linux-kernel - Re: [PATCH V4 5/5] misc: mlx5ctl: Add umem reg/unreg ioctl

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Date: Thu, 29 Feb 2024 12:51:22 +0100
From: Vegard Nossum <vegard.nossum@...cle.com>
To: Saeed Mahameed <saeed@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Leon Romanovsky <leonro@...dia.com>, Jason Gunthorpe <jgg@...dia.com>,
        Jiri Pirko <jiri@...dia.com>, Leonid Bloch <lbloch@...dia.com>,
        Itay Avraham <itayavr@...dia.com>, Jakub Kicinski <kuba@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>, David Ahern <dsahern@...nel.org>,
        Aron Silverton <aron.silverton@...cle.com>,
        Christoph Hellwig <hch@...radead.org>, andrew.gospodarek@...adcom.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V4 5/5] misc: mlx5ctl: Add umem reg/unreg ioctl


On 07/02/2024 08:24, Saeed Mahameed wrote:
> +static int mlx5ctl_ioctl_umem_unreg(struct file *file,
> +				    struct mlx5ctl_umem_unreg __user *arg,
> +				    size_t usize)
> +{
> +	size_t ksize = sizeof(struct mlx5ctl_umem_unreg);
> +	struct mlx5ctl_fd *mfd = file->private_data;
> +	struct mlx5ctl_umem_unreg *umem_unreg;
> +	int err = 0;
> +
> +	if (usize < ksize)
> +		return -EINVAL;
> +
> +	umem_unreg = kzalloc(ksize, GFP_KERNEL);
> +	if (!umem_unreg)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(umem_unreg, arg, ksize)) {
> +		err = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (umem_unreg->reserved) {
> +		err = -EOPNOTSUPP;
> +		goto out;
> +	}
> +
> +	err = mlx5ctl_umem_unreg(mfd->umem_db, umem_unreg->umem_id);
> +
> +	if (!err && copy_to_user(arg, umem_unreg, ksize))
> +		err = -EFAULT;

Why do you copy this back to userspace, does it even change?

> +static struct mlx5ctl_umem *mlx5ctl_umem_pin(struct mlx5ctl_umem_db *umem_db,
> +					     unsigned long addr, size_t size)
> +{
> +	size_t npages = umem_num_pages(addr, size);
> +	struct mlx5_core_dev *mdev = umem_db->mdev;
> +	unsigned long endaddr = addr + size;
> +	struct mlx5ctl_umem *umem;
> +	struct page **page_list;
> +	int err = -EINVAL;
> +	int pinned = 0;
> +
> +	dev_dbg(mdev->device, "%s: addr %p size %zu npages %zu\n",
> +		__func__, (void __user *)addr, size, npages);
> +
> +	/* Avoid integer overflow */
> +	if (endaddr < addr || PAGE_ALIGN(endaddr) < endaddr)
> +		return ERR_PTR(-EINVAL);

There is a check_add_overflow() macro in <linux/overflow.h>, should that
be used instead?

> +
> +	if (npages == 0 || PAGES_2_MB(npages) > MLX5CTL_UMEM_MAX_MB)
> +		return ERR_PTR(-EINVAL);
> +
> +	page_list = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL_ACCOUNT);
> +	if (!page_list)
> +		return ERR_PTR(-ENOMEM);
> +
> +	umem = kzalloc(sizeof(*umem), GFP_KERNEL_ACCOUNT);
> +	if (!umem) {
> +		kvfree(page_list);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	umem->addr = addr;
> +	umem->size = size;
> +	umem->offset = addr & ~PAGE_MASK;
> +	umem->npages = npages;
> +
> +	umem->page_list = page_list;
> +	umem->source_mm = current->mm;
> +	umem->source_task = current->group_leader;
> +	get_task_struct(current->group_leader);
> +	umem->source_user = get_uid(current_user());

I think you could do this, right?

umem->source_task = get_task_struct(current->group_leader);
umem->source_user = get_current_user();

> +
> +	/* mm and RLIMIT_MEMLOCK user task accounting similar to what is
> +	 * being done in iopt_alloc_pages() and do_update_pinned()
> +	 * for IOPT_PAGES_ACCOUNT_USER @drivers/iommu/iommufd/pages.c
> +	 */
> +	mmgrab(umem->source_mm);
> +
> +	pinned = pin_user_pages_fast(addr, npages, FOLL_WRITE, page_list);
> +	if (pinned != npages) {
> +		dev_dbg(mdev->device, "pin_user_pages_fast failed %d\n", pinned);
> +		err = pinned < 0 ? pinned : -ENOMEM;
> +		goto pin_failed;
> +	}
> +
> +	err = inc_user_locked_vm(umem, npages);
> +	if (err)
> +		goto pin_failed;
> +
> +	atomic64_add(npages, &umem->source_mm->pinned_vm);
> +
> +	err = sg_alloc_table_from_pages(&umem->sgt, page_list, npages, 0,
> +					npages << PAGE_SHIFT, GFP_KERNEL_ACCOUNT);
> +	if (err) {
> +		dev_dbg(mdev->device, "sg_alloc_table failed: %d\n", err);
> +		goto sgt_failed;

Is this correct? See below...

> +	}
> +
> +	dev_dbg(mdev->device, "\tsgt: size %zu npages %zu sgt.nents (%d)\n",
> +		size, npages, umem->sgt.nents);
> +
> +	err = dma_map_sgtable(mdev->device, &umem->sgt, DMA_BIDIRECTIONAL, 0);
> +	if (err) {
> +		dev_dbg(mdev->device, "dma_map_sgtable failed: %d\n", err);
> +		goto dma_failed;
> +	}
> +
> +	dev_dbg(mdev->device, "\tsgt: dma_nents %d\n", umem->sgt.nents);
> +	return umem;
> +
> +dma_failed:
> +sgt_failed:
> +	sg_free_table(&umem->sgt);

Not sure about calling sg_free_table() if sg_alloc_table_from_pages()
failed.

> +	atomic64_sub(npages, &umem->source_mm->pinned_vm);
> +	dec_user_locked_vm(umem, npages);
> +pin_failed:
> +	if (pinned > 0)
> +		unpin_user_pages(page_list, pinned);
> +	mmdrop(umem->source_mm);
> +	free_uid(umem->source_user);
> +	put_task_struct(umem->source_task);
> +
> +	kfree(umem);
> +	kvfree(page_list);
> +	return ERR_PTR(err);
> +}


Vegard