linux-kernel - Re: [PATCH 4/4] platform/x86: Add Intel Software Defined Silicon driver

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Date:   Sun, 21 Nov 2021 13:31:25 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "David E. Box" <david.e.box@...ux.intel.com>
Cc:     lee.jones@...aro.org, hdegoede@...hat.com, bhelgaas@...gle.com,
        andriy.shevchenko@...ux.intel.com, srinivas.pandruvada@...el.com,
        mgross@...ux.intel.com, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 4/4] platform/x86: Add Intel Software Defined Silicon
 driver

On Sat, Nov 20, 2021 at 03:17:05PM -0800, David E. Box wrote:
> +static ssize_t registers_read(struct file *filp, struct kobject *kobj,
> +			      struct bin_attribute *attr, char *buf, loff_t off,
> +			      size_t count)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct sdsi_priv *priv = dev_get_drvdata(dev);
> +	void __iomem *addr = priv->regs_addr;
> +
> +	memcpy_fromio(buf, addr + off, count);

Oh nice, this will be fun if I provide "interesting" values for off to
the function right?

Remember:
	All input is evil.

> +
> +	return count;
> +}
> +static BIN_ATTR(registers, 0400, registers_read, NULL, SDSI_SIZE_REGS);
> +
> +static struct bin_attribute *sdsi_bin_attrs[] = {
> +	&bin_attr_registers,
> +	&bin_attr_state_certificate,
> +	&bin_attr_provision_akc,
> +	&bin_attr_provision_cap,
> +	NULL
> +};
> +
> +static ssize_t guid_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct sdsi_priv *priv = dev_get_drvdata(dev);
> +
> +	return sprintf(buf, "0x%x\n", priv->guid);

sysfs_emit() please.

These sysfs attributes are crazy.  Who has audited them to be correct
and work properly?  It feels like there are just buffer overflows
waiting to be exploited in them due to the reading/writing of raw memory
buffers all over the place.

Where is the userspace tool that uses these files?

thanks,

greg k-h