iommu/arm-smmu: Defer probe of clients after smmu device bound

commit 229e6ee43d2a160a1592b83aad620d6027084aad upstream.

Null pointer dereference occurs due to a race between smmu
driver probe and client driver probe, when of_dma_configure()
for client is called after the iommu_device_register() for smmu driver
probe has executed but before the driver_bound() for smmu driver
has been called.

Following is how the race occurs:

T1:Smmu device probe		T2: Client device probe

really_probe()
arm_smmu_device_probe()
iommu_device_register()
					really_probe()
					platform_dma_configure()
					of_dma_configure()
					of_dma_configure_id()
					of_iommu_configure()
					iommu_probe_device()
					iommu_init_device()
					arm_smmu_probe_device()
					arm_smmu_get_by_fwnode()
						driver_find_device_by_fwnode()
						driver_find_device()
						next_device()
						klist_next()
						    /* null ptr
						       assigned to smmu */
					/* null ptr dereference
					   while smmu->streamid_mask */
driver_bound()
	klist_add_tail()

When this null smmu pointer is dereferenced later in
arm_smmu_probe_device, the device crashes.

Fix this by deferring the probe of the client device
until the smmu device has bound to the arm smmu driver.

Fixes: 021bb8420d44 ("iommu/arm-smmu: Wire up generic configuration support")
Cc: stable@vger.kernel.org
Co-developed-by: Prakash Gupta <quic_guptap@quicinc.com>
Signed-off-by: Prakash Gupta <quic_guptap@quicinc.com>
Signed-off-by: Pratyush Brahma <quic_pbrahma@quicinc.com>
Link: https://lore.kernel.org/r/20241004090428.2035-1-quic_pbrahma@quicinc.com
[will: Add comment]
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 8321962b37148bae0db9aa161cb96395ed740320..14618772a3d6e47ceab3f8666dc11271157f8f74 100644 (file)
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1437,6 +1437,17 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
                        goto out_free;
        } else {
                smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode);
+
+               /*
+                * Defer probe if the relevant SMMU instance hasn't finished
+                * probing yet. This is a fragile hack and we'd ideally
+                * avoid this race in the core code. Until that's ironed
+                * out, however, this is the most pragmatic option on the
+                * table.
+                */
+               if (!smmu)
+                       return ERR_PTR(dev_err_probe(dev, -EPROBE_DEFER,
+                                               "smmu dev has not bound yet\n"));
        }
 
        ret = -EINVAL;