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

From: Andrew Duggan
Date: Thu Jul 17 2014 - 19:22:38 EST


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@xxxxxxxxxxxxx>
---
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.

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

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