iommu: Check if group is NULL before remove device

If probe_device is failing, iommu_group is not initialized because
iommu_group_add_device is not reached, so freeing it will result
in NULL pointer access.

iommu_bus_init
  ->bus_iommu_probe
      ->probe_iommu_group in for each:/* return -22 in fail case */
          ->iommu_probe_device
              ->__iommu_probe_device       /* return -22 here.*/
                  -> ops->probe_device          /* return -22 here.*/
                  -> iommu_group_get_for_dev
                        -> ops->device_group
                        -> iommu_group_add_device //good case
  ->remove_iommu_group  //in fail case, it will remove group
     ->iommu_release_device
         ->iommu_group_remove_device // here we don't have group

In my case ops->probe_device (mtk_iommu_probe_device from
mtk_iommu_v1.c) is due to failing fwspec->ops mismatch.

Fixes: d72e31c93746 ("iommu: IOMMU Groups")
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Link: https://lore.kernel.org/r/20210731074737.4573-1-linux@fw-web.de
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 5419c4b..63f0af1 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -924,6 +924,9 @@ void iommu_group_remove_device(struct device *dev)
        struct iommu_group *group = dev->iommu_group;
        struct group_device *tmp_device, *device = NULL;
 
+       if (!group)
+               return;
+
        dev_info(dev, "Removing from iommu group %d\n", group->id);
 
        /* Pre-notify listeners that a device is being removed. */