AZL-97803

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

Input: synaptics-rmi4 - bound the F54 report size to the allocated buffer

rmif54work() reads a diagnostics report from the device into f54->reportdata, sizing the transfer with rmif54getreport_size():

report_size = rmi_f54_get_report_size(f54);
...
for (i = 0; i < report_size; i += F54_REPORT_DATA_SIZE) {
    int size = min(F54_REPORT_DATA_SIZE, report_size - i);
    ...
    rmi_read_block(.., f54->report_data + i, size);
}

reportdata is allocated once at probe from F54's own electrode counts (array3size(f54->numtxelectrodes, f54->numrxelectrodes, sizeof(u16))), but rmif54getreportsize() computes the size from drvdata->num*_electrodes when those are set, i.e. from the F55 function's electrode counts. Both counts come straight from device queries (F54 and F55 each report up to 255 electrodes) and nothing constrains the F55 counts to the F54 ones.

A malicious or malfunctioning RMI4 device that reports larger F55 electrode counts than its F54 counts makes reportsize exceed the allocation, so the read loop writes past reportdata (and the V4L2 dequeue memcpy() then reads past it). On conforming hardware the F55 configured electrodes are a subset of the F54 physical electrodes, so report_size never exceeds the buffer and well-behaved devices are unaffected.

Record the allocation size and reject a report that does not fit, mirroring the existing zero-size check.