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SubjectRe: [PATCH v3 09/14] iommu/arm-smmu: Prevent forced unbinding of Arm SMMU drivers
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On 21/11/2019 11:49, Will Deacon wrote:
> Forcefully unbinding the Arm SMMU drivers is a pretty dangerous operation,
> since it will likely lead to catastrophic failure for any DMA devices
> mastering through the SMMU being unbound. When the driver then attempts
> to "handle" the fatal faults, it's very easy to trip over dead data
> structures, leading to use-after-free.
>
> On John's machine, he reports that the machine was "unusable" due to
> loss of the storage controller following a forced unbind of the SMMUv3
> driver:
>
> | # cd ./bus/platform/drivers/arm-smmu-v3
> | # echo arm-smmu-v3.0.auto > unbind
> | hisi_sas_v2_hw HISI0162:01: CQE_AXI_W_ERR (0x800) found!
> | platform arm-smmu-v3.0.auto: CMD_SYNC timeout at 0x00000146
> | [hwprod 0x00000146, hwcons 0x00000000]
>
> Prevent this forced unbinding of the drivers by setting "suppress_bind_attrs"
> to true.

This seems a reasonable approach for now.

BTW, I'll give this series a spin this week, which again looks to be
your iommu/module branch, excluding the new IORT patch.

Cheers,
John

>
> Link: https://lore.kernel.org/lkml/06dfd385-1af0-3106-4cc5-6a5b8e864759@huawei.com
> Reported-by: John Garry <john.garry@huawei.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
> drivers/iommu/arm-smmu-v3.c | 5 +++--
> drivers/iommu/arm-smmu.c | 7 ++++---
> 2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 2ad8e2ca0583..3fd75abce3bb 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -3700,8 +3700,9 @@ MODULE_DEVICE_TABLE(of, arm_smmu_of_match);
>
> static struct platform_driver arm_smmu_driver = {
> .driver = {
> - .name = "arm-smmu-v3",
> - .of_match_table = of_match_ptr(arm_smmu_of_match),
> + .name = "arm-smmu-v3",
> + .of_match_table = of_match_ptr(arm_smmu_of_match),
> + .suppress_bind_attrs = true,
> },
> .probe = arm_smmu_device_probe,
> .remove = arm_smmu_device_remove,
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 53bbe0663b9e..d6c83bd69555 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -2237,9 +2237,10 @@ static const struct dev_pm_ops arm_smmu_pm_ops = {
>
> static struct platform_driver arm_smmu_driver = {
> .driver = {
> - .name = "arm-smmu",
> - .of_match_table = of_match_ptr(arm_smmu_of_match),
> - .pm = &arm_smmu_pm_ops,
> + .name = "arm-smmu",
> + .of_match_table = of_match_ptr(arm_smmu_of_match),
> + .pm = &arm_smmu_pm_ops,
> + .suppress_bind_attrs = true,
> },
> .probe = arm_smmu_device_probe,
> .remove = arm_smmu_device_remove,
>

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