6.6-stable review patch. If anyone has any objections, please let me know.
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From: Pratyush Brahma quic_pbrahma@quicinc.com
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 [rm: backport for context conflict prior to 6.8] Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/iommu/arm/arm-smmu/arm-smmu.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c @@ -1359,6 +1359,17 @@ static struct iommu_device *arm_smmu_pro goto out_free; } else if (fwspec && fwspec->ops == &arm_smmu_ops) { 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")); } else { return ERR_PTR(-ENODEV); }