will be saved locally in + * 'pm_save' during the D3hot transition. When the + * device state is changed to D0 again with the current + * function, then pci_store_saved_state() will restore + * the state and will free the memory pointed by + * 'pm_save'. There are few cases where the PCI power + * state can be changed to D0 without the involvement + * of the driver. For these cases, free the earlier + * allocated memory first before overwriting 'pm_save' + * to prevent the memory leak. + */ + kfree(vdev->pm_save); vdev->pm_save = pci_store_saved_state(pdev); } else if (needs_restore) { pci_load_and_free_saved_state(pdev, &vdev->pm_save);