In the Linux kernel, the following vulnerability has been resolved: iommu/tegra241-cmdqv: Fix warnings due to dmam_free_coherent() Two WARNINGs are observed when SMMU driver rolls back upon failure: arm-smmu-v3.9.auto: Failed to register iommu arm-smmu-v3.9.auto: probe with driver arm-smmu-v3 failed with error -22 ------------[ cut here ]------------ WARNING: CPU: 5 PID: 1 at kernel/dma/mapping.c:74 dmam_free_coherent+0xc0/0xd8 Call trace: dmam_free_coherent+0xc0/0xd8 (P) tegra241_vintf_free_lvcmdq+0x74/0x188 tegra241_cmdqv_remove_vintf+0x60/0x148 tegra241_cmdqv_remove+0x48/0xc8 arm_smmu_impl_remove+0x28/0x60 devm_action_release+0x1c/0x40 ------------[ cut here ]------------ 128 pages are still in use! WARNING: CPU: 16 PID: 1 at mm/page_alloc.c:6902 free_contig_range+0x18c/0x1c8 Call trace: free_contig_range+0x18c/0x1c8 (P) cma_release+0x154/0x2f0 dma_free_contiguous+0x38/0xa0 dma_direct_free+0x10c/0x248 dma_free_attrs+0x100/0x290 dmam_free_coherent+0x78/0xd8 tegra241_vintf_free_lvcmdq+0x74/0x160 tegra241_cmdqv_remove+0x98/0x198 arm_smmu_impl_remove+0x28/0x60 devm_action_release+0x1c/0x40 This is because the LVCMDQ queue memory are managed by devres, while that dmam_free_coherent() is called in the context of devm_action_release(). Jason pointed out that "arm_smmu_impl_probe() has mis-ordered the devres callbacks if ops->device_remove() is going to be manually freeing things that probe allocated": https://lore.kernel.org/linux-iommu/20250407174408.GB1722458@nvidia.com/ In fact, tegra241_cmdqv_init_structures() only allocates memory resources which means any failure that it generates would be similar to -ENOMEM, so there is no point in having that "falling back to standard SMMU" routine, as the standard SMMU would likely fail to allocate memory too. Remove the unwind part in tegra241_cmdqv_init_structures(), and return a proper error code to ask SMMU driver to call tegra241_cmdqv_remove() via impl_ops->device_remove(). Then, drop tegra241_vintf_free_lvcmdq() since devres will take care of that.
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