linux-kernel - Re: [PATCH v9 10/17] platform/x86: dell-smbios-wmi: Add new WMI dispatcher driver

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Date:   Tue, 17 Oct 2017 21:10:44 +0200
From:   Pali Rohár <pali.rohar@...il.com>
To:     Mario Limonciello <mario.limonciello@...l.com>
Cc:     dvhart@...radead.org, Andy Shevchenko <andy.shevchenko@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>, quasisec@...gle.com,
        rjw@...ysocki.net, mjg59@...gle.com, hch@....de,
        Greg KH <greg@...ah.com>, Alan Cox <gnomes@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v9 10/17] platform/x86: dell-smbios-wmi: Add new WMI
 dispatcher driver

On Tuesday 17 October 2017 13:21:54 Mario Limonciello wrote:
> +static LIST_HEAD(wmi_list);
> +
> +static inline struct wmi_smbios_priv *get_first_smbios_priv(void)
> +{
> +	return list_first_entry_or_null(&wmi_list,
> +					struct wmi_smbios_priv,
> +					list);
> +}

...

> +int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
> +{
> +	struct wmi_smbios_priv *priv;
> +	size_t difference;
> +	size_t size;
> +	int ret;
> +
> +	priv = get_first_smbios_priv();

Mutex needs to be acquired before calling this function. Otherwise there
is a race condition between removing element from the list returned by
this call and later usage of structure priv.

> +	if (!priv)
> +		return -ENODEV;
> +
> +	size = sizeof(struct calling_interface_buffer);
> +	difference = priv->req_buf_size - sizeof(u64) - size;
> +
> +	mutex_lock(&call_mutex);
> +	memset(&priv->buf->ext, 0, difference);
> +	memcpy(&priv->buf->std, buffer, size);
> +	ret = run_smbios_call(priv->wdev);
> +	memcpy(buffer, &priv->buf->std, size);
> +	mutex_unlock(&call_mutex);
> +
> +	return ret;
> +}

-- 
Pali Rohár
pali.rohar@...il.com