linux-kernel - Re: [PATCH v6 10/25] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE

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Message-ID: <20250616135837.GE1174925@nvidia.com>
Date: Mon, 16 Jun 2025 10:58:37 -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 v6 10/25] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC
 ioctl

On Sat, Jun 14, 2025 at 12:14:35AM -0700, Nicolin Chen wrote:
> +	/*
> +	 * FIXME allocation may fail when sizeof(*pages) * max_npages is
> +	 * larger than PAGE_SIZE. This might need a new API returning a
> +	 * bio_vec or something more efficient.
> +	 */
> +	pages = kcalloc(max_npages, sizeof(*pages), GFP_KERNEL);

Use the kvcalloc variation here then. You probably also need a
GFP_NOWARN to avoid syzkaller blowups.

> +	access = iommufd_hw_queue_alloc_phys(cmd, viommu, &base_pa);
> +	if (IS_ERR(access)) {
> +		rc = PTR_ERR(access);
> +		goto out_put_viommu;
> +	}
> +
> +	hw_queue = (struct iommufd_hw_queue *)_iommufd_object_alloc_ucmd(
> +		ucmd, hw_queue_size, IOMMUFD_OBJ_HW_QUEUE);
> +	if (IS_ERR(hw_queue)) {
> +		rc = PTR_ERR(hw_queue);
> +		goto out_destroy_access;
> +	}

I think these two are out of order, alloc the object first, then
do the access and set hw_queue->access. Make sure abort will clean it up
automatically when non-null and remove the out_destroy_access

Jason