"value":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/arm-smmu: Defer probe of clients after smmu device bound\n\nNull pointer dereference occurs due to a race between smmu\ndriver probe and client driver probe, when of_dma_configure()\nfor client is called after the iommu_device_register() for smmu driver\nprobe has executed but before the driver_bound() for smmu driver\nhas been called.\n\nFollowing is how the race occurs:\n\nT1:Smmu device probe\t\tT2: Client device probe\n\nreally_probe()\narm_smmu_device_probe()\niommu_device_register()\n\t\t\t\t\treally_probe()\n\t\t\t\t\tplatform_dma_configure()\n\t\t\t\t\tof_dma_configure()\n\t\t\t\t\tof_dma_configure_id()\n\t\t\t\t\tof_iommu_configure()\n\t\t\t\t\tiommu_probe_device()\n\t\t\t\t\tiommu_init_device()\n\t\t\t\t\tarm_smmu_probe_device()\n\t\t\t\t\tarm_smmu_get_by_fwnode()\n\t\t\t\t\t\tdriver_find_device_by_fwnode()\n\t\t\t\t\t\tdriver_find_device()\n\t\t\t\t\t\tnext_device()\n\t\t\t\t\t\tklist_next()\n\t\t\t\t\t\t /* null ptr\n\t\t\t\t\t\t assigned to smmu */\n\t\t\t\t\t/* null ptr dereference\n\t\t\t\t\t while smmu->streamid_mask */\ndriver_bound()\n\tklist_add_tail()\n\nWhen this null smmu pointer is dereferenced later in\narm_smmu_probe_device, the device crashes.\n\nFix this by deferring the probe of the client device\nuntil the smmu device has bound to the arm smmu driver.\n\n[will: Add comment]"
