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Message-ID: <20221013153730.rwtukjgpdgwgfodv@cantor>
Date: Thu, 13 Oct 2022 08:37:30 -0700
From: Jerry Snitselaar <jsnitsel@...hat.com>
To: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Lu Baolu <baolu.lu@...ux.intel.com>
Subject: Re: [RFC PATCH] iommu/vt-d: Add sanity check to
iommu_sva_bind_device()
On Thu, Oct 13, 2022 at 08:33:55AM -0700, Jerry Snitselaar wrote:
> iommu_sva_bind_device() should only be called if
> iommu_dev_enable_feature() succeeded. There has been one case already
> where that hasn't been the case, which resulted in a null pointer
> deref in dev_iommu_ops(). To avoid that happening in the future if
> another driver makes that mistake, sanity check dev->iommu and
> dev->iommu->iommu_dev prior to calling dev_iommu_ops().
>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
> ---
I don't know how many other drivers there will be in the future,
so quite possibly a non-issue. It did happen with the idxd driver
though, and I was thinking about that this morning so thought I
would send a patch to avoid it in the future.
Regards,
Jerry
> drivers/iommu/iommu.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 4893c2429ca5..20ec75667529 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2746,7 +2746,15 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void *drvdata)
> {
> struct iommu_group *group;
> struct iommu_sva *handle = ERR_PTR(-EINVAL);
> - const struct iommu_ops *ops = dev_iommu_ops(dev);
> + const struct iommu_ops *ops;
> +
> + if (!dev->iommu || !dev->iommu->iommu_dev) {
> + dev_warn(dev, "%s called without checking succes of iommu_dev_enable_feature?\n",
> + __func__);
> + return ERR_PTR(-ENODEV);
> + }
> +
> + ops = dev_iommu_ops(dev);
>
> if (!ops->sva_bind)
> return ERR_PTR(-ENODEV);
> --
> 2.37.2
>
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