Re: [PATCH v2] HID: rmi: check that report ids exist in the report_id_hash before accessing their size

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

On Jul 17 2014 or thereabouts, Andrew Duggan wrote:
> It is possible that the hid-rmi driver could get loaded onto a device which does not have the
> expected report ids. This should not happen because it would indicate that the hid-rmi driver is
> not compatible with that device. However, if it does happen it should return an error from probe
> instead of dereferencing a null pointer.
> 
> related bug:
> https://bugzilla.kernel.org/show_bug.cgi?id=80091
> 
> Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
> ---
> Added hid_err messages as suggested by Benjamin. This fixes the null pointer dereference from
> bug 80091 while the next patch addresses the binding issue in hid-core.

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

Cheers,
Benjamin

> 
>  drivers/hid/hid-rmi.c | 28 ++++++++++++++++++++++------
>  1 file changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/hid/hid-rmi.c b/drivers/hid/hid-rmi.c
> index 3221a95..260be7a 100644
> --- a/drivers/hid/hid-rmi.c
> +++ b/drivers/hid/hid-rmi.c
> @@ -848,6 +848,8 @@ static int rmi_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  	struct rmi_data *data = NULL;
>  	int ret;
>  	size_t alloc_size;
> +	struct hid_report *input_report;
> +	struct hid_report *output_report;
>  
>  	data = devm_kzalloc(&hdev->dev, sizeof(struct rmi_data), GFP_KERNEL);
>  	if (!data)
> @@ -866,12 +868,26 @@ static int rmi_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  		return ret;
>  	}
>  
> -	data->input_report_size = (hdev->report_enum[HID_INPUT_REPORT]
> -		.report_id_hash[RMI_ATTN_REPORT_ID]->size >> 3)
> -		+ 1 /* report id */;
> -	data->output_report_size = (hdev->report_enum[HID_OUTPUT_REPORT]
> -		.report_id_hash[RMI_WRITE_REPORT_ID]->size >> 3)
> -		+ 1 /* report id */;
> +	input_report = hdev->report_enum[HID_INPUT_REPORT]
> +			.report_id_hash[RMI_ATTN_REPORT_ID];
> +	if (!input_report) {
> +		hid_err(hdev, "device does not have expected input report\n");
> +		ret = -ENODEV;
> +		return ret;
> +	}
> +
> +	data->input_report_size = (input_report->size >> 3) + 1 /* report id */;
> +
> +	output_report = hdev->report_enum[HID_OUTPUT_REPORT]
> +			.report_id_hash[RMI_WRITE_REPORT_ID];
> +	if (!output_report) {
> +		hid_err(hdev, "device does not have expected output report\n");
> +		ret = -ENODEV;
> +		return ret;
> +	}
> +
> +	data->output_report_size = (output_report->size >> 3)
> +					+ 1 /* report id */;
>  
>  	alloc_size = data->output_report_size + data->input_report_size;
>  
> -- 
> 1.9.1
>