[PATCH 4/5] iommu/vt-d: Tear down scalable-mode context on probe failure

[Lu Baolu]

intel_pasid_setup_sm_context() walks a PCI device’s DMA aliases via
pci_for_each_dma_alias() and programs a scalable-mode context entry for
each RID. For a device with a dma_alias_mask, the callback is invoked
once for the device’s own RID and once for each alias bit, all with the
same pci_dev, so device_pasid_table_setup() runs for multiple RIDs.

pci_for_each_dma_alias() stops at the first callback error. Therefore, a
failure partway through the walk can leave context entries for already
processed RIDs present and still pointing to the device’s PASID table.

On this error path, intel_iommu_probe_device() currently jumps directly
to intel_pasid_free_table(), which frees the PASID table without
first tearing down those context entries. The IOMMU may then walk a
present context entry whose PASID table pointer references freed
memory.

intel_iommu_release_device() already performs teardown before freeing the
table. Apply the same ordering on the probe failure path.

device_pasid_table_teardown() safely handles RIDs that were never
programmed: iommu_context_addr() returns NULL when no context table has
been allocated, and clearing the Present bit of an already non-present
entry is a no-op. So unwind is safe for both the alias that failed and
any aliases not yet reached.

Fixes: 301f1a80487fd ("iommu/vt-d: Setup scalable mode context entry in probe path")
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/patchset/20260602233426.357499-1-baolu.lu%40linux.intel.com
Assisted-by: Claude:claude-opus-5
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/intel/iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 6baf1c075dc9..489e9ab5f698 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3342,6 +3342,7 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev)
 
 	return &iommu->iommu;
 free_table:
+	intel_pasid_teardown_sm_context(dev);
 	intel_pasid_free_table(dev);
 clear_rbtree:
 	device_rbtree_remove(info);
-- 
2.43.0