linux-kernel - Re: [PATCH rc 2/2] iommu/tegra241-cmdqv: Fix UAF due to re-entry of tegra241_cmdqv

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Message-ID: <Z/QeqJqXJZSSPekL@nvidia.com>
Date: Mon, 7 Apr 2025 11:51:20 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <will@...nel.org>
CC: <thierry.reding@...il.com>, <vdumpa@...dia.com>, <robin.murphy@....com>,
	<joro@...tes.org>, <jonathanh@...dia.com>, <jgg@...dia.com>,
	<linux-tegra@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH rc 2/2] iommu/tegra241-cmdqv: Fix UAF due to re-entry of
 tegra241_cmdqv_remove()

On Mon, Apr 07, 2025 at 01:35:00AM -0700, Nicolin Chen wrote:
> When falling back to standard SMMU CMDQ, impl_ops must be set to NULL, so
> tegra241_cmdqv_remove() will not be re-entered by arm_smmu_impl_remove(),
> which will trigger a UAF.
> 
> Fixes: 483e0bd8883a ("iommu/tegra241-cmdqv: Do not allocate vcmdq until dma_set_mask_and_coherent")
> Cc: stable@...r.kernel.org
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> index ce7be8eeb43c..8249ef087af3 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
> @@ -803,6 +803,7 @@ static int tegra241_cmdqv_init_structures(struct arm_smmu_device *smmu)
>  	dev_info(smmu->impl_dev, "Falling back to standard SMMU CMDQ\n");
>  	smmu->options &= ~ARM_SMMU_OPT_TEGRA241_CMDQV;
>  	tegra241_cmdqv_remove(smmu);
> +	smmu->impl_ops = NULL;
>  	return 0;

Per discussion in the other patch, with a v2 this whole rewind
part would be dropped to ask SMMU driver to fail and then call 
tegra241_cmdqv_remove() via smmu->impl_ops->device_remove().

So we wouldn't need this patch after all.

Thanks
Nicolin