Re: [PATCH] HID: i2c-hid: Limit reads to wMaxInputLength bytes for input events

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

On Feb 20 2015 or thereabouts, Seth Forshee wrote:
> d1c7e29e8d27 (HID: i2c-hid: prevent buffer overflow in early IRQ)
> changed hid_get_input() to read ihid->bufsize bytes, which can be
> more than wMaxInputLength. This is the case with the Dell XPS 13
> 9343, and it is causing events to be missed. In some cases the
> missed events are releases, which can cause the cursor to jump or
> freeze, among other problems. Limit the number of bytes read to
> min(wMaxInputLength, ihid->bufsize) to prevent such problems.
> 
> Fixes: d1c7e29e8d27 "HID: i2c-hid: prevent buffer overflow in early IRQ"
> Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Thanks!
Benjamin

> ---
>  drivers/hid/i2c-hid/i2c-hid.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> index d43e967..5e72fc2 100644
> --- a/drivers/hid/i2c-hid/i2c-hid.c
> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> @@ -370,7 +370,10 @@ static int i2c_hid_hwreset(struct i2c_client *client)
>  static void i2c_hid_get_input(struct i2c_hid *ihid)
>  {
>  	int ret, ret_size;
> -	int size = ihid->bufsize;
> +	int size = le16_to_cpu(ihid->hdesc.wMaxInputLength);
> +
> +	if (size > ihid->bufsize)
> +		size = ihid->bufsize;
>  
>  	ret = i2c_master_recv(ihid->client, ihid->inbuf, size);
>  	if (ret != size) {
> -- 
> 1.9.1
>