On 2022-02-09 14:09, Aleksandr Fedorov wrote:
iommu_dma_get_resv_regions() assumes that iommu_fwspec field for
corresponding device is set which is not always true. Since
iommu_dma_get_resv_regions() seems to be a future-proof generic API
that can be used by any iommu driver, add an explicit check for NULL.
Except it's not a "generic" interface for drivers to call at random,
it's a helper for retrieving common firmware-based information
specifically for drivers already using the fwspec mechanism for common
firmware bindings. If any driver calls this with a device *without* a
valid fwnode, it deserves to crash because it's done something
fundamentally wrong.
I concur that it's not exactly obvious that "non-IOMMU-specific" means
"based on common firmware bindings, thus implying fwspec".
Robin.
Currently it can work by accident since compiler can eliminate
the 'iommu_fwspec' check altogether when CONFIG_ACPI_IORT=n, but
code elimination from optimizations is not reliable.
Signed-off-by: Aleksandr Fedorov <halc...@gmail.com>
---
A compilation failure has been observed on a gcc-compatible compiler based on
EDG.
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index d85d54f2b549..474b1b7211d7 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -382,10 +382,10 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
*/
void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list)
{
+ struct iommu_fwspec *iommu_fwspec = dev_iommu_fwspec_get(dev);
- if (!is_of_node(dev_iommu_fwspec_get(dev)->iommu_fwnode))
+ if (iommu_fwspec && !is_of_node(iommu_fwspec->iommu_fwnode))
iort_iommu_msi_get_resv_regions(dev, list);
-
}
EXPORT_SYMBOL(iommu_dma_get_resv_regions);
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