Re: [PATCH v5 4/9] cxl/mem: Add basic IOCTL interface

From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Ben Widawsky <ben.widawsky@intel.com>
Cc: linux-cxl@vger.kernel.org, linux-acpi@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
	linux-pci@vger.kernel.org, Bjorn Helgaas <helgaas@kernel.org>,
	Chris Browy <cbrowy@avery-design.com>,
	Christoph Hellwig <hch@infradead.org>,
	David Hildenbrand <david@redhat.com>,
	David Rientjes <rientjes@google.com>,
	Jon Masters <jcm@jonmasters.org>,
	Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
	Rafael Wysocki <rafael.j.wysocki@intel.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	"John Groves (jgroves)" <jgroves@micron.com>,
	"Kelley, Sean V" <sean.v.kelley@intel.com>,
	kernel test robot <lkp@intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v5 4/9] cxl/mem: Add basic IOCTL interface
Date: Fri, 19 Feb 2021 20:22:00 -0500	[thread overview]
Message-ID: <YDBkOB3K8UqVakFf@Konrads-MacBook-Pro.local> (raw)
In-Reply-To: <20210217040958.1354670-5-ben.widawsky@intel.com>

..snip..
> +static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm,
> +					const struct cxl_mem_command *cmd,
> +					u64 in_payload, u64 out_payload,
> +					s32 *size_out, u32 *retval)
> +{
> +	struct device *dev = &cxlm->pdev->dev;
> +	struct mbox_cmd mbox_cmd = {
> +		.opcode = cmd->opcode,
> +		.size_in = cmd->info.size_in,
> +		.size_out = cmd->info.size_out,
> +	};
> +	int rc;
> +
> +	if (cmd->info.size_out) {
> +		mbox_cmd.payload_out = kvzalloc(cmd->info.size_out, GFP_KERNEL);
> +		if (!mbox_cmd.payload_out)
> +			return -ENOMEM;
> +	}
> +
> +	if (cmd->info.size_in) {
> +		mbox_cmd.payload_in = vmemdup_user(u64_to_user_ptr(in_payload),
> +						   cmd->info.size_in);
> +		if (IS_ERR(mbox_cmd.payload_in))
> +			return PTR_ERR(mbox_cmd.payload_in);

Not that this should happen, but what if info.size_out was set? Should
you also free mbox_cmd.payload_out?

> +	}
> +
> +	rc = cxl_mem_mbox_get(cxlm);
> +	if (rc)
> +		goto out;
> +
> +	dev_dbg(dev,
> +		"Submitting %s command for user\n"
> +		"\topcode: %x\n"
> +		"\tsize: %ub\n",
> +		cxl_command_names[cmd->info.id].name, mbox_cmd.opcode,
> +		cmd->info.size_in);
> +
> +	rc = __cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd);
> +	cxl_mem_mbox_put(cxlm);
> +	if (rc)
> +		goto out;
> +
> +	/*
> +	 * @size_out contains the max size that's allowed to be written back out
> +	 * to userspace. While the payload may have written more output than
> +	 * this it will have to be ignored.
> +	 */
> +	if (mbox_cmd.size_out) {
> +		dev_WARN_ONCE(dev, mbox_cmd.size_out > *size_out,
> +			      "Invalid return size\n");
> +		if (copy_to_user(u64_to_user_ptr(out_payload),
> +				 mbox_cmd.payload_out, mbox_cmd.size_out)) {
> +			rc = -EFAULT;
> +			goto out;
> +		}
> +	}
> +
> +	*size_out = mbox_cmd.size_out;
> +	*retval = mbox_cmd.return_code;
> +
> +out:
> +	kvfree(mbox_cmd.payload_in);
> +	kvfree(mbox_cmd.payload_out);
> +	return rc;
> +}

..snip..

> +static int cxl_query_cmd(struct cxl_memdev *cxlmd,
> +			 struct cxl_mem_query_commands __user *q)
> +{
> +	struct device *dev = &cxlmd->dev;
> +	struct cxl_mem_command *cmd;
> +	u32 n_commands;
> +	int j = 0;

How come it is 'j' instead of the usual 'i'?
> +
> +	dev_dbg(dev, "Query IOCTL\n");
> +
> +	if (get_user(n_commands, &q->n_commands))
> +		return -EFAULT;
> +
> +	/* returns the total number if 0 elements are requested. */
> +	if (n_commands == 0)
> +		return put_user(cxl_cmd_count, &q->n_commands);
> +
> +	/*
> +	 * otherwise, return max(n_commands, total commands) cxl_command_info
> +	 * structures.
> +	 */
> +	cxl_for_each_cmd(cmd) {
> +		const struct cxl_command_info *info = &cmd->info;
> +
> +		if (copy_to_user(&q->commands[j++], info, sizeof(*info)))
> +			return -EFAULT;
> +
> +		if (j == n_commands)
> +			break;
> +	}
> +
> +	return 0;
> +}
> +
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