linux-kernel - Re: [PATCH v5 17/29] iommufd: Add mmap interface

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: <20250530162945.GF233377@nvidia.com>
Date: Fri, 30 May 2025 13:29:45 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, corbet@....net, will@...nel.org,
	bagasdotme@...il.com, robin.murphy@....com, joro@...tes.org,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	shuah@...nel.org, jsnitsel@...hat.com, nathan@...nel.org,
	peterz@...radead.org, yi.l.liu@...el.com, mshavit@...gle.com,
	praan@...gle.com, zhangzekun11@...wei.com, iommu@...ts.linux.dev,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
	mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com
Subject: Re: [PATCH v5 17/29] iommufd: Add mmap interface

On Sat, May 17, 2025 at 08:21:34PM -0700, Nicolin Chen wrote:
> +/*
> + * Helpers for IOMMU driver to alloc/destroy an mmapable area for a structure.
> + *
> + * To support an mmappable MMIO region, kernel driver must first register it to
> + * iommufd core to allocate an @out_offset, in the context of an driver-struct
> + * allocation (e.g. viommu_alloc op). Then, it should report to user space this
> + * @out_offset and the @length of the MMIO region for mmap syscall.
> + */
> +#define iommufd_viommu_alloc_mmap(viommu, member, mmio, length, out_offset)    \
> +	({                                                                     \
> +		static_assert(__same_type(struct iommufd_viommu,               \
> +					  viommu->member));                    \
> +		static_assert(offsetof(typeof(*viommu), member.obj) == 0);     \
> +		_iommufd_alloc_mmap(viommu->member.ictx, &viommu->member.obj,  \
> +				    mmio, length, out_offset);                 \
> +	})

Why is this like this? It's weird, just

static inline int iommufd_alloc_viommu_mmap(struct iommufd_viommu *viommu,
                                     phys_addr_t mmio_addr, size_t length,
                                     unsigned long *offset);

> +/* The vm_pgoff must be pre-allocated from mt_mmap, and given to user space */
> +static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct iommufd_ctx *ictx = filp->private_data;
> +	size_t length = vma->vm_end - vma->vm_start;
> +	struct iommufd_mmap *immap;
> +	int rc;
> +
> +	if (!PAGE_ALIGNED(length))
> +		return -EINVAL;
> +	if (!(vma->vm_flags & VM_SHARED))
> +		return -EINVAL;
> +	if (vma->vm_flags & VM_EXEC)
> +		return -EPERM;
> +
> +	/* vma->vm_pgoff carries an index to an mtree entry (immap) */
> +	immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff);
> +	if (!immap)
> +		return -ENXIO;
> +	/* Validate the vm_pgoff and length against the registered region */
> +	if (vma->vm_pgoff != immap->startp)
> +		return -ENXIO;

This check seems redundant

Jason