Re: [PATCH 16/16] x86/amd_smn: Add support for debugfs access to SMN registers

[Borislav Petkov]

On Wed, Oct 23, 2024 at 05:21:50PM +0000, Yazen Ghannam wrote:
> +static ssize_t smn_value_write(struct file *file, const char __user *userbuf,
> +			       size_t count, loff_t *ppos)
> +{
> +	u32 val;
> +	int ret;
> +
> +	ret = kstrtouint_from_user(userbuf, count, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	add_taint(TAINT_USER, LOCKDEP_STILL_OK);

That looks like a TAINT_CPU_OUT_OF_SPEC to me.

> +	ret = amd_smn_write(debug_node, debug_address, val);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +DEFINE_SHOW_STORE_ATTRIBUTE(smn_node);
> +DEFINE_SHOW_STORE_ATTRIBUTE(smn_address);
> +DEFINE_SHOW_STORE_ATTRIBUTE(smn_value);
> +
>  static int amd_cache_roots(void)
>  {
>  	u16 node, num_nodes = amd_num_nodes();
> @@ -180,6 +257,12 @@ static int __init amd_smn_init(void)
>  	if (err)
>  		return err;
>  
> +	debugfs_dir = debugfs_create_dir("amd_smn", arch_debugfs_dir);
> +
> +	debugfs_create_file("node",	0600, debugfs_dir, NULL, &smn_node_fops);
> +	debugfs_create_file("address",	0600, debugfs_dir, NULL, &smn_address_fops);
> +	debugfs_create_file("value",	0600, debugfs_dir, NULL, &smn_value_fops);

Can we pls stick this behind a module param which is off by default? I don't
want that crap exposed even in debugfs, by default.

Thx.

-- 
Regards/Gruss,
    Boris.

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