In some cases, one device may not associated with any iommu_group.
For example, not enough DMA address space.

For those devices, kernel will crash when try to remove it from an iommu_group.

This patch do the check before remove it.

Signed-off-by: Wei Yang <redacted>
---
 drivers/iommu/iommu.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index fbe9ca7..fe41946 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c

@@ -379,6 +379,9 @@ void iommu_group_remove_device(struct device *dev)
 	struct iommu_group *group = dev->iommu_group;
 	struct iommu_device *tmp_device, *device = NULL;
 
+	if (!group)
+		return;
+
 	/* Pre-notify listeners that a device is being removed. */
 	blocking_notifier_call_chain(&group->notifier,
 				     IOMMU_GROUP_NOTIFY_DEL_DEVICE, dev);

-- 
1.7.5.4