Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

HID: rmi: fix OOB access with undersized RMI reports

The hid-rmi driver sizes its writeReport/readReport buffer purely from the report descriptor supplied by the device, with no minimum bound:

data->input_report_size = hid_report_len(input_report); data->output_report_size = hid_report_len(output_report); alloc_size = data->output_report_size + data->input_report_size; data->writeReport = devm_kzalloc(&hdev->dev, alloc_size, GFP_KERNEL); data->readReport = data->writeReport + data->output_report_size;

but then reads and writes fixed offsets into it. A device declaring a 1-byte output and a 1-byte input report makes hid_report_len() return 2 for each, so alloc_size is 4, while rmi_set_page() -- reached unconditionally at probe time through rmi_input_configured() -- stores writeReport[4] and rmi_hid_read_block() stores writeReport[0..5]. Since readReport lives at writeReport + output_report_size, those stores also corrupt the window the next reply is parsed out of.

The read path is worse: the copy length comes from readReport[1], which the device fills in and can be up to 255, and the copy starts at &readReport[2] with no regard for input_report_size, so it runs past the end of the allocation into adjacent slab objects. This does not even need a lying device -- rmi_f01_probe() issues a fixed 21-byte register read, so any device declaring an input report smaller than 23 bytes reads out of bounds e…