linux-kernel - Re: [PATCH v2 2/2] iommu/sva: Remove mm parameter from SVA bind API

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210415064459.GB1938497@infradead.org>
Date:   Thu, 15 Apr 2021 07:44:59 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, vkoul@...nel.org,
        Jason Gunthorpe <jgg@...dia.com>, zhangfei.gao@...aro.org
Subject: Re: [PATCH v2 2/2] iommu/sva: Remove mm parameter from SVA bind API

>   *
>   * Returns 0 on success and < 0 on error.
> @@ -28,6 +28,9 @@ int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
>  	int ret = 0;
>  	ioasid_t pasid;
>  
> +	if (mm != current->mm)
> +		return -EINVAL;
> +

Why not remove the parameter entirely?

> @@ -2989,8 +2990,11 @@ iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, unsigned int fla
>  		return ERR_PTR(-ENODEV);
>  
>  	/* Supervisor SVA does not need the current mm */
> -	if ((flags & IOMMU_SVA_BIND_SUPERVISOR) && mm)
> -		return ERR_PTR(-EINVAL);
> +	if (!(flags & IOMMU_SVA_BIND_SUPERVISOR)) {
> +		mm = get_task_mm(current);
> +		if (!mm)
> +			return ERR_PTR(-EINVAL);
> +	}

I don't see why we need the reference.  I think we should just stop
passing the mm to ->sva_bind and let the low-level driver deal with
any reference to current->mm where needed.