linux-kernel - Re: [PATCH v10 10/10] iommu/vt-d: Add iotlb flush for nested domain

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Date: Tue, 2 Jan 2024 14:44:22 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Yi Liu <yi.l.liu@...el.com>
Cc: joro@...tes.org, alex.williamson@...hat.com, kevin.tian@...el.com,
	robin.murphy@....com, baolu.lu@...ux.intel.com, cohuck@...hat.com,
	eric.auger@...hat.com, nicolinc@...dia.com, kvm@...r.kernel.org,
	mjrosato@...ux.ibm.com, chao.p.peng@...ux.intel.com,
	yi.y.sun@...ux.intel.com, peterx@...hat.com, jasowang@...hat.com,
	shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
	suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	zhenzhong.duan@...el.com, joao.m.martins@...cle.com,
	xin.zeng@...el.com, yan.y.zhao@...el.com, j.granados@...sung.com
Subject: Re: [PATCH v10 10/10] iommu/vt-d: Add iotlb flush for nested domain

On Tue, Jan 02, 2024 at 06:38:34AM -0800, Yi Liu wrote:

> +static void intel_nested_flush_cache(struct dmar_domain *domain, u64 addr,
> +				     unsigned long npages, bool ih, u32 *error)
> +{
> +	struct iommu_domain_info *info;
> +	unsigned long i;
> +	unsigned mask;
> +	u32 fault;
> +
> +	xa_for_each(&domain->iommu_array, i, info)
> +		qi_flush_piotlb(info->iommu,
> +				domain_id_iommu(domain, info->iommu),
> +				IOMMU_NO_PASID, addr, npages, ih, NULL);

This locking on the xarray is messed up throughout the driver. There
could be a concurrent detach at this point which will free info and
UAF this.

This seems to be systemic issue, so I'm going to ignore it here, but
please make a series to fix it completely.

xarray is probably a bad data structure to manage attachment, a linked
list is going to use less memory in most cases and you need a mutex
lock anyhow.

Jason