In the Linux kernel, the following vulnerability has been resolved:
iommu/tegra241-cmdqv: Fix CMD_SYNC use-after-free on teardown
arm_smmu_impl_remove() is registered as a devres action in arm_smmu_impl_probe(), before arm_smmu_init_queues() allocates smmu->cmdq.q.base. On a devres unwind, whether a failed probe or an unbind, the queue is freed first and arm_smmu_impl_remove() then runs tegra241_cmdqv_remove_vintf(), whose VINTF deinit issues a CMD_SYNC on the freed memory.
Observed during testing with a QEMU hack that makes the VCMDQ fail to enable, so the impl reset fails and probe aborts into the devres unwind:
platform NVDA200C:00: tegra241_cmdqv: VINTF0: VCMDQ0/LVCMDQ0: failed to enable, STATUS=0x00000000 platform NVDA200C:00: tegra241_cmdqv: VINTF0: VCMDQ0/LVCMDQ0: GERRORN=0x0, GERROR=0x4, CONS=0x0 platform NVDA200C:00: tegra241_cmdqv: VINTF0: VCMDQ0/LVCMDQ0: uncleared error detected, resetting arm-smmu-v3 arm-smmu-v3.0.auto: failed to reset impl arm-smmu-v3 arm-smmu-v3.0.auto: probe with driver arm-smmu-v3 failed with error -110 Unable to handle kernel paging request at virtual address ffff8000891e0098 ... Internal error: Oops: 0000000096000047 [#1] SMP ... Call trace: arm_smmu_cmdq_issue_cmdlist+0x320/0x6fc (P) tegra241_vcmdq_hw_deinit+0x98/0x168 tegra241_vintf_hw_deinit+0x5c/0x1b0 tegra241_cmdqv_remove_vintf+0x34/0xec tegra241_cmdqv_remove+0x40/0x9c arm_smmu_impl_remove+0x20/0x30 devm_action_release+0x14/0x20 devres_release_all+0xa8/0x110 device_unbind_cleanup+0x18/0x84 really_probe+0x1f0/0x29c
Drop the VINTF deinit from tegra241_cmdqv_remove_vintf() so the unwind no longer touches the freed queue. Quiesce the VINTFs earlier instead. Add a device_disable() impl op and run it from arm_smmu_disable_action() while the CMDQ is still up. That handles a live unbind. A failed reset is already handled because tegra241_vintf_hw_init() deinits the VINTF on its own error path. tegra241_cmdqv_remove_vintf() is also used by the iommufd viommu destroy path, so quiesce there too.
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